Washcoat and Stain Issues with Birch and Maple

      A birch-plywood cabinet with maple face frames poses a tricky staining problem. Here's a little explanation about washcoats, stains, toners, and more. April 9, 2007

Question
I’m having trouble getting a nice finish on a bookcase. The box is built of birch and the face frames are maple. I sanded all to 180, dyed all with fairly dark oak Microton dye. That looked nice. Everything was even shaded to match. Then I wash coated with 50/50 Magnalaq and lacquer thinner. Sanded with 320 and began to stain with MLC traditional cherry. This is when the problems started. The birch didn’t stain very evenly and the maple didn’t want to take the stain. I spent over an hour on each bookcase trying to get an even color. Where did I go wrong? I did several test panels prior to starting and they seemed to go fairly well – they were even, and color was good. So I am sort of baffled. I had tried a conditioning coat on a test panel with the b-10 stain base and it didn’t seem to have much effect.

Forum Responses
(Finishing Forum)
From contributor O:
I believe your 50/50 wash coat was too strong. You effectively sealed the birch ply, precluding its ability to absorb (evenly) the Woodsong stain. Go to the Knowledge Base and search for “wash coat” and the appropriate recipe for reduction.



From the original questioner:
The 50/50 was was per MLC rep.


From contributor G:
I used to run into this problem trying to use Microton toners under WSII. Some of the WSII stains have a lot of Microton in them as opposed to pigments. The Microton toner has a resin content of its own and the high Microton-content stain re-dissolves this resin in the toner. Find another way to get your color. Traditional Cherry over Dark Oak toner?


From the original questioner:
What would you suggest to achieve the dark reddish brown color when staining over a light colored wood? I used the dark oak to keep the yellow down from the birch and the traditional cherry for the dark red.


From contributor G:
It's kind of difficult to match your color from here, but I'll give you tips. To kill yellow, you need purple, which will make it brown. You want reddish-brown, so use a purple slanted towards red; something like 1 pt Microton red to 4 pts Blue and 20 pts thinner. (I know, but red is stronger than blue.) This will kill the yellow pretty fast, so you don't need much. Let it dry, and try staining without sealing it in. If I recall correctly, red and blue Microtons are dyes, while Dark Oak is a microlith, so theoretically the dyes will bite into the wood better and not require sealer. The WSII will also bite in better. If you find you do have to seal it, thin down your wash coat.


From contributor T:
At 1:1, your first coat was 16% solids - a good first seal coat which may be what your rep thought you wanted. But a wash coat should be down between 5% and 10% solids followed by a light sanding. It should fill the thirsty pores but not fully seal the wood. You should be thinning Magnalac 4:1 for a wash coat. Then you sanded with 320? That does little more than knock off the nibs, leaving a nicely sealed surface with little or no tooth to pick up stain. I suspect that your uneven stain take was a result of surface roughness variations. If you want to fix it, I'd suggest re-sanding to the wood (but not into it) with 180. Then stain again. Another solution would be to mix some dye into your finish and tone the whole case.

I always work from lighter to darker colors in a finishing schedule. For a cherry look, I start with a light red or pink dye to get a uniform background color. Follow that with your wash coat, sanded with 180, and then a darker stain and maybe a glaze or toner if needed to get the color and look you want.

One of the threads under a "wash coat" search contains input from Paul Snyder
about wash coats, stains, and glazes to produce a very attractive cherry finish. Worth reading.



From the original questioner:
I greatly appreciate the insight! I believe the main problem was the wash coat. I had asked the rep to make sure and he told me that 50/50 was a good mix. I also asked him about dying red and staining with brown rather than brown dye and red stain. Well, I guess this is a lesson learned. A very expensive and timely lesson learned. I am going to try some test panels with this information and see how it works.


From contributor G:
When I worked for the MLC distributor, we made stain matches and finishing schedules all day long and sometimes on weekends for our customers. Does your rep offer this service?


From contributor R:
I would like to make a couple of comments. First off, there is no resin in Microton dye. Second, all of the dyes are made from the same 5 dye concentrates. So there is no chemical difference between oak and tinter red, only the color. Some wiping stains do have some of the dye concentrates in them, but not the reduced Microtone dye that you would buy.

It is true that the solvent in the wiping stain can lift the dye in some instances. That is why a wash coat is usually recommended. The situation where this is most imminent is when the dye is not reduced enough or applied very heavily. In this instance, the dye tends to sit more on the surface of the wood and is not absorbed into the fibers as much, and thus is more prone to rewetting by the stain. A good reduction for the dyes is about 2 to 3 parts thinner to 1 part dye. Spray light coats and let each coat flash off before applying the next.

I think part of the difference you saw between the birch and maple has more to do with one being a veneer and the other a lumber. Most veneers take stain darker than their lumber counterparts – this is due to the fact that most veneers are steamed before slicing.

That brings us to the wash coat. The two controlling issues when it comes to a wash coat is how much you reduced it and how heavy you put it on. In the end, it is about dry mil thickness. The difference in application might explain why the test panels came out okay but the finished product did not. You might not have put enough wet mils of the wash coat on the veneer – thus the blotchiness. Again, the lumber is going to need less wash coat because it doesn't take stain as dark to begin with. Sanding the lumber with a coarser grit than the veneer is one technique that will help.



From contributor G:
I certainly don’t want to get into a technical argument with you over the properties of Microtons. I see on the MSDS that there is 2-5% solids by weight and I thought those were resins. I also notice that dried Microton residue is flaky and film-like. I wonder if there is a different formula used between the US and Canadian versions.


From the original questioner:
That makes plenty of sense. I laid the dye on very heavy over several passes not thinned at all. I also put a little too heavy of a coat of wash on. What is your insight on getting the dark color on maple as far as dye - brown or red, and staining the opposite or eliminating the dye and using the b-10 to condition and stain with a color?


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