Rule 27 of 31 · Chapter VI — Finishing and Shop Habits
Test the finish on scrap
Why this rule exists
The finish is the part everyone sees, and it's the least forgiving to undo. Color that looks great in the can can go muddy or blotchy on your actual wood, and a topcoat can react with a stain or raise grain you didn't expect. A scrap test, same wood, same prep, same product, shows you exactly what you'll get before you commit it to the piece you spent weeks building. Ten minutes of testing beats stripping a tabletop by hand.
In practice
Keep offcuts from your project prepped the same way as the real parts, sanded to the same final grit so the surface behaves identically. Try your whole finishing schedule on them, conditioner, stain, and topcoat, and let it dry fully to judge the true color and sheen, which both shift as they cure. Test how many coats give the look you want and confirm your application method behaves. Only when the scrap looks right do you lay a brush on the actual workpiece.
When it doesn't apply
A clear finish you've used many times on a familiar wood may not need a fresh test each time. But any new product, new wood species, new stain, or a color you're matching absolutely warrants a sample. When in doubt, test; the cost is a scrap and a few minutes against redoing the whole piece.