Don Casey Tip #36  

Varnish Build-Up Coats

Scratch through the topcoat of almost any painted surface and you will find an underlying primer coat. Primer prepares the raw surface for the paint. The result is a better finish.

It is useful to think of varnishing as a similar two-step process. With varnish we don't use the term primer, but we could.  Varnishing raw wood always begins with several so-called "build-up" coats, and these perform almost the same function as primer under paint. We want the build-up coats, first and foremost, to get a good grip on the wood.  After that, we want them to level out the surface, filling the wood's pores.  We also want the build-up coats to clarify the wood, bringing out the beauty of the grain.

You can use the same varnish for both build-up coats and finish coats, but the pros often use a less expensive varnish for the build-up coats. Only color and clarity matter; flow, gloss, and UV resistance do not become an issue until we get to the topcoats. For a foot-deep finish, plan on applying six build-up coats followed by three or four carefully applied finish coats.