Len - there are multiple reasons colorings blotch. Incompatible
products, incorrect preparation, and the worst - contamination.
Contamination can come from anywhere. It could be on the ply when you
buy it, it could be something in your finish, or it could be as simple
as using a rag from the rag bag instead of a clean rag.
The love of my life put softener in every load, even those destined
for the rag bag, so they are loaded with silicones and other agents.
If you are having problems with "terrible" blotching after your
sealer, there is a easy way to test that will give a good idea (not
foolproof) of contamination. Try this to see if you are having a
compatibility or contamination problem.
Put some colorant in a clean spay bottle. You can get these at the $1
store, and it will be worth a buck to see if this is the problem.
Spray it on a couple of the LIGHT areas, not the dark. If the
colorant beads up on the surface into a million little beads, you have
a problem. If it lays flat and simply shrinks at the edges, you are
If you have a contamination problem, start over. Even if you spray a
toned finish on a contaminated surface and it looks fine when
finished, it may not hold up. Finishes today are so good they will
fool you for a while by looking great. But if they don't adhere
properly, there will be problems later.
Birch ply in particular can be tough to get right.
The biggest alarm bell you sounded though was the fact that you were
using a water based dye on top of shellac. Depending on how you
applied your shellac, and how much you sanded, etc., your shellac will
have different levels of porosity and water repellance. Think about
this; if you set a sweating glass of water on a table for a few of
minutes, the water won't penetrate as it has some water repelling
This could easily be the problems with your dye.
And if you are apply the dye with a rag, brush, pad, or anything else
by hand, the dye will be sucked out of the applicator by the more
porous areas of the ply. You don't stand a chance at an even
If it were me, I would recreate exactly what I now have on a few
pieces of scrap. Then i would work on a solution, whether it be
sanding and recoloring, toning, changing finishes, etc. Just applying
a mask over the existing "terrible blotching" may mitigate the poor
appearance, but then you will be making excuses for your work any time
you show it off.
Don't think applying a toner is that easy, either. A tiny bit of
color applied well is in fact pretty easy. But if you are applying
enough color in a finish to cover up problems, you are essentially
adding a thinned, colored paint. Again, try this on your prepared,
blotchy scraps and see what you think before going to your project.