Waterborne Bleed-Through Problem

      Advice on using prime coats and shellac to address bleed-through of grain with waterborne finishes. December 9, 2010

We are currently using Mohawk waterborne pre-cat lacquer and tinted sealer. The wood grain is bleeding through the finish. Our process is one coat of white Mohawk primer, then two coats of Mohawk tinted primer, then the topcoat of Mohawk waterborne pre-cat lacquer. The initial primer is not sealing the wood. It seems to soak it in and the wood grain bleeds through. When we scuff the first process and go over the top of the other finishes again, it does finally take. While this is a solid color and a lot of additional work, this laborious process will not work for stain. There has to be an easier way.

Forum Responses
(Finishing Forum)
From contributor J:
Do you mean your primer is raising the grain? I don't know that primer. I tried their sanding sealer and it was good enough. Have you followed the TDS (especially the wet thickness)?

From the original questioner:
We have already addressed the raised grain issue with success. The problem is that we have bleed through or see the wood grain through three coats of sealer and a coat of primer.

From contributor J:
Have you mixed the max amount of pigment?

From contributor R:
What species of wood are you working with?

From contributor E:
It sounds as if you need a white primer fortified with a tannin block.

From contributor O:
Some tannin stains can be rough with typical waterborne finishes. Try MLC Agualente water borne stain blocking primer. Blocks tannins very well. I typically spray two good coats and it dries fast and powder sands great.

From the original questioner:
We are using maple. I believe the tannin blocker could be a solution.

From contributor E:
I have had the same problem with Target tinted 6000. I solved it by using a coat of 2lb cut of shellac to seal the wood before the white. Works perfectly.

From contributor K:
We use Aqua-Lock for our white primer. Works great. I am also starting to experiment with the Renner primer that claims to block tannins.

From contributor R:
What's the consensus on Bin primer for waterbased coatings? Seems to dry pretty fast, sands easy, and blocks out tannins.

From contributor D:
The Bin works fine many times, but it seems like colors that take a heavy amount of pigments like dark browns and reds have given me more than my share of problems with cratering. Don't know how or why it happens, but it does.

What has worked best for me is to let the first coat of primer cure for a day before spraying a second coat. That usually does a pretty good job of locking in the tannins and results in a good finish. If I try to spray both primer coats and the topcoat in a day I will still get some bleed through on the final coat once in a while.

From contributor Z:
Try MLC Agualente primer. It is the best we could find and we use it all the time. Once you get the hang of it there is no need for shellac. We use a lot of box fans to speed dry it (don't need heat) and that also helps a lot with grain raise on MDF. Sands great.

From contributor M:
Contributor D's response seems to be right on with what the Zinsser rep told me - wait for a day to let the primer set before attempting to coat over it. Shellac is usually a great stain blocker, just not for exterior work, except for spot primer (for knots and sap).

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