You know me, always doing some goofy test or something. :D The subject of flow coats and how many coats of clear often comes up. A while ago someone asked if their clear would fill some imperfection. I forget what the exact thread was about but it got me to thinking, clear has as much or nearly as much "solids" as urethane primer, so I'll do a little test to show how much todays low VOC/high solids clears can actually "fill".

I took this piece of metal and made a few dents. I then filled those areas with filler and sanded one half of each spot with 120, the other half of each spot with 80 grit paper. I then cleared one half of the panel with two coats and one half with four coats.

So what I have is four coats of clear over 120 and 80 grit sand paper scratches and then two coats over the same. I mil checked everything prior to clearing to see what I had and then checked it later after clear, the two coat side gave me 3 mils and the four coat side gave me 6 mils. Now, we have to give a little one way or the other a half mil maybe more being this is a cheapy mil guage but these are the numbers one would expect.

The filler was seriously buried under that four coats I'll tell you that! It looked like a sheet of glass over the top of it, burying those scratches big time. On the two coat side you could see a little dryness, I can't say could could see the scratches because that 3 mils filled them, but there was a little that you could kinda see.

I took 1500 wet to it and cut it aggressively. No checking to see when I just cut it flat, I sanded the hell out of it and cleaned it up to see all the scratches gone completely. I polished it to a shine and mil checked it to find I had cut a about a mil off, maybe a little more.

So here it I have 80 grit scratches totally buried under clear with 2 or so mils (the absolute minimum you would want) on the two coat side and a full four mils on the four coat side!

This clear acted just as primer in filling these deep scratches. Hell, we don't even ask the primer to do that around the shop. NO filler would EVER be primed over with anything more coarser 180 scratches.

The point of this is, clear adds a lot of film build. A few coats is plenty to cut and buff and adding a bunch is SERIOUSLY adding to film build.

This is not to say that a "flow coat" is bad, but just be aware you are adding quite a bit of film thickness with every coat of clear, that is all I am saying.

Makes you go hmmmmmmm, don't it?

Brian

http://i200.photobucket.com/albums/aa167/BasicsofBasics/IMG_0888.jpg

Makes you go hmmmmmmm, don't it?



It sure does! And fwiw I'm always interested in your goofy experiments! I've learned quite a bit, Professor! Thanks for taking the time to do what you do for TC :thumbsup:

I want to see what it looks like after a month out in the hot summer sun.....

Brian,

That's good to know, thanks.

Question please: I will be shooting PPG "Shopline" base (color) on my '70. Can I use any brand clear over that "Shopline"? Or should I use the "Shopline" clear as well? If not, which clear would you suggest?

Thanks for sharing that Brian.

I want to see what it looks like after a month out in the hot summer sun.....

What is your point? Maybe you misunderstand what the test is all about. I would assume it will act exactly as any paint job will. For that matter, it will shrink way less because there isn't a bunch of solvent filled paint and primer under it!

Brian

Brian,

That's good to know, thanks.

Question please: I will be shooting PPG "Shopline" base (color) on my '70. Can I use any brand clear over that "Shopline"? Or should I use the "Shopline" clear as well? If not, which clear would you suggest?

Realistically you can use any clear over it. I am one to like to stick with the same brand. But honestly, it isn't a big deal switching clears.

Brian

DISCLAIMER!

This project is not to show "how much you can get away with"!! It is not saying you can use clear as a primer!

YES everyone, you WILL SEE your flaws thru the clear!!! If you fill scratches like I did here, you WILL SEE THEM thru the clear. YES you can bury them, like those funky tables with the coins and crap buried under clear resin at the pizza parlor, you can't feel these scratches, but you can SEE them!

All this test is to provide is a visual proof of how thick clear can get, that is all it is to provide, end of discussion.

YES, you can apply four coats of clear, cut it and buff it, no big deal. It will not fail, it is fine, with most clears.

This is just an example of exactly what is "happening" when you do apply that much.

Brian

OK, dude, chill out.

OK, dude, chill out.

Dave, I meant no harm in my responses. It is more about a number of responses to this I got on another site I posted it on. I am not saying anyone is wrong for what they thought was the objective, I didn't make it clear enough (if you will pardon the pun).

Brian

Thanks for the info. I think what this experiment does show is the possibility of maybe aplying added clear coats to a panel , then cut and buff to reduce/eliminate some wave if it shows up down the road.

It's all good. :thumbsup: I appreciate the time you take to write the books you do ( :) ) to help out the guys who try to do it themselves.
There becomes a point where you can have too much clear, but after seeing some GM white pearl colored cars, and some Mercedes cars that have 15+ mils of paint on them from the factory, the average restorer who strips a car can't get too much material on. The problems begin when what is under the paint is not up to snuff. :thumbsup:

Dave, then there is the other side, we have a 2007 Chevy pickup in here right now that you can SEE THRU the paint! It's black, and you can see the gray primer right thru it in bloches all over, very sad.

Brian

Brian, that is quite common, actually. I work in a GM dealership, so I see it all the time. Worst part is, when you try to match the paint, you first have to match the undercoat! No wonder why some colors have 7 or 9 alternates :noway: