Toning with conversion varnish

      Adding tonal depth without building up too much finish. August 13, 2002

Q.
I use SW CV with catalyzed vinyl sealer or self-seal. Sometimes I will tone using SW wiping stains in thinned sealer, then glaze. Is this right? How can I tone, maybe a couple of times, without having a lot of buildup of finish?

Forum Responses
From contributor M:
I usually seal, glaze, shoot a thin clear coat and then use a toner to get the final color. I use Unical 866 tints mixed with thinner and CV at a ratio of about 5 parts thinner to one part CV.



Homestead Finishing's transtint dyes appear to work well with CV.


Watch it toning with SW wiping stains. There are chemicals in the stain that you do not want mixed with the sealer. Use pure dyes (any brand is fine) and/or pure pigments - 844 or 866 series - for tinting CV or sealers. By doing it this way you will get a cleaner look. Toners can be used before or after your glazing steps. Where and how you use a toner depends on what type of color you want to get. Just remember that dyes will keep your system more clear, while pigmented toners will muddy the look.

Bob Niemeyer, forum technical advisor



From the original questioner:
Bob, you mention putting dyes in the CV. Which type? I know nothing about dyes. Also, one way I have been toning is to thin SW wiping stain down with VM&P Naptha and lightly coloring the piece, then spraying the finish coat after it dries. The problem is I can't tell what the real color is because it flashes off so fast until it's finish coated. The SW rep said this would work. Do you see problems here?

Contributor M, in your response you mention thinning the CV considerably, even 5-thinner / 1-CV. I have been afraid to do this, fearing that I would somehow ruin the product integrity. Is there a problem with thinning CV a lot?

What is the very best way to tone when using CV as a topcoat? What product is the best and what proportion solvent should be used? Should a catalyzed vinyl sealer be used, or is self-seal with CV the best?



From contributor M:
I haven't had any problem with thinning the CV that much. I put a full topcoat over it anyway.


As far as thinning conversion varnish and possibly ruining the integrity of the film, it depends from manufacturer to manufacturer if this is okay. Akzo Nobel does not like to see their product thinned too much, for this very reason. You will have to ask the tech support staff or the chemists/formulators (Sherwin-Williams, in your case) about this issue.

I would think that you'd want to get all your coloring done and then only apply your clear topcoat finish on top. That means that you ought to make good use of your vinyl sealer with either metalized dyes or proper paste colorants (pigmented dispersions) to make your color. You can thin the sealer way down to minimize film build.



From contributor R:
I use vinyl sealer until all glaze coats are completed, locking in the last one. If you need to only tone or shade, CV will work. You can mix the color into a full coat if you are doing an overall toning of the piece. If you are doing color correction or artsy shading, I find thinning works better and I would prefer doing it in the vinyl sealer coats. I have seen people have bad adhesion problems putting a glaze coat between coats of CV.


From contributor B:
Contributor R, I have always done the sealing of glazes with the vinyl sealer as well. Everybody questioned why I did that. I never had problems, so why change? It was said that glazes were formulated to be used with a direct application of CV or post cat and no vinyl sand sealing was necessary. Do you catalyze the vinyl sealer if you use CV or post cat? Or do you seal with regular vinyl sealer, scuff sand, then topcoat with CV or post cat?


From contributor R:
I don't catalyze my vinyl sealer. I did when I used SW because it didn't sand that well.


From the original questioner:
Contributor B, using SW CV, you didn't used to have to catalyze the vinyl sealer - they said you "could" catalyze it. This is the way I did it for several years. However, SW changed the specs and now say "must" be catalyzed under a catalyzed topcoat. I believe the reason for this is the critical time factor. I discovered this on the last project I did (the one I was toning). I used un-catalyzed sealer, saying to myself "I've done it for years, why not, it's just a small project." The problem was that on the last coat of CV, it wrinkled the finish. I had to strip the doors I was working on and start over. I am catalyzing the vinyl sealer from now on.


Makes you mad, huh? Same thing happened to me. No matter what the can says, you need to catalyze the sealer if used with the catalyzed SW CV.


From contributor C:
Toning with CV can lead to adhesion problems if it is thinned too much, as you need to have a certain volume of solids and other components for effective crosslink. One to one is all you should go, and that can still cause precipitation. Make your toner weaker, instead of trying to dilute it with thinner. Using the CV closer to the recommended viscosity will also let it stay wet longer, enabling you to see the true color, rather than having to guess when it flashes off too fast. Also, don't catalyze more than you will use right away, in case you need more for a later job down the road.

To the original questioner: your lifting problem was caused by laying your coats on too heavy and not giving enough dry time between coats, which allowed the solvents from your last coat to penetrate through your previous CV coats, which it wouldn't have been able to do if the previous coat had set up properly. That's what is known as a recoat window.



From the original questioner:
Contributor C, what do you tone with and how do you do it?

As far as the lifting problem, it had dried overnight. Shouldn't that have been long enough? I ended up topcoating with two coats of CV. I put one on before I went home. It looked fine the next day. I wanted one more coat on and that was the problem one, even though it had all night to cure. If you catalyze the vinyl sealer, would you still have the same recoat window problem?



Yes, it would have whether you catalyzed or not. The recoat window for most catalyzed coatings is after 8 hours and before 48. This is the critical time between when the finish on the object has started to crosslink and when the crosslinking is completed. What actually happens is that the film is wrinkled because the thinner in the newly sprayed coat cannot dissolve the previous coat completely, but yet the chemical resistance of the film is not sufficient to completely prevent the chemical attack of the thinner. This is what causes the wrinkling. It's a partial dissolution of the previous film. The best way to beat this rap is to get all of the coats down within 8 hours. That way each coat completely melts into the previous.


From contributor C:
To the original questioner: I tone with a stain that I make myself, without commercial bases that can cause trouble. Your best bet is to use dyes, like MLC dyes, mixed in your un-catalyzed CV, using a test panel to establish the desired effect. You don't need to catalyze the CV to do the test, but don't forget to add cat when you tone your project! When you sprayed your last coat the night before, if you had waited till it was dry enough to scuff sand, and sanded it that night, the next day it would have been hard enough to take that last coat without reacting.

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