A friend emailed me with this question: “What do you use on birch plywood to get it to take a stain evenly without blotching?
My first solution was to not use birch plywood if the plan is to stain it. This is something I’ve written about many times. When choosing a wood for a project, think ahead to how you want to finish it. Doing this may influence your choice of woods. Using birch plywood is not a good choice if your intention is to stain it.
What if it’s too late; the project is already built? The usual solution is to apply a washcoat before staining. The product sold as “wood conditioner” is a washcoat. It is a thinned finish, say two parts thinner to one part finish. The higher the ratio of finish to thinner the better it blocks stain penetration into the swirly grain of birch and the less the blotching. But also, the lighter the resulting color.
A better solution is to spray the stain and not wipe off the excess. This will leave an even coloring everywhere, even over the swirly grain. But the look will be quite different from that achieved by wiping off the excess stain. Brushing the stain and not wiping off the excess may work somewhat, but spraying is best. Brushing will leave brush marks, and brushing back and forth will have an effect similar to wiping off the excess.