Wet sanding question

[Drunken Goat]

So I am building a 62 bel air and painted it using model masters lacquer paint and gloss. I have 2 color coats and 5 coats of clear on the body. How long should I wait before wet sanding the clear?

Ps I search but couldn't find my question unless I missed it.

Thanks Gary

[Fat Brian]

A good rule of thumb is to wait until you can't smell the paint anymore. Some people use a modified food dehydrator or a curing booth made with an incandescent light bulb to speed this process up.

[StevenGuthmiller]

When I was using Testors Lacquer clear, I would usually wait about a week. But I would say a minimum of about three days. The "smell" test would be a good barometer. One thing I found out about Testors clear lacquers is the curing time is much longer than say Duplicolor clear. I had problems with the top coats of clear cracking over time occasionally. That's why I stopped using it. I would paint & then use at least three coats of clear, polish it out after a week or so, & everything would look fine. Then about a week or two later, I would start to notice a few fine cracks, & it would continue to get worse over time. You would have thought after 3-4 weeks everything would be dry & cured, but that's when the cracking would start to really show up. Mind you, it didn't happen on every paint job, but enough to make me stop using it. Now I use pretty much nothing but Duplicolor clear.

Steve

[fseva]

So I am building a 62 bel air and painted it using model masters lacquer paint and gloss. I have 2 color coats and 5 coats of clear on the body. How long should I wait before wet sanding the clear?

Did you apply all 5 coats in one session? If so, I think you should give it overnight and check it for softness in an area where you won't notice if you leave a fingerprint...

[fseva]

Some people use a modified food dehydrator or a curing booth made with an incandescent light bulb to speed this process up.

I'm one of those "some people"... I love my food dehydrator, and use it with all of my hobby projects - I make this distinction because I had found that when using real automotive lacquers or enamels, they were apparently not made to respond well to confined warmth - the top dries almost instantly, but leaves a barrier for the layers underneath so that they never really do cure!

[ZTony8]

Lacquers dry from the bottom layer out through solvent evaporation.That's why if you put another coat on top lacquer before it's dry the solvents are trapped and can't evaporate,leading to cracking.

[StevenGuthmiller]

Lacquers dry from the bottom layer out through solvent evaporation.That's why if you put another coat on top lacquer before it's dry the solvents are trapped and can't evaporate,leading to cracking.

That's what I had assumed was going on with the Testors clear lacquers that I had used. I've never had that same problem with Duplicolor clear leading me to believe that the Testors cures much more slowly. & even with the Testors, I had only had it happen a few times.

Steve

[Drunken Goat]

Thanks for the help everyone. I would wait a few hours between the coats of paint and clear.

[StevenGuthmiller]

Thanks for the help everyone. I would wait a few hours between the coats of paint and clear.

I usually waited at least 24 hours between coats & it still happened. Hopefully you'll not have this problem. I've never heard anyone else discussing it, so it must have not been a problem for most.

Steve

[ZTony8]

Quite often there will be recoat window information on the spray can label.Follow the guidelines.If there isn't any recoat window information then it's usually safe to recoat at any time.

[StevenGuthmiller]

The instructions on the Testors "Ultra Gloss Clear" say it can be re-coated after 2 hours. Other Testors clears say anytime. I never re-coated that soon. I always let it gas out for about 24 hours between coats & I still had the cracking problem, usually much later. Now that I'm using Duplicolor clear, I usually get 3-4 coats on all in one day, allowing about an hour of drying time between coats. No issues with the Duplicolor, other than an occasional paint compatibility issue.

Steve

[Lunajammer]

The way I've understood it Steve, is to either recoat within two hours while the surface is still soft, or after 48 when the surface is cured enough to let another coat grab hold. Anything in between (24 hrs.) is neither soft enough to blend into the bottom coat, or hard enough to accept another coat. I've never tested it to see what kind of trouble can occur, just took the advice that it should be avoided. But that's probably old school (old paints) advice too.

Edited March 26, 2015 by Lunajammer

[StevenGuthmiller]

I don't know either Mike, but if the Testors clears are that finicky, there should be some sort of "heads up" on the instructions other than "After 2 hours", or "anytime". There's a lot of gray area there.

Steve