Is It Worth Clear Coating over Opaque Finishes?

      Applying a clear topcoat over a pigmented conversion varnish has advantages and drawbacks. November 15, 2011

I have always primed with a conversion primer, then sanded and topped with a conversion paint (pigmented conversion varnish). I know some people will take the extra step of sanding the paint, then clear coating over it. What are the advantages of this? I am trying to decide if it is worth the extra time and money.

Forum Responses
(Finishing Forum)
From contributor C:
A clear coat will help protect the color, like they do on cars now. I would do it. The only thing to watch for would be your mil thickness. It is easier to fix clear than color.

From contributor P:
A clear coat that's not totally clear will shift the color a bit. A clear coat that yellows over time will do the same thing. Can be very noticeable on white finishes.

A clearcoat helps protect against coining, the dark discoloration you can get by dragging a coin or other metal object across the finish. That said, I only do it when there's a glaze.

From contributor R:
I've given it up, except when there is a glaze. You know what sucks? Having this beautiful paint job and then going to clear coat it and you find a piece of blue fuzz from your shirt, a hair, etc. - stuff that you'd never see in a stain or just a paint, but when you clear coat over, it's like taking a paint job and then putting a magnifying glass x10 over it. I got tired of dealing with that on every 1 out of 25 doors.

From contributor L:
I gave it up too. Extra work that is likely not getting paid for. I have been told time and time again by my rep that it is mostly a wasted step to do the clear coat on a paint job that isn't getting a premium dollar amount. After a while, I agreed. It does work though. If you will be compensated for it, do it. Eliminates the coining and makes touch up a bit easier.

From contributor M:
Used to do this, but stopped. Like contributor P said, it can discolor your paint or cause yellowing that may not have happened otherwise. I figure if the clear coat gets abused, you still have to fix that, so what's the difference? Plus it adds expense and another chance for a finish problem to occur. Since we do operable louver shutters we find the extra thickness created by additional finish coats can cause problems with our tolerances, but probably does not matter with cabinetry.

From contributor S:
I have not done this yet, but was wondering if I should to help with coining and such. After getting done with a pigment job and everything coming out perfect, it's hard to weigh the risk of then shooting a clear over a perfect pigment job. Shooting a perfect pigment job is 50/50, so why risk the extra step? A 100% flawless pigment job on a high end custom is a work of art by itself.

From contributor J:
I have my primer tinted, then spray clear conversion varnish over the primer. No extra work. 2 coats primer, 1 coat clear.

From contributor S:
I would have to prime 3-4 times. 4 times most likely. When sanding the second coat, you don't have light spots where you can see through the primer?

From contributor J:
I prime, fill any voids/marks/pin holes, sand, prime, sand, clear. I use Valspar post cat primer, and Valspar Ultraguard conversion varnish.

From the original questioner:
I talked to my sales rep a few years ago about clearing over primer, and he advised against it. He said primers don't hold their color like pigmented topcoats do. He said the primers will yellow in time. This was an ML Campbell rep, so I can't speak for Valspar, but you might want to look into it, if you haven't already.

From contributor L:
Primer colors are not blended for color match and can vary from can to can. You can box them to get a consistent color for one job but you can't guarantee the next will be the same color. I use MLC products and the rep has never said anything about yellowing of the primer.

I know a few finishers that use this technique and have never seen a problem with it. The colors are not as full as when you use a true pigmented paint.

From contributor JC:
I used to use MLC, and you're correct. They are not controlled for tint strength. The Valspar primer I use is non-yellowing and is considered tint strength. A lot of the MLC products still contain nitrocellulose. Even Krystal, which they say is non-yellowing, contains a small amount of nitrocellulose and will shift color over time (mind you it will be very little and probably not even noticeable).

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