[box]I bet you’ve seen the warnings on polyurethane varnish cans like “Do not apply over shellac.” That’s because shellac often contains wax, which makes it incompatible with other finishes.[/box]
When the wax is removed, these adhesion problems disappear and you have one of the most useful tools for finishing at hand.
Dewaxed shellac works perfectly as a coat between finishes that are not compatible. If you want to put water-based poly over an oil stain, you need to use dewaxed shellac between them. Want to put a fresh coat of finish on an old piece? Use a coat of dewaxed shellac on top of your old coat without stripping it.
Dewaxed shellac also makes a good barrier coat. It keeps the stains from blotching and colors from mixing and separating on different layers.
You can buy liquid dewaxed shellac in a can, but the most popular option is flakes because of their stability and ease of storage. There are also spray cans of dewaxed shellac available.
Whether you spray it on or brush it on, dewaxed shellac dries within two hours and is a great addition to your shop arsenal.