Should I Use a Tinted Undercoat?

      A finisher who's having trouble hiding color variations in a Poplar project gets suggestions for tinting the undercoat. August 12, 2014

Question (WOODWEB Member)

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When running pigmented finishes in colors other than black and white, do you recommend tinting the undercoat/primer towards the final color? We have a job in-house in poplar with strong variation in wood color - from grey/green to white-ish.

On the project sample we ran the following schedule :
- Thin white catalyzed primer
- Sand 240
- White catalyzed primer
- Sand 320
(At this point the wood was uniformly white).
- Pigmented topcoat
- Scotch-Brite/sponge scuff
- Pigmented topcoat

The topcoat is Valspar Valtech Ultra pre-cat. We generally hit about 4 mils wet. The issue is that the final color (to me) is running a little lighter than the reference sample and I'm wondering if the white undercoat is telegraphing and washing the color a bit. Should I tint the primer coats towards the topcoats?

Forum Responses
(Finishing Forum)
From contributor M:
What color is the final coat?

From the original questioner

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The purple color.

From contributor R:
With 4 wet mils you should have complete coverage. Are you sure the color in the can matches the sample? We do tint our primer for brighter colors. Sometimes with bright colors like your purple they tint a clear finish and as a result don't get the normal coverage. I am not sure of the max dry film on your product so additional coats may not be an option, in that case tinting the primer would be the way to go. You could make a test sample with stripes of black and white primer and see just what kind of coverage you're getting.

From contributor M:
Purple/red/blue are sometime hard to cover with so I would suggest to tint your primer just to be on the safe side.

From the original questioner

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I'm as sure as I can be. The reference sample was a dip check (never heard of that) from the same can. Looks like a white postcard that has been dipped in the lacquer. Five mils total dry film is recommended, and we're right in that range (theoretically). The color is mixed in a white base. I like the idea of using different bands of primer.

From contributor N:
Some colors definitely hide better with a colored primer and surprisingly not just a primer tinted to the same color - with reds and pinks going grey is the way to go. Lighter grey for pastels and of course dark grey for deep reds. For your purple/pink I'd try a medium grey. Tint a small amount of primer with the appropriate black pigment (I don't know if UTC's will work with Valspar's Ultra). Starting lighter and working darker shoot some test pieces with the primer and finish until you find out dark you need to go for the right background color.

From contributor F:
If it's a darker color tinted primer will definitely help. I did a greenish color several years back that used a forest green tint that was much darker than the topcoat itself. I didn't understand why it had to be darker, but my finish guy recommended it and the color came out right on the money!

From contributor R:
We see reflected light. White reflects the most light (both wavelengths and intensity) while black reflects the least. Having an undercoat (primer) of a darker color creates less interference with the topcoat and, therefore, affects the hue and color of the topcoat. The topcoat can be tweaked even more by using a primer color that will adjust the final light more subtly.

I have used a lot of walnut and the colors of unfinished material are all over the place. So, one thing I do is use dilute dyes to shade the wood of different colors to get in the same ballpark so stains and finishes are more predictable. There was one batch for a fireplace surround and cabinets that would look very green under stains and finish. A little dilute red dye stain sprayed on the offending pieces before staining brought everything into the same color range.

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