Understand the difference between these often misused terms.
By Bob Flexner
Pages 60-62
It would be difficult to find wood finishing subjects that have been made more confusing than sealing and washcoating. This is unfortunate because these procedures are very simple and easy to understand.
Definitions
A sealer is the first coat of finish you apply to the wood. It enters the pores, dries and stops them up so liquids don’t penetrate easily. It “seals” the wood. The sealer can be the finish itself (any finish), or it can be a special product designed to solve a problem.
A washcoat is any finish thinned to 10 percent-or-less solids content and used to partially stop up the pores in the wood (so a stain will still add some color), or provide a thinner barrier between color coats (stain, glaze, filler or toner) to limit the total finish build. The commercial varnish product labeled “wood conditioner” is a washcoat.
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