Washcoat Tips and Tricks

Washcoat application can be a tricky process. Here, seasoned pros help a beginner get the hang of it. March 29, 2006

I must be the worst finisher around. I have tried and tried to get the wash coat method to work and all I end up with is wood that won't take stain. I have been using MLC vinyl sealer, thinned 4 parts thinner to 1 part sealer, and it still won't let the stain take at all. I've been spraying a full wet coat of MLC cinnamon stain, letting it sit for 1 minute, 5 minutes, up to 20 minutes and then wiping. Looks all the same - it all comes off. It seems I have better luck just lightly misting several dry coats of stain on and not wiping. The problem is it seems to cover up the grain a bit. Is there anything wrong with the misting method that I'm using?

Forum Responses
(Finishing Forum)
From contributor R:
Take three deep breaths. Scuff sand the washcoat with a 320 grit paper before you wipe the stain. This removes the majority of the film from the surface and only leaves it in the pores that are causing the blotches. The stain will still come out a little lighter, but not as bad as when you don't sand.

From the original questioner:
I should have stated that I do sand the wash coats. The sample boards used, 6, were sprayed, let dry, and then sanded with 150 on a Dynabrade and still no stain would take.

From contributor B:
I went to a ML seminar and I think their wash coat was thinner, like 8 to 10 to one. At the class we made a piece of white birch look like red mahogany. Not really my thing, but I know it is possible. I would call Louis and Company, their Portland branch, and ask to talk to Bernie.

From contributor D:

You say you are using 4 parts thinner to 1 part sealer. That's a good ratio if your sealer is 20% solids by volume. If it's more than that, say 25% solids by volume, then you need to increase your thinner amounts. You only want about 3-5% washcoat. Try doubling your mix, 8 parts thinner to 1 part sealer, and see what you get. If it starts to blotch, then slowly decrease your thinner amounts until you come up with the perfect recipe. Different woods will take wash coats differently. Alder will suck it right up, where maple won't take as much and it will lay on top of the wood. Sample boards, sample boards, sample boards. Practice makes perfect.

From the original questioner:
Solids by volume for the sealer in question is 13 to 17 percent. I wish I could post a picture, but I can't. When I apply the stain, let sit for a while, then wipe off, it all comes off. It's like staining a piece of glass. That's why I've resorted to the misting with the dry coats. Not loving it, but I don't know what else to do.

From contributor W:
Brush or spray the B10 clear stain base on the raw wood. Wipe it down. Let it dry completely. Scotch brite it (maroon). Then apply your stain by spray or brush. Wipe off evenly. If still too light for you, although it shouldn't be, spray mist your stain on top of the wiped stain. Don't overdo it. Just turn down your flow to where it's just covering what you want. Let dry, seal. Sand with 320. If still too light or uneven, make up toner with the stain and even everything out to match your sample.

From contributor J:
That is the way I do maple, but without the Scotchbrite step. Why do you do this step?

From the original questioner:
The stain base sounds like a good idea. I have a gallon of it that I will try. Never thought of that. I guess the clear stain base doesn't seal the wood quite as much?

From contributor W:
The reason is to break up any film on top that may interfere with consistent stain penetration and maybe to knock down any raised fibers that may cause different stain absorption.

From contributor R:
You can cut the B10 stain base up to 50% with lacquer thinner to help increase color depth. Let dry 15-20 minutes. You might also try the 2 1/2% Clear Spray Stain Base (WS2-SB2). Spray on a light coat. No need to wipe off. Let dry 15 minutes. Every wood reacts differently.

From the original questioner:
When you say let it dry 15 to 20 minutes, are you referring to the stain base before you wipe it? Or are you referring to the cinnamon stain before wiping?

From contributor R:
After wiping the base, let it dry about 15-30 minutes before wiping on the stain.

From contributor O:
Maple is a very popular wood for us to use in the cabinet shop, whereas cherry was the hot wood a few months ago. I get very good results finishing maple this way and don't have the blotchiness that's common. I thin down some vinyl sealer with 75% acetone. I apply two coats and let it dry. I then sand with 280 silicone carbide paper. I use a sander whenever possible and do what's left over by hand. I don't just scuff sand - I do a thorough sanding job. I then remove the dust (important step). We mostly mix our own colors, so if it's an oil color (depends on sample), I just brush or wipe on the stain, and wipe it off. On a door that has some detail, I wipe most of the stain off and manipulate the rest of it with a good, clean and mostly dry brush. If I do a color that's dark, I seal in that background color and tone it from there until I have my desired color.

P.S. When I wipe the stain off, I don't use a dry rag - I use a seasoned rag, one that's real moist, but not real wet. I save the seasoned rag in a tightly closed zip-lock bag and use it again for a similar color.

From contributor D:
I must admit, I have never tried using acetone for a washcoat. Is there a real advantage to it other than a faster flash off? And you stated that you sand it with 280. Do you find it takes too much of the washcoat off? I am accustomed to using 320.

From contributor M:

You have to be spraying way too much washcoat. Just one wet pass and that's it. As a learning tool, you may try a 4' board and mask off every 6" or so and step down your wash coat. The first 6" would be raw wood, then start at 10:1 (thinner to sealer) and step up till you get to 1:1. Let it dry and stain the entire board. You will then get a much better idea of how a wash coat works.

From Paul Snyder, forum technical advisor:
I've had good results with the cinnamon color without using a washcoat. Spray a light, even wet coat of the stain, let it flash and wipe the excess. If it does look mottled, try submerging your wiping cloth in the stain and then wringing it out back into the can before you use it. Using a clean, dry cloth or wiping the stain when it's too wet can contribute to blotching.

If you do go with a washcoat, thin the vinyl sealer down to 3% - 5% solids and use one regular wet coat on the bare wood. There's more info on adjusting the solids content at:
Related link: Make a Washcoat

Another approach that works well is to thin the stain with the clear stain base and use that on the bare wood. Then seal the stain, sand it smooth, and add some of the stain (e.g. 1-2 ounce per quart) to some thinned finish to make a toner. Spray a coat or two of the toner to add back the color and even it out and follow with a coat or two of clear finish.

From contributor T:
What is Scotch Brite?

From contributor L:
Scotch Brite is the equivalent of synthetic (plastic) steel wool.

From contributor O:
Not only does a good potion of sealer help out with the spottiness, but it's also important to sand your raw wood, not just scuff it. The cabinet shop sands the case goods with 180-220 grit paper (I don't let them touch the doors - my finishers do all the sanding on them). I make sure that they do a good job before shoving the project on to my department; no glue, no cross grain scratches and no swirls. I pretty much leave the case goods alone, but I do attend to any applied panels that will be attached to them. 280 grit paper is my choice in the finishing department. I sand the raw wood doors with it and I also sand my sealer coats with it. All sharp edges are eased and all sanding dust is blown off before I apply my first sealer coat. By starting out with a smooth surface on maple or cherry, I find that I can just about eliminate any of the blotchiness that's common to those woods. Another thing you might consider is a gelled stain. Lots of companies make them now and they can also help in conjunction with a sealer coat to prevent the blotchiness.

From contributor O:
I use acetone because it's an exempt solvent here in Arnoldfornia. I don't use L/T because it scoots the 550 gpl to one that's not compliant and I must follow the rules to a T in our shop. I use 3-M silicone carbide sandpaper Awt. and the 280 seems to work fine for me.

From the original questioner:
Thanks to everyone who has responded. I didn't have the B10 stain base like I thought, but I did have B20. I thinned the stain base down 4 parts thinner to 1 part stain. Brushed a coat on my material, let it sit for about 5 minutes, wiped it off and let it air dry for about 1/2 hour. I then brushed, not sprayed, my MLC Cinnamon stain on and let set for around 10 minutes. Wiped the stain off and voila! It looks great. I sealed with a coat of vinyl sealer, let dry, sanded lightly, applied a coat of MLC Traditional Glaze in Van Dyke brown, let sit for 5 minutes, brushed it in with a dry brush to achieve the look I wanted. Sealed again, and it looks great. I can't believe I finally found a solution to use on birch and maple. I will try the suggestion of wash coat thinned about 8 to 1 sometime. I think that has been my problem - too many solids and too heavy of a wash coat.