PDA

View Full Version : TR2/3/3A Buffing out paint.



sp53
06-26-2018, 10:41 AM
Buffing out paint. John gave an excellent over view of how to buff out paint, but I did not want it to stop there. My problem is I am getting cold feet when I think about putting sand paper on this new paint or going after it with a buffer, so please tell me some stories and maybe I can synthesize more knowledge and stop being so chicken. I plan on starting on the wheel wells of the tub that I painted last year to get the feel for it. At HF they had those foam pads in 3 different textures(not cheap for there); the body shop had these wool buffers made of wool, but no cotton. Some had padding on both sides with an arbor and there was also a single sided wool Velcro so I bought one. I think it would be better to buy John a plane ticket.

If I do the inside of the tub, should I put some compound on the paint or the buffer and how would I get water in there without making a huge mess. There is probably no way of not making a mess. The u-tube videos are informative but I have gotten some bad ideas from there also. I am probably over thinking this again, but I need a push sometimes.
Pease out

CJD
06-26-2018, 10:53 AM
Wool is good! See, my memory is going bad, as they look like cotton, but are wool! Sorry about that. I always use the double sided. They are not cheap, but a pad will last a couple cars, and even some other projects in between. Last month we buffed our marble tile with the hand buffer getting the house ready to sell. Funny thing is that, after trying all those fancy polishes for floors, the automotive polish was the best.

Buffing enlvolves a subtle tilting of the buffer as you continually move it in a back and forth motion. If you watch a floor buffer in operation, you will see the guy tilting it just enough that the pad spin aides in moving it in the direction desired. The tilt helps you buff, instead of making you fight the buffer. The tilting also helps change the direction of the swirls, so they average out.

You can practice your initial buffing on an old panel...or even a primed one. It only takes a few minutes to get the feel, and after that it’s like riding a bike. It can be a challenge until you understand how to tilt it, with you fighting to get it going where you want...but as soon as you master the tilt it is a no-brainer from then on.

Finally, after the initial “touch down”, when you try to prevent the polish from spraying all over, I normally lock the trigger on high as I buff. It’s just one less thing to think about when the speed is constant. The only hard fast rule is to keep the buffer moving. If you stop it will start to dig into the paint...so always moving until you either stop the spin or lift it off.

sp53
06-26-2018, 02:44 PM
Ok John and thanks for taking some of the edge off, I really appreciate you taking the time to write. Let’s say for example, I start on these wheel wells. Should I use a spongy to get them wet or is the liquid solution in the compound enough; it looks very liquidly. Should I apply the compound to the buffer dry? How much compound should I put on? The videos use just a little. The area I am going to start on is going to be hidden, but my inexperience has me at a loss.

CJD
06-26-2018, 02:54 PM
Buffing is done dry. The only moisture is from the polish, and even then only about a nickel sized drop will last a couple minutes of buffing. I have never used sponge pads...and off-hand I think they would be too coarse for what we are doing. If you finish sand with 1000-2000grit wet, then a sponge would be going backwards. Of course there may be someone out there with experience with sponge pads??

If the pad gets too wet, then the little “wool!!” threads start to cake together. You want them to be free to move for the most part. So if they get caked together, then that is when you flip the buffer over on a table, lock it on high speed and run the screw driver tip back and forth to “comb” the little threads back apart.

Keep a dry, clean towel nearby to clear off the buffing residue, dust, and wool that flings off. When you think you are about done, wipe dry with the towel to be able to see clearly...and decide where and how much it needs to be buffed.

I just apologize that I never got a chance to post buffing on my project. Most of the panels came out well...but I do need to buff the boot lid and parts of the rear scuttle.

Last thought...how long will you need to spend on a panel?? If you use the sanding technique to prep before the buffing, you should be able to complete a boot lid in about 5 minutes. If you have a bad spot, then re-sand just that area wet, and then dry it back off and start over with the buffer and polish. The sanding just reduces the time you have to buff. Also, if you try to buff too much (i.e too deeply), the buffer tends to leave waves in the work. Sanding is less likely to leave any waviness, so repeat the sanding until you like the area...or you think you are getting thin.

sp53
06-26-2018, 04:09 PM
Thanks again John, what I have mostly is orange peel and a few dull spots, but there is one run on a rear fender plus that is the one with only 2 coats. The paint I chose was enamel with 8 to 1 hardener. It was the least expensive, but for me it looks more original. I went to this car museum in Montana or Wyoming and they had all these old 1950 cars with original paint. Looking at one of those just took me back to a time of 2 tone paint jobs that looked strong and durable. The paint guys told me it will fade quickly, but the paint I chose will have more of that look.

When I get to the run, I will be asking more questions. My gut tells me to wet sand with 500 to get the bulk of the extra paint off and then try and feather it in with the buffer, but only a guess. Thanks again for the time it should take to do a panel. It is those little things that people with experience sometimes forget to share. That is why I keep track of the amount of paint I mix, so maybe someone can use that knowledge because this is my first time and I was very concerned with that. I might try the refrigerator idea sometime also.
peace out

PC
06-26-2018, 07:48 PM
Forgive me, but this thread reads like there’s already been a whole lot of discussion that I missed. So I don’t know what’s been said, what hasn’t, and where I might be of some help. So If I say something way off base I apologize.

If I’m reading this right, it sounds like you have a single stage finish. Not that it would change how you approach the sand, cut and buff process verses a base/clear finish. But single stage finishes do tend to be more forgiving.

I don’t know what products you already have or what you have readily available so I’ll just assume nothing.

Be sure the runs are cured before you try removing them. They are thick and can still be gummy even after the rest of the finish has hardened.

When it comes to sanding, always use abrasives that are specifically designed for paint finishing. You will save yourself a whole lot of work and produce vastly better results. Ordinary abrasives leave a very inconsistent scratch pattern that is nearly impossible to buff out completely. Specialized abrasives like Meguiar’s Uni-grit, 3M Trizact, Mirka Abralon, etc. cost more up front but save you in long run. They last longer and finish out with much less work.

Your paint’s manufacturer probably has specific recommendations for abrasive grades. I would be surprised if they recommend anything coarser than #800.

Machine sanding (with a short throw DA sander designed for finish work) always leaves a finer scratch that’s easier to buff than hand sanding.

Buffing pads are just like any other tools. There are good ones and not so good ones. I would recommend sticking with name brands like Meguiar’s, 3M or Lake Country.

Wool pads cut faster than foam. They also build up less heat so they’re a bit more forgiving of technique. They’re usually the first choice for removing sanding scratch. As a noobie you’re guaranteed to get heavy swirling. Even experienced operators will get at least some swirling with wool. So if you want the best possible finish you’ll want to follow with foam. And to be absolutely swirl free, that last foam step is often best done with a DA buffer.

Note: this is why body shops almost always do terrible polish work. Most use rotary/wool exclusively just because it’s faster.



about 40 seconds into this clip, Autogeek's Mike Phillips shows how to pick up a bead of compound without splatter:

https://www.youtube.com/watch?v=PqTnIefWRg8

M_Pied_Lourd
06-26-2018, 10:19 PM
For some reason, I have never had much success with a da buffer/polisher. I have a porter cable one but can never get as good a finish as I get with my Milwaukee 7" polisher and foam pads.

The da buffer polishers are definitely much safer to use for novices as improper/over aggressive use of the regular polisher can lead to heavy swirls and burn through on flat surfaces and particularily unprotected edges...

Cheers
Tush

PC
06-27-2018, 02:05 AM
The older, shorter throw, lower powered DA's like the Porter-Cable 7424 are somewhat limited in their capacity, especially with harder urethane finishes. To remove defects you may have to shrink your working area, use smaller pads and slow your hand speed. You really have to use the right pads, too. The white, screw-in pad that Porter-Cable supplies is completely worthless.

The capability of those DA's can be extended considerably by using the current crop of microfiber pads.

The newer, longer throw, higher powered DA's are much more capable. A lot of guys rarely use their rotaries any more.

TomMull
06-27-2018, 09:25 AM
For some reason, I have never had much success with a da buffer/polisher. I have a porter cable one but can never get as good a finish as I get with my Milwaukee 7" polisher and foam pads.

The da buffer polishers are definitely much safer to use for novices as improper/over aggressive use of the regular polisher can lead to heavy swirls and burn through on flat surfaces and particularily unprotected edges...

Cheers
Tush

There is a bit of a learning curve to buffing so sp53 is wise to start where it doesn't show as much. If you are confident with the tool you have used in the past by all means use it. Of course there are lots of places on our LBCs where the big Milwaukee won't go. Also the pad can make as much of difference as the tool. I'm starting to like the bumpy foam things for the da. (Probably been around for decades but I just got some.)
54300
Tom

M_Pied_Lourd
06-27-2018, 08:15 PM
The older, shorter throw, lower powered DA's like the Porter-Cable 7424 are somewhat limited in their capacity, especially with harder urethane finishes. To remove defects you may have to shrink your working area, use smaller pads and slow your hand speed. You really have to use the right pads, too. The white, screw-in pad that Porter-Cable supplies is completely worthless.

The capability of those DA's can be extended considerably by using the current crop of microfiber pads.

The newer, longer throw, higher powered DA's are much more capable. A lot of guys rarely use their rotaries any more.

Agreed. Be been using the "chemical guys " foam pads...the porter cable ones are garbage.

Cheers
Tush

sp53
06-27-2018, 10:06 PM
Well I gave the buffing a go, but not happy with the results. I am going to take one of the doors down to the body shop and ask what product they suggest. The stuff I have is too watery. I ask them about the 3M finesse product, but they would have to order it. They did say 3M was the best and I should use the best. I am still chicken, but did try and knock down a couple of the paint cruds, so I am warming up to it. Thanks for the video with the 10:00 o clock idea because what I was able to do good was throw the polishing solution all over.
Pease out

PC
06-28-2018, 01:32 AM
…. The stuff I have is too watery….
Exactly what did you use? What were you trying to accomplish? What was the result?



…. I ask them about the 3M finesse product, but they would have to order it. …
I find that rather odd. In this industry 3M products are about as common as air. What do they keep on hand?



…. They did say 3M was the best and I should use the best.…
I’ll agree with the second part. The first part is entirely a matter of opinion.

Not saying it’s wrong, just that everybody in the biz has their own opinion. And you know what they say about opinions.



… but did try and knock down a couple of the paint cruds, so I am warming up to it. …
What kind of paint defects? Runs? Blobs? Fisheyes? The buffer is the wrong tool for those. They need to be sanded or scraped off before buffing.

sp53
06-28-2018, 09:06 AM
I probably made these 3 posts confusing by compartmentalizing them into individual posts: like- over spray, compressor crud, and buffing out paint. What I am trying accomplish in this post is to get the orange peel off and remove some very small little cruds that came out of the paint gun when spraying. My best guess on those cruds are unstrained paint. I took a small piece of wet 500 and very very carefully by hand knock them down to just about the plane surface of the paint job. They were maybe 1/32to 1/16 around. My concern was they would fly out leaving a small crater behind.

steve

CJD
06-28-2018, 09:39 AM
When I was in the AF I took my prized ‘67 Camaro to be painted by Tonti Body and Fender in New Orleans. They had repaired cars for my family for a couple generations, and were almost like part of the family. The Camaro was painted in straight enamel, so needed at least a couple months to harden before buffing. I begged Kenny to buff it early, as I didn’t have much time off to come back and get the car...being based in Mississsippi. I told him I would help. He finally relented, so I got to watch pros buff a car. I tried a little with the buffer, and was warned to stay away from the edges. Of course I goofed and went right through one edge in a flash!!

Anyway...Kenny used the Finesse, and that is what I always used afterward. It takes so little that a bottle usually lasts me a decade or more. I have tried other compounds, but never found any better...as I said, it even beat the best floor products for buffing our tile! One bottle I bought was FinesseIII. I think it was less abrasive, and still worked, but not quite as fast as the straight Finesse.

If you have the panel lightly trued-up and worked down to the 1500-2000 grit, then the buffer with wool will almost finish the job with no compound. It takes very little. Over the 5 minutes or so it takes to buff a door, you might put about 3 dime to nickel sized drops of compound. You will likely have to clean the pad once, before doing the final light buff to bring the panel to perfect shine.

I wouldn’t worry about the dirt breaking out. By the time the dirt sits in the paint and goes through the gun it will be tinted throughout! You may see a very small color difference once it is sanded down and buffed. An interesting thing about the human eye...unless a spot is obviously a flaw, everyone that sees a very small spec IN the paint will naturally assume it is just dirt ON the paint. It will bother you more than anyone looking at the car.

PC
06-28-2018, 01:42 PM
…. was warned to stay away from the edges. Of course I goofed and went right through one edge in a flash!!...
Excellent point.

Steve, when buffing the flat areas it’s best to avoid the edges completely. Some guys even mask them off. Then, when it’s time to do them, slow the buffer speed down, pay very, very close attention and tilt the buffer slightly so that you always buff off the edge. Never buff into the egde.





…I wouldn’t worry about the dirt breaking out. ….

Ditto.

Steve, If you have air filters in your lines and you work with clean tools you shouldn’t get any dirt in your paint. Dust nibs occur when a speck of dirt lands on the wet paint and warps the surface tension of the wet film. The dirt will still be on top but there will be a slight bump around it. Dust nibs can be removed with de-nibbing tools or abrasives.




…. I took a small piece of wet 500 …
I would caution against using #500. You’re just making more work for yourself. Since you’re concentrating all your energy a very tiny area you can typically work blemishes out with #1000 or #1500. That leaves only #1000 scratch to buff out.





https://www.britishcarforum.com/bcf/attachment.php?attachmentid=54314&d=1530191094


Holy Jurassic Park, Batman! You can still get that stuff?

Seriously, I was cleaning out my parents’ garage a couple years back and found my 30+ year old of bottle of it. I posted pix on another car forum and got laughs form a couple of other geezers and dazed confusion from the youg’uns.

As the saying goes, “Well, there’s your problem.”

Not saying that it’s a bad product, only that you need to understand why it exists and what its capabilities are. I’m pretty sure it was created during the Bronze Age to polish lacquer on Trojan chariots.

Let’s take a step back and try to get a little perspective on what you’re trying to accomplish.

Basically, you’re trying to smooth out your paint to the point where surface imperfections are imperceptible. You have a variety of tools, chemical and mechanical, of varying capabilities at your disposal. As with any tool, you’ll get the best results by matching the tool and technique to the task at hand. Some of those tools will remove larger imperfections quickly but leave telltale imperfections of their own. Others can remove very small imperfections.

This analogy may not be exactly to scale mathematically, but I think you’ll get the idea:

Think of your paint as if it were your garden. And you want it really flat and smooth so you can install a putting green. You’ve brought in loads of new, clean soil and it’s piled up and lumpy. You need to grade it out.

Blemishes like runs and dust nibs are like dirt piles about the size of your house. You could theoretically smooth them out with one of these.
https://images-na.ssl-images-amazon.com/images/I/31BH%2BbvOciL._SL500_AC_SS350_.jpg

But really, you should probably use one of these:

https://i.ytimg.com/vi/3KQibfmLf0A/hqdefault.jpg or https://s7d2.scene7.com/is/image/Caterpillar/C10337180?$cc-g$

These are the equivalent of say #800 sandpaper.


Orange peel is about the size of a shed. Good tools for this would be:

https://www.nolabobcat.com/wp-content/uploads/2012/06/bobcat_t300_track_loader1.gif or https://i.ytimg.com/vi/v8WNSBqCpwU/hqdefault.jpg

These would be about #1000 to #1500 sandpaper.

Now that you have the piles flattened out it’s time to smooth the surface with very fine abrasives, compounds and polishes. They would be more like:

https://i5.walmartimages.com/asr/b2af42ea-8c6d-4326-8c8c-eb9f03fb79b0_1.fdb36fb7d51f181158c4cb79159de7f5.jp eg?odnHeight=450&odnWidth=450&odnBg=FFFFFF and https://images-na.ssl-images-amazon.com/images/I/51WYcm77TiL._SX355_.jpg



Liquid Ebony is a product called a glaze. Glazes aren’t really meant to remove defects. They’re intended to be sort of a final accent to an already defect-free finish. In our lawn analogy they would be about like this:


https://www.zitomer.com/media/catalog/product/cache/image/265x265/57a0f909ed33adbde743dbde34d20fc7/K/E/KENT_POCKETCOMB_FOT_amended.jpg

sp53
06-28-2018, 07:11 PM
Well that is funny I enjoyed it. Thankfully I never used any of Ebony stuff. I got it from a guy who painted car for me years ago. I have been looking into the 3M products and the 3M polishing solution has changed at some point and is still evolving. I have been looking at the “3M finesse 11” on line and can get pint for 25.00 at a shop in town. This is the black bottle with white a label. The shop I have been doing business carries a “3M Perfect- It” in a purple bottle for 60.00 a quart, and they used to have the black bottle 3M . The purple stuff is on line also for more money and shipping. They tell me that the old 3M Finesse is now the improved purple “3M Perfect it” I am totally cool with getting the pint in the black bottle because that is probably all I will need, but it is the number 3M Finesse 11, so does the number 2 stuff sound correct?

bnw
06-30-2018, 09:07 AM
Back in 1992, I painted my TR6 with Centari enamel with hardener. I had some orange peel on the bonnet but what aggravated me the most was the dust I got on the horizontal surfaces in spite of my home made ventilated booth. I too, was afraid to wet sand my glossy but flawed finish. I waited a year before I went after it. Not sure what products I used but the end result was spectacular. What I lost, was the built in gloss and had to wax/polish at least once a year. It was well worth it. and, stay away from the edges!

PC
06-30-2018, 08:08 PM
Steve,

I don't have personal experience with 3M compounds and polishes so I can't make specific recommendations about them.

What I can say is that you need to be very careful to be very, very specific about what you buy, how it's intended to be used and what you expect to accomplish with it. 3M's product branding and naming conventions are very confusing and people in the body and collision industry are notoriously cavalier about the accuracy of the names they throw around when making product recommendations.

If someone says to get a bottle of Finesse-It or Perfect-It they are basically giving you no useful information. Those are brands, entire product lines, not specific products. In liquids alone, within Perfect-It you have EX Rubbing Compound, EX Machine Polish, Machine Polish, Finishing material, EX Ultrafine Machine Polish and Denibbing Polish. And Finesse-It has SRC Machine Polish, Purple, Finishing Material, Extra Fine, K211, Final Finish, and Ultra Fine.

It's all too easy to pick up the wrong product and/or wrong advice for you're doing. You need to be clear and concise when communicating with people.

sp53
06-30-2018, 08:24 PM
I took the worst of the fenders, the one with the run to experiment and get a feel for the buffer. My fear is the fender is going to need a re-spray anyway because the there is a small section at the very rear that looks like there is no paint only gray primmer.

Anyways, I sanded the run with some very wet 1000, and the run came right out no problem, so then I sanded the dull areas also with 1000 wet and they came out, and it looked like things were going good, so I started to buff with the 3M Finesse ll to see where I was at. The problem I am having now is the orange peel looks to be very deep and is not coming out. However, at the run area where the orange peel was just as deep and I sanded more it looks like more of the orange peel came out. I am not sure what the problem is, but my gut tells me to wet sand the fender more with 500 or 1000 a lot more then go the buffer. I do not have any 2000 or 1500 and will get some Monday when the store opens to work on the pieces that are not as bad; the pictures are from the same spot.

steve

CJD
06-30-2018, 09:42 PM
If the buffer seems to “add” orange peel, then the paint may need more time to cure before buffing. If it is soft, the heat from the buffer can actually move the paint around, making waves on the surface.

If you think the paint is solid, and well past the recommended curing time, then “yes”, you may need to go a tad deeper with the paper.

500 grit is on the rough side for buffing...but you can make it work by rubbing two sheets against each other to smooth out the grit...and then using the paper for a long time. You know how it is...old 500 grit is closer to fresh 800 grit...so you can make it work.

The pros I watched only used 600 grit, and then went right to the buffer. I’ve tried that, and it does work, but you have to spend more time and more compound to remove the 600 grit swirls. Working through 600 to 1000, 1500, etc. is just a technique I started picking up to reduce the buffing time.

You are doing great...it’ll start to come together and make sense as you do it more!

PC
07-01-2018, 12:21 AM
.... I sanded the run with some very wet 1000, and the run came right out no problem, so then I sanded the dull areas also with 1000 wet and they came out, and it looked like things were going good, so I started to buff with the 3M Finesse ll to see where I was at. The problem I am having now is the orange peel looks to be very deep and is not coming out. However, at the run area where the orange peel was just as deep and I sanded more it looks like more of the orange peel came out. I am not sure what the problem is, but my gut tells me to wet sand the fender more with 500 or 1000 a lot more ...
If the runs came out with #1000 then you surely don't need (and definitely don't want) to sand the orange peel with #500. What kind of sanding block are you using?



...The pros I watched only used 600 grit, and then went right to the buffer....
That was common a long, long time ago when finer grit abrasives weren't common and very soft paints like lacquers and high solvent enamels were.

Nowadays you only see that in high volume collision repair where they get paid by the job, not the hour and quality expectations are very low. They'll cut any corners they can knowing that few customers can tell the difference.




.... Working through 600 to 1000, 1500, etc. is just a technique I started picking up to reduce the buffing time. ...

It also raises quality substantially. Which is why every paint manufacturer calls it out in their process instructions.

sp53
07-01-2018, 09:09 AM
What I used was 1000 paper folded around a rectangular very soft wet sponge. I tried to free hand the paper but was getting very small lines from the edge of the paper; they came right out, but that is what moved me to the sponge. The product information sheet says 16 hours at 70 degrees to polish and put into service, so I believe the paint is cured. Today I am going to use the 1000 again and just do more work with it and change the paper more and then try some more buffing. I did however use too much buffing compound, so maybe that is why I am not cutting down. I laid a pencil size bead about 6 inches long which is a lot more that suggested. Coming in at 10:00 o’clock made the compound stay on the panel better

The paint must be soft because the run came out with not too much work, maybe 5 minutes. Perhaps the sponge block is too soft and I should try one of my soft blocks to get the high points off the peel more evenly. I went with the sponge because of the constant water coming out plus I felt it would have less of a chance cutting into curve on the panel.

CJD
07-01-2018, 09:35 AM
PC...I’ve never seen process instructions. Is that different from the data sheet? I’ve been using PPG with the DCU clear for a decade or so. On those data sheets it says when you can buff, but doesn’t specify any paper recommendations. Am I missing another sheet...I love studying tech sheets!?!

sp53
07-01-2018, 02:39 PM
The 3M Finesse ll part number I am using is #39003. It came highly recommended for what I am doing.

PC
07-01-2018, 04:28 PM
I said process instructions as a sort of generic way of referring to wherever the manufacturer chooses to put that info. It's often in the data sheets but not always. Some manufacturers put in in separate publications and some seem to leave out bits here and there. There's no consistency across the industry or sometimes even across product lines from one manufacturer.

As you point out, PPG doesn't even mention sanding in DCU data sheets. But in the sheet for DC CeramiClear they call out P800 - P1200.

PC
07-01-2018, 05:03 PM
The 3M Finesse ll part number I am using is #39003. It came highly recommended for what I am doing.

Good luck, hope it works out. Keep us posted.

Interestingly, If you do a search for 39003 on 3M's website, nothing shows up in the way of instructions or technical descriptions. Only the SDS comes up.

The only thing even vaguely resembling something useful I found was the short description at detailing.com (https://www.detailing.com/store/3m-finesse-it-ii-finishing-material-machine-polish-39003-16-oz.html):

Description:


3M Finesse-It II Finishing Material Machine Polish, 39003 - 16 oz.

Is an entry level machine polish designed for us on OEM and fully cured automotive paints. Removes microfine scratches and swirl marks while leaving a high gloss finish. Quickly and effectively removes minor scratches, producing a brilliant, deep, wet look shine. For best results use by machine. Contains no wax or silicone and is clear coat safe.

Directions:




Shake container well before using.
Apply enough polish to work a 2' by 2' area
Polish area using light to medium pressure. Reduce pressure as material begins to dry and polish to a high gloss.
Remove spatter from adjacent panels before polishing the next panel.

sp53
07-01-2018, 08:56 PM
Well things were going kinda good on my sacrificial panel, but not perfect. I sanded 2 more times with the 1000 paper and buffed. This time I cut the paper into an oval shape so not to have any edges. Then sanded by hand. I got some areas to look perfect with no orange peel and high gloss, but in one spot I got some paint build up and sanded again and buffed again, but this time I started going through. I could see some gray shadow it would no show in the pictures.

I took the panel outside from the well light garage to see better and in the sun light the panel looked excellent other than the burn through and the spot I missed in the initial painting, so the panel will be a re-spray, but again it only had 2 coats because I ran out of paint and it had a run, so I knew I was in trouble, but did not I could fix it!

On the next one, I will start sanding with 1500 or 2000 to knock the paint down like John suggested using the oval shaped paper because I was able to get an evener dulling of the finish that way. You are correct bnw it is so painful to take the shine off, and thanks bnw for your story I was able to work that in and gain some knowledge and comfort.
Moreover, thanks PC for the 10:00 clock tip and info page that sure saved some material flying around the room.

My foundation is still rocky but that is better than sand, and I might be getting it a little, but every time I thought that I had it, I would burn through or something. So John what causes “Orange Peel” anyway too much air pressure, crappie paint, not moving fast enough when painting or all the above?

CJD
07-01-2018, 09:36 PM
Well, on the bright side, that panel should be perfect after the next spraying!

The short answer for orange peal is the paint is drying on the panel before it has an opportunity to flow into itself. The cause can be simple, or complex...

1). If you are spraying dry, by having the paint control turned too low or wrong air pressure.
2). Moving the gun too fast, or at an angle other than perpendicular.
3). Painting with too cold of a reducer (cold is designed to evaporate quicker than warm reducers).
4). Painting in too high a temperature or spraying in direct sunlight.

It could be one or all of the above causing your peel. I would start by carefully reviewing the data sheet for your paint, to make sure your reducer is correct for the temperature you will spray, your tip is in the recommended size range, and your air pressure is good with the trigger pulled.

Remember Low Pressure High Volume is a bit of a misnomer. The low pressure is at the tip, but hose pressure will still be considerably higher. I run 90 psi in the hose, all the way to the gun. I then use a small regulator at the gun inlet. The small reg reads 90 when the trigger is off...but with the trigger pulled I adjust to read 16-22psi. That number usually comes off the data sheet. If there is no number on the sheet, then I default to about 20 psi.

If you get the above dialed in, then you should have eliminated every issue down to your spraying technique.

I always start my spray by having a cardboard box or the like to set up the spray pattern and paint amount. Use the box to set the paint control to the speed you want to comfortably sweep each pass over the panel. If you use a round pattern, you get a lot of paint on one spot. If you add air to the fan control, then the paint will reduce, so you have to bump it back up. When all is good, you should be able to move at a comfortable speed across your work, and leave a nice, wet stripe.

Keep the gun perpendicular as you sweep along the panel. Plan ahead how you will work edges and all in. If you do an edge, and immediately do the adjacent panel, it will leave a lot of paint and may cause a run. So, I often run the edges and then step back for a couple minutes before laying the main panel. You can see you have to plan the panel before you start your spray.

With non-metallic paint, like you are using, you can paint all panels laid flat, which will reduce runs. With metallic paint you should orient the panel the way it will sit on the car, so the metallic chips set the same way. Solid colors can be painted at any angle, so flat often makes sense...

sp53
07-02-2018, 11:06 AM
Well a couple of things jump out about my application of the paint. I am using a 1.2 tip and the sheet says to use between a 1.3 and 1.6—I do have a 1.4. I am also using about 25 to 29 psi into the gun after the trigger is pulled and 80 to the gun. I have the same set up as you with the 2 psi gauges. I will take your advice because there is something wrong with my technique. The paint work I put down looks more like hair follicles in skin; you know those little tiny holes where the hair comes out, so basically it is a dimple in the paint with a high spot. My temperature is 70 degrees and the sheet suggests, between coats 5 -10 minutes at 70 so I should be good there and I am out of the sun.

Next time I spray I will use the bigger tip and slow down the air flow. I have put the panels vertical because I felt I could get the paint gun perpendicular to the work better that way. However, my gut tells me something like the panels at a 45 would be the better of 2 worlds because I could see the edges better and not have to bend down as much for the longer panels. I enjoy this work but wish I would has started it at 25 not 65

Ah the base coat- clear coat sounds like the way to go. However, I will say I see these new cars like the Fiats around town and they have that solid enamel look like I was going for and liked. Deep down I knew I would never get this the first time. I have been a journeyman too long for that and built too many things. The Buddhistic principle of the experience having the real value is a truth for someone like me. It is odd however that I still take a set back with such personal impact. A collaborator once told me that the pain of failure and joy of success are the same thing; they are both perfectionism.
Peace out

CJD
07-02-2018, 11:19 AM
See...small tip and a bit high on the air pressure likely solves the problem. Just be ready, as you will have more paint laying down faster than you are used to once you set the tip and pressure. When right it will lay down with an orange peel at first, but the paint will be thick enough to flow out into itself within 5-10 seconds. So it will always lay with the orange peel, but the key is that it should be just wet enough to smooth out right after.

If you lay a stripe and then watch closely, you will see it flow out smooth. If it doesn't, you can make another quick pass immediately to give it a bit more volume to aid the flow. Also, if don't see if flow out...then you need to up the paint control and/or slow your speed across the panel.

When you get just the amount to get it to flow out...then do NOT be tempted to add more!! That's when you get the runs (no pun intended). I can't tell you how many times I had a dry spray...then upped the amount and resprayed, so it looked So much better!!...and then thought, if it worked once, lets add some more!?!...only to get a huge slow motion run!! Bummer. So, just enough to get it to flow, but not more than that until you wait your 10-15 minutes between coats.

Good lighting is really important...and I find more so as my eyes get worse. I used to be able to see a light spray on , say, an edge. Now days I have to study the tricky areas up close with coke-bottle lenses to make sure I didn't miss a spot. Getting old sucks...but it's better than the alternative?!?

You are almost to the point of bringing it all together, so don't think you can't have a great finish...look how far your bodywork came in a short time!!

Oh, a couple more things that may, may not help:

My personal "comfort speed" when spraying is about 1 foot every second. So if I start on a 3 foot door, I start the spray about 6 inches off the panel, once I hit the panel I could count thousand 1, thousand 2, thousand 3, and I am off the panel and stop the spray about 6 inches after. I pause for time to think about the next line, and then repeat in the opposite direction...spray, 1, 2, 3, past and release. This is just to give you a reference until you find your own comfort speed.

I usually start spraying too thin (since runs are worse in my mind than orange peel), so after the first pass, look at your line and see if it is flowing correctly. If it is I keep going. If not, I dial up the paint...re-run that pass faster (since it already has paint), and then re-check the flow. Run the next adjacent pass, study it, and so on...until you are happy the paint is going down just thick enough to flow, but no more.

You do have a decent "spread" between flow and run with most paints. And that is fortunate! Many times you can't help doubling a pass over an area, especially when some intricate body lines come together. The area around the rear bumpers comes to mind...you have to spray in a couple different directions to get everything, and therefore some of the passes end up over-lapping. I'd estimate the "spread" between flow and run is about half an average pass, if the flow and speed is right. So I double my arm speed over the intricate areas to allow for the overlap...and often lay a couple fast passes rather one normal. Hope that makes sense?!?

Anyway...enough for now...Good luck and Godspeed John Glenn!

sp53
07-18-2018, 10:45 PM
Cutting and buffing paint is still un-mastered by me anyway. The use of enamel probably was not my best choice either, but I never figured I would get the body as straight as I did. Anyway if you look at the picture of the hood you can see some stripes on the passenger side. One guy tells me I need to use cutting compound and another guy tells me to keep using 1200 paper and sand down and buff and sand down and buff, but the going is very very slow. My question is what and how do you cut. I mean everyone calls it cutting and buffing, so I am thinking on the other panels I should maybe try some of this cutting compound, but it sounds like I could do real damage at least I can see the possibilities of cutting through to primmer because I have will the paper. . Just looking for suggestions.

CJD
07-19-2018, 11:51 AM
When you hear “cut”, think “wet sand”. 1200 will not remove the dry areas very fast. About 5 minutes with 600-800 would equated to about 30 minutes sanding with 1200. Start slowly with 600-800 around the worst spots. Work up to the 1200 right before firing up the buffer.

PC
07-19-2018, 12:53 PM
"Cutting" is just common slang for using an aggressive compound. So there isn't "a" cutting compound. There are lots and lots and lots of them. And I'm sure many of them could be useful to you when used with the right buffer, pad and technique.

Everybody has their favorites. Which is why you may be getting conflicting recommendations.

I may be off base, but I'm getting the impression that you may be getting too much advice from too many people (myself include). Some of these folks may be giving you bad advice. Some may be giving you good advice for what they think you need but may or may not represent what you actually need. Some may be giving you good advice that may or may not play well in conjunction with the advice others are giving you.

My advice would be stand back and take a deep breath.

Then, when you come up with an idea of how you want to try to proceed, try it out on a very small area, what we call a "test spot," to see if it works. The test spot should be small, no bigger than about 1ft x 1ft. And you should not do any larger an area until you have the whole process, beginning to end, dialed in. After and only after you have a working and efficient process should you start replicating it on the rest of the car.



I take it the "stripes" are from sanding in long, straight lines? What paper (brand, product name, part#) did you use?

I apologize, the earlier post where you mentioned that started sanding with a soft sponge and then switched to no block didn't really sink in to my brain. Now that my brain is back on line I need to say that that's not the best technique. Your fingers are not flat. As you sand some areas with get higher pressure than others and cause the grit to dig in, making deeper scratches that are harder to buff out. Sometimes you can literally get ghost images of your hand showing up as holograms in your finish. The sanding blocks they make for this process are dense, stiff, closed cell foam.

Assuming the stripes are sanding scratch, some possible causes could be the aforementioned fingers, sanding with too coarse abrasives, sanding with common general purpose abrasives (as opposed to specifically engineered finishing abrasives), not progressing to fine enough abrasives, using an insufficiently aggressive compound, using a pad that's not well matched to the compound, using the wrong buffer speed, etc, etc...

PC
07-19-2018, 01:06 PM
Oh, and another tip,

When hand sanding, especially when doing your test spots, sand along only one direction with each grit.

Let's say you trying three grits, a, b and c. If you sand side to side with a, up and down with b and at a 45 degree angle with c, any residual scratch left over after buffing with tell you exactly which steps worked and which didn't.

And never hand sand in a circular motion. Circular scratch doesn't buff out cleanly.

TexasKnucklehead
07-19-2018, 01:40 PM
Since we've established that you're probably getting too much input and advice, I'll chime in too. -I have only painted one car, and only used base-coat/clear-coat but I had a very good coach living across the street. He made it clear to me that the difference between a $2,000 paint job and a $20,000 paint job is not the paint, prep or ability of the painter. It's the way the paint is finished -or- what he called 'color sanding'. I had tons of orange peel because I was unable to do at least one of the things mentioned by John. But I put enough paint down, that it could all be sanded flat and polished smooth. His approach was to wet sand with finer grit until a wet spot lost all shine,including the low spots (of the orange peel). Always use a small flexible sanding block and keep it wet. Keep changing out the water when it gets cloudy from constantly rinsing the paper. Keep checking for 'all dull' surface because you don't want to go farther than you have to. Tape off all corners, edges and do them last and very carefully. I 'color-sanded' areas less than a foot square at a time. Most people think I paid much more than $2,000 for my paint job -but it took time.

You are on track. It looks great.

PC
07-19-2018, 02:13 PM
All good advice.

But I do have to disagree with the idea that "the difference between a $2,000 paint job and a $20,000 paint job is not the paint, prep or ability of the painter. It's the way the paint is finished." I believe every step counts.

I've seen many defects that couldn't be fixed after the fact. For example, I see a lot of finishes where there are defects below the the base coat, usually from sanding primer or filler with too coarse paper or before the layer has set. If there's a problem below the base coat there's nothing you can do to the top coat to fix it.

TexasKnucklehead
07-19-2018, 03:01 PM
I believe every step counts.

I totally agree. I could have said that better. Each step is as important -no amount of color-sanding will take the warp out of a panel, or hide poor body work. But given a perfect body or perfect body work... that being said, a better painter would have had to spend much less time removing the orange peel that I had. But (I think) even the best painters know how to 'fix' their imperfections.

sp53
07-19-2018, 03:30 PM
Thanks for the encouragement you guys; I really appreciate it. The strips are from the paint gun; they have been there all the time. Maybe I moved my wrist or something or stepped back a few inches when spraying. I believe they are called dry strips or spots in the painting world, and often people put more paint right over them at first, but I was scared of running. The strips are way better than when I stated working them. The good news is I have 3 good even coats on the hood both back and front with no runs, except one very very tiny droplet one on the top edge that came right off. I almost think 4 coats might be better or possible, but I was afraid that could be too much and sage. The paint sheet said 3 coats or until covered, but does that mean stop at 2 if covered?

Is that your car behind the orange Tex-N? I like all the information I can get; I just need to synthesize it for my way of working. And please speak up. I must say John that is what my gut was telling me to do and I believe you sand something like that in the beginning, but I can only hear it when it is in front of me sometimes and I called the guy that painted my green tr3 and he basically said the same thing, but I do not like bothering him because he has a custom shop with employees and stuff. PC I hear you about the primmer imperfections and Tex-N I hear on the 2K to 20K it is so true.

I am just out in shop like a nervous cat not wanting to make mistakes, but again that is perhaps the main reason I wanted to learn this trade was so I would not feel intimated by it. My upper neck and back are very tight from sanding and buffing, and I am sure much of it is psychosomatic tension. Heck I have a 20 year cat with one tooth left and she comes out and looks at me like relax.

sp53
07-19-2018, 09:27 PM
Texasknucklehead I think I just figured out your pictures. It is your yellow car with orange peel, and then the white looking picture with the orange is your car ready for buffing after wet sanding the orange peel off for a week. Learning car painting is the lunatic fringe; I love it!!! It is the life force; well at least for old guys.

CJD
07-19-2018, 11:52 PM
Steve, I’ve told you many times that doing a spray is the most stressful thing I have ever done...and it never seems to get easier. I was never as stressed teaching newbies to fly T-38’s, and I’m convinced they were trying to kill me!

You are trying to control so many little things, so many of which are simply beyond our control unless you are fortunate enough to have access to a paint booth. Thankfully many small errors are repairable during the buffing stage. And if they are too big, then the layer of paint becomes an extra layer of primer, making the finished job even even straighter in the end.

I think you have all the pieces you need to do this. The confidence will come as you knock off each good panel!

PC
07-20-2018, 11:31 AM
Steve, two questions:

Do you have an air compressor? If so, how powerful?

Is the Finesse-It 39003 the only product you've been using with the buffer?



(OK, 's 2.5 questions...)

PC
07-20-2018, 11:35 AM
It would also help if you post pix of the 20 year cat with one tooth.

sp53
07-20-2018, 03:43 PM
Well the cat rarely shows her tooth, but I do have an air compressor. The finesse ll compound is a polish and I have that Black Ebony glazing I might try when I get the orange peel down enough and after I use the finesse ll. I guess there is new 3000 sound paper that kinda looks like a leather pad. I picked one a pad of it, but have just been using it by hand when I get buildup of paint from wet sanding. The 3000 stuff is supposed to provide a very high gloss, but I have not got the Velcro adapter for it yet plus I am not sure about using it. What I really want is the orange peel removed and a flat surface and some gloss.

sp53
07-20-2018, 07:23 PM
Tex-N, I am so glad you posted your orange peel photos because we are both doing our first paint jobs. I thought that clear coat base coat did not orange peel because I did not know any better. Anyways, I hope this not too confusing, but when you were doing the "color sanding" and got to those little tiny low spots maybe 1/16 in diameter between the orange peel-- did you leave any of them shinny so the buffer would remove paint and come down to them. Or did the whole panel become dull in every angle of light before you started buffing. I mean like twisting the panel and looking super close, so that the whole galaxy was dull at any angle. They to me look like little bright stars in a galaxy. I was in high school in the sixties, but anyways-- all gone –dull-- before you buffed

PC
07-21-2018, 01:09 AM
The reason I asked about the compressor is that pneumatic palm sanders are the workhorse of the refinishing world. If your compressor has the power to run one you may want to consider it. Everybody flinches when they first hear the idea of wet sanding with a power tool but the reality is that they are far more consistent than hand sanding and when used properly give far better results with way, way, way less work. They actually produce a less severe scratch than hand sanding.



... The finesse ll compound is a polish and I have that Black Ebony glazing I might try when I get the orange peel down enough and after I use the finesse ll. ….
Since 3M’s website is pretty useless, I called their tech support. They said Finesse-It II 39003 is a fine finishing polish. It will not remove sanding scratch. You will need to use a compound after sanding and before the 39003. (They also said 39003 is a discontinued product.)



…. I guess there is new 3000 sound paper that kinda looks like a leather pad. I picked one a pad of it, but have just been using it by hand when I get buildup of paint from wet sanding. The 3000 stuff is supposed to provide a very high gloss, ….
3000 paper does not provide high gloss. Nor does any other paper used in the auto finish industry.

What 3000 paper does is produce scratch that’s fine enough to remove easily with a compound. You will still need to compound.



… when you were doing the "color sanding" and got to those little tiny low spots maybe 1/16 in diameter between the orange peel-- did you leave any of them shinny so the buffer would remove paint and come down to them. ….
Buffing does not remove orange peel. Buffing makes the finish glossy. If you buff orange peel you get glossy orange peel.


The more or less “standard” process for sand, cut and buff is:

Coarse (“color”) sand to remove or reduce texture (orange peel) – abrasive sheets approximately P800 (ish)

Fine (“color”) sand to remove scratch leftover from coarse sanding – abrasive sheets, approximately P1200

Compound to remove sanding scratch leftover from fine sanding – heavy cutting compound, rotary buffer, wool pad

Polish to remove swirls and haze leftover from compounding – finishing polish, rotary or DA buffer, foam pad


That’s pretty much the "generic" (dare I say "universal?") process. Follow it and you maximize your chances of success.

It can be modified depending on the specifics of a given situation. Some may add extra fine sanding (P3000, P4000 or P5000) to reduce, modify or possibly eliminate one of the buffing steps. Some may use only foam pads, Some may use only DA buffers, etc. But just about everybody starts with the generic process and only makes changes as they develop a system to meet their specific needs.

sp53
07-21-2018, 09:44 AM
Thanks for typing that out PC; I followed every word of it and understood what each step means now plus I have it in print for reference. When I talk to someone, it often goes in one ear and out the other. My concentration is in question. Yesterday I was behind this new black Mercedes SUV and noticed the orange peel from 10 feet away on a beautiful vehicle. So I can see now this paint world is the lunatic fringe and the color sanding would be at my level the only way to get that high quality because of my inexperience and equipment I have. I might stop fine tuning this paint job if I can stop myself before the asylum, but time will tell. In my next incarnation perhaps I will come back as painter for Maaco auto painting and spray a couple of cars a day, so I get a feel for everything and become one with the paint gun and stop this orange peel madness. In my missed spent youth I played a lot of pool and knew some really great pool players who would shot with a broom stick as an equalizer when the situation arose. So maybe I could get so good I could lay down perfect paint with HD paint gun.
Peace out

PC
07-21-2018, 10:30 AM
.... Yesterday I was behind this new black Mercedes SUV and noticed the orange peel from 10 feet away on a beautiful vehicle. So I can see now this paint world is the lunatic fringe ...

Heh, heh. Wait till you start seeing buffer trails (a.k.a. swirls, holograms...) from a block away.... :jester:

Alfred E. Neuman
07-21-2018, 12:01 PM
Yesterday I was behind this new black Mercedes SUV and noticed the orange peel from 10 feet away on a beautiful vehicle.

Every Mercedes I've worked on that's newer than about 2010 has a level or orange peel that I would find unacceptable from any collision shop fender repair. I'm not sure if it's the way the clear is applied or a byproduct of the paint they're using.

CJD
07-21-2018, 03:59 PM
We just test drove Jaguars. They have a large amount of orange peel too. The Cadi’s we tested were factory buffed.

The circle has come round and the US cars have improved!

Alfred E. Neuman
07-21-2018, 05:18 PM
Without a doubt the best factory paint I've seen lately is on Japanese cars. We went and drove the Subaru BRZ and ND Miata last weekend. Both of those had flawless paint.

Miata FTW! Now I'm just waiting for the 2019 with 181hp to get here in the fall and it's MINE!

sp53
07-26-2018, 07:00 PM
So I am going to start using some 2000 and or 1500 wet sand paper, do I want to stand with a block in a straight line or do I want to use a block and sand in circular motions?

CJD
07-26-2018, 09:49 PM
I was taught to use circular motions, the idea being to minimize the depth of any scratches. If you go in one direction then the depth of scratches compounds. In circular motion you never repeat the same exact pattern, so the depth of scratches is minimized.

I also know the marine shops recommend straight sanding patterns, always the lengthwise direction of the boat.

Is that clear as mud?!? Using 1500 grit there won’t be many visible scratches however your sand it.

PC
07-27-2018, 03:12 AM
I was taught to never sand in circular motions. The scratch is harder to buff out.

With any finishing process consistency and uniformity are the biggest determining factors in quality. Circular hand motions are extremely inconsistent and produce the least uniform pattern.

I don't believe the theory that straight sanding would make the scratch deeper. Scratch depth is determined by the grit size of the abrasive. The first pass removes some material and leaves scratch. Subsequent passes will take down any high spots and the remaining scratch will be the same depth (but the total film thickness will be reduced).

Uniformity and consistency are why power sanders produce better results than hand sanding. It's impossible for a human to make identical motions thousands of times in a row. It's easy for the machine and it never gets tired. If you examine scratch closely you'll find that power sanding leaves scratch that's typically 500 points finer than from hand sanding with the exact same grit paper.

See my earlier post regarding sanding direction. https://www.britishcarforum.com/bcf/showthread.php?113565-Buffing-out-paint&p=1088663&viewfull=1#post1088663

CJD
07-27-2018, 09:05 AM
I don't believe you have more control with a machine than your hand. After all, your hand is controlling the machine. You can tell in an instant if a bit of dirt is under your paper using your hand. Not so with a machine...and as for direction, the buffer works in a circular motion, doesn't it? Wouldn't there be linear buffers if straight was better? Sorry, just what I was taught!


I am not saying to never sand straight, as many areas , like along the top of the doors or the trough on the sides of the bonnet, must be done with straight strokes. But in general a shine is a combination of many tiny microscopic scratches oriented in many different directions. On large flatish panels circular sanding and buffing produces the best shine from any viewing angle. If all the scratches align, then the finish will appear different from different angles.

PC
07-27-2018, 04:40 PM
I think we'll have to agree to disagree.


I don't believe you have more control with a machine than your hand. After all, your hand is controlling the machine. ….
With the DA you only need to control overall pressure (light) and placement. When hand sanding you need to control those plus direction, angle, pressure at each point in the arc, etc. And again, there is no way a human being can replicate exact motions thousands of time in a row.



…. You can tell in an instant if a bit of dirt is under your paper using your hand. Not so with a machine.......
If you work clean you won't get chunks big enough to feel, especially if you’re using a block. A human hand will never be able to feel a few 800 grit particles while sanding with 1200 paper. But you will be able to see the resulting deep scratches. That means going back and re-sanding or spending way too much time buffing.



...and as for direction, the buffer works in a circular motion, doesn't it? Wouldn't there be linear buffers if straight was better? ….
There are linear sanders. But the machine of choice for finish work is the dual action sander, which makes an orbital motion, not a circular motion. And since the machine is controlling the orbit, not human muscle, the scratch produced is extremely controlled and consistent.



…. But in general a shine is a combination of many tiny microscopic scratches oriented in many different directions. On large flatish panels circular sanding and buffing produces the best shine from any viewing angle. If all the scratches align, then the finish will appear different from different angles.
The best shine is produced by the reduction and elimination of microscopic scratches. When all the scratches are aligned a process that removes one will remove them all. Scratches that are randomly distributed will also be randomly removed and randomly left behind, making for more work buffing.

The point of multi step process is for each step to completely remove residual defects imparted by the previous step.



Luckily, nobody has to take my word for any of this. It's easy to try it for yourself, see how the results look to you, and decide what works for you.




Here's a guy showing the basics of using the DA (The sanding part comes at about 5:32 in.)



https://www.youtube.com/watch?v=nzWGaEkEf3A

CJD
07-27-2018, 08:28 PM
That’s a circular sander...am I missing something?? I thought the discussion was linear strokes vs circular.

Oh, just sitting here thinking. I forgot that I used a pneumatic sander just like in the utube vid on a Cadi back in ‘86. I watched a film and a shop was using those to crank out the pre-paint sanding, so I thought that was the “bomb” and bought one. Granted, I may have used it all wrong, but the finish came out horrible. The sander cut lows and highs in a finish that was straight before I started. It was the second worst finish I ever sprayed.

I chucked the sander. Since the dawn of time all the best finishes have been “hand rubbed”. You can do it faster, but not any better. The last bodywork I had done by a shop was a Jag about 2 years ago. I sent it back 4 times until they got it right! I wasted more time driving back and forth than if I sprayed the bumper myself in the end. Shops are interested in cranking a profit. They are not always the best source for “best” way...they are for “fastest”.

PC
07-28-2018, 03:05 AM
That’s a circular sander...am I missing something?? I thought the discussion was linear strokes vs circular.....
The machine is dual action sander. Its motion is orbital, not circular. But if you want to think of it as a compound combination of modified arcs, that’s reasonable.

The point I’m trying to make is comparing linear sanding by hand to circular sanding by hand to orbital sanding by machine.

It’s pretty easy to compare circular and linear hand sanding. You do patches with each and compare the results. Then buff each with the same buffer at the same speed using the same compound, pressure and time. Then compare the results again.

You can’t equate circular hand sanding to orbital machine sanding. It’s impossible for human hands to replicate the motion of a DA. But you can compare results. Circular hand sanding, even with fine papers, produces visually circular scratch that’s difficult to buff out. DA sanding with the same paper produces a uniform haze with no visible scratch lines that is easy to buff out.


...Oh, just sitting here thinking. I forgot that I used a pneumatic sander just like in the utube vid on a Cadi back in ‘86. I watched a film and a shop was using those to crank out the pre-paint sanding, so I thought that was the “bomb” and bought one. Granted, I may have used it all wrong, but the finish came out horrible. The sander cut lows and highs in a finish that was straight before I started. It was the second worst finish I ever sprayed.

I chucked the sander. ....
Could have been a lot of things. Thirty years after the fact it’s impossible to say what went wrong. but I believe that if you had gotten good advice and instruction you would have had a much different experience.


.... Since the dawn of time all the best finishes have been “hand rubbed”. You can do it faster, but not any better. ...
Like I said earlier, I’ll have to agree to disagree. I believe the opposite. I believe you can do it better and faster.

“Hand rubbed” was the thing back in the day when soft lacquers were common and high performance machine abrasives weren’t. Times have changed. Paints have changed. Abrasives have changed.


.... The last bodywork I had done by a shop was a Jag about 2 years ago. I sent it back 4 times until they got it right! I wasted more time driving back and forth than if I sprayed the bumper myself in the end. Shops are interested in cranking a profit. They are not always the best source for “best” way...they are for “fastest”.
Any tool can be misused. And it’s certainly common enough for these particular tools to be horribly misused by body shops that don’t care about quality and are only interested in minimizing costs. But that says nothing about the tool and everything about the user. And these tools aren’t used exclusively by bottom feeders.

Chip isn’t just a paid endorser. He uses these tools. As do other top tier custom builders and restoration shops.

Shops putting hundred thousand dollar paint jobs on million dollar show cars aren’t looking to cut corners.

CJD
07-28-2018, 09:08 AM
I think we both have different definitions of "difficult to buff out". I assure you I can beat any machine sanded surface by hand. You will beat me in the time it takes, though. Shops use power tools to save time and money...but the finish does not improve. A professional hand rubbed finish is as close to perfection as you can get...so how can you improve on that? 9 times out of 10 I can study a repaired surface and tell you if the shop used power tools to prep the final primer, and usually what type sander they used. That is because power tools are easy to control on large panels, but difficult on the corners and crevices. I read an entire book in the edges! On the 10th time I bet there was some hand sanding envolved to clean up the tool marks. Watch the Smithsonian show on the Bentley and Rolls finishes...they are still hand rubbing them. I think that pretty much says it all...when time and money are not a factor (like our hobby painting) Bentley still hand sands every car.

Last time I checked an "orbit" is circular. I still do not understand how a circular arc by a power tool is different than a circular arc by hand and block. Are you saying the size of the circles makes a difference? I look at it from the opposite perspective, in that it is not impossible for one's hand to duplicate the power tool, but rather the power tool can never entirely duplicate one's hand.

smaceng
07-28-2018, 10:00 AM
So I had never painted a car, but wanted to. I took a class at the local JC. I bought a TR6 that had been media blasted and primed. I decided on a two stage BRG. So I got the big compressor, proper filters and desecants. Added a house fan, filters and lots of lights to the garage. I first sealed the panels to avoid an interaction with the unknown primer sprayed by the media blaster. I then sprayed on a high build primer, sanded, and then another coat of sealer. This was followed by 3 coats of base and three coats of clear. I cut using 3m wet/dry paper starting with 1000 (wet) then 1500, 2000, 2500 and final 3000. After that I used the variable speed buffer (3M), with their system, first wool, and three pads of foam (black, white, and blue). I used Meguiars buffing compound 105, 205, and 7. It didn't turn out perfect, but I have gotten a number of comments that it looks like a professional spray. It is a lot of work, and I'm not sure I will do it again. Good luck, Cheers, Scott in CA54724

PC
07-29-2018, 12:52 PM
…Last time I checked an "orbit" is circular. I still do not understand how a circular arc by a power tool is different than a circular arc by hand and block. Are you saying the size of the circles makes a difference? I look at it from the opposite perspective, in that it is not impossible for one's hand to duplicate the power tool, but rather the power tool can never entirely duplicate one's hand.
Maybe I’m confusing things a little with the way I use the term “circular.” Being sort of OCD I think of textbook mathematical circles, very round things with a single, constant radius, or at least something very close to that.

Pointless side note: (sorry if this just adds confusion, but I can’t help myself) planetary orbits are elliptical. They have two radii. They are only circular in then special case where the radii are identical (which doesn’t happen in nature).

Anyway, the DA’s “orbit” is a spirograph pattern. If you consider the flowers generated by a spirograph to be circles, that’s OK. But whatever you call them, when you make them with sandpaper they aren’t just planform patterns. They’re 3D structures.

The whole point is consistency. A uniform structure can be removed with a uniform process. If the structure is uneven the removal process will need to cover a greater range of structures. With a buffing process, having to cover a wider range of structures means more work and more opportunities to miss deeper defects. You get a cycle of work, inspection and re-work with more instances of residual defects.

A human hand can’t replicate its own motion from one movement to the next, let alone thousands in a row. The resulting scratch pattern is far less consistent than produced by the machine.

One of the worst side effects of circular hand sanding is that the scratch left by subsequent sanding steps looks the same as the previous steps’ that were supposed to be removed. You can’t really tell if you’ve successfully removed the defects from earlier sanding steps until you start buffing and find the scratches aren’t coming out as fast as you expect (or at all).

With linear hand sanding in alternating directions you can see when you’ve removed the previous steps’ defects. Machine sanding produces a pattern that is so consistent that you can also see if the previous steps were removed. But most importantly, due to the uniformity of pressure throughout the entire arc, machine sanding produces a shallower structure that’s easier to remove.


I think we both have different definitions of "difficult to buff out". I assure you I can beat any machine sanded surface by hand. You will beat me in the time it takes, ...
I obviously think otherwise. But since there’s no way to put it to the test though our keyboards we’ll just have to continue to disagree.


... A professional hand rubbed finish is as close to perfection as you can get...
I’d say this is the core of our disagreement. Unless we meet in a garage somewhere and play with it all on paint with our own hands (and machines ;-) ) we will continue to disagree.


.... Watch the Smithsonian show on the Bentley and Rolls finishes...they are still hand rubbing them. I think that pretty much says it all...when time and money are not a factor (like our hobby painting) Bentley still hand sands every car….


Bentley factory. Primer sanding at 1:25.


https://www.youtube.com/watch?v=Aw2uMpSd1wg

Bentley factory. Finish sanding at 16:56


https://www.youtube.com/watch?v=kzZwjpn-Qbk

PC
07-29-2018, 01:00 PM
Rolls Royce factory. Finish sanding at 0:24


https://www.youtube.com/watch?v=QiQwRqDcmdQ


Rolls Royce factory. Finish sanding at 17:25 – 18:58


https://www.youtube.com/watch?v=bdqQhBTqHgo

PAUL161
07-29-2018, 01:51 PM
I saw a video the RR and Bentley being built a couple times and the craftsmanship is very impressing. That's what you pay for, not me, but someone! :encouragement:

CJD
07-29-2018, 07:55 PM
Uncle PC. I had no idea a discussion of linear vs circular sanding patterns would turn into ellipse, and Spirograph, and whatever. I can’t keep up...you win!!

But, a parting thought...what shape orbit does a geosynchronous satellite have? And...would that still be considered an orbit?? So...is an orbital sander truly “orbital” in pattern???

That oughta get your OCD crankin’!

PC
07-30-2018, 03:08 PM
I’d say we both win. The fact that we can throw opposing ideas back and forth on a subject we both have very strong opinions about, while keeping it friendly, shows what a great forum this is. How often does that happen on the internet?


A geosynchronous satellite has an elliptical orbit. All objects whirling about in space, held by gravity, move in elliptical arcs.

Here’s the part where my OCD caused confusion. A circle is just a special kind of ellipse. All circles are ellipses. But not all ellipses are circles.

Most people think of an ellipse as a squashed circle. But mathematically, a circle is an ellipse whose wide part has been squished until it’s exactly the same as its narrow part. The eccentricity of an ellipse is how squashed it is. Zero eccentricity would be a circle.

The orbits of geostationary satellites are as close to zero eccentricity, perfectly round circles as we can make them. That way they don’t appear to move when we look up at them.

https://cseligman.com/text/history/samesizeellipse.jpg

You can also have geosynchronous satellite orbits that aren’t round, tracing out more pronounced ellipses. In that case they would appear to move in and out, back and forth when we look at them. But they would always occupy the same patch of the sky.

So is the circular orbit still an orbit? Definitely. But keep in mind that the word orbit has different meanings in different fields of study. There are always textbook definitions in each field of study that are more specific than the way words are used in common language.

And I have to apologize for saying circular planetary orbits don’t occur in nature. That was overly picky. It would be more accurate to say that the orbits of the planets in our solar system are ellipses, not circles. The orbits of our local planets are only a little squashed. Some, like Venus’ and Neptune’s are pretty darn close to circles. Comets’ orbits, on the other hand, are super duper squashed.


And just to confuse things even more, back to the DA sander…. With more math! (Yeah, you got my OCD crankin’.)

We said that mathematically, circles are special ellipses. Well, ellipses are special versions of yet a larger group of shapes called trochoids.

So, all circles are ellipses. And all ellipses (and therefore circles too) are trochoids. And then there are whole boatload of trochoids that aren’t ellipses or circles.

The DA sander produces an “orbit” that’s trochoidal. It’s sort of a distant cousin of a satellite’s orbit.

Here’s a pic of a trochoid that’s like the motion of a DA sander.


https://www.math.hmc.edu/~gu/curves_and_surfaces/curves/epitrochoid.gif


And for all you Zoom Zoom fans, the housing of a Wankel motor is yet another kind of trochoid.

https://www.pattakon.com/PatWankel/PatWankel_iGR_10.gif

DavidApp
07-30-2018, 08:38 PM
It is great to follow this discussion that is being conducted in such a courteous manner. It is a testament to the forum.

I have been following it to get painting tips but I feel it is going a bit further than I plan to go. I have learned a lot along the way.

David