Preparing a Finish

Instead of working directly from the finish can, it’s a good idea to strain all finishes before application and dispense them into smaller containers. Thinning a finish for application is more accurately done using a viscosity cup, which is a small cup with a precisely machined hole in the bottom. To measure for proper viscosity, you time how long it takes a specific finish to drain from a specific cup (such as 16 seconds in a Ford no. 4 cup). Viscosity ratings are typically provided for various industrial coatings.

Applying Multiple Coats

With pure oil finishes and most oil/varnish blends, you can only apply a maximum number of coats before you’re just wiping off what you apply. Film-forming finishes all have a minimum number of coats that should be applied for durability. Low-solids evaporative finishes like shellac and lacquer require four or five coats. With high-solids finishes like…