Rule 28 of 31 · Chapter VI — Finishing and Shop Habits
Build finish in thin coats
Why this rule exists
Everybody wants to be done in one heavy coat, and everybody who tries it gets runs, sags, drips, and a gummy surface that stays tacky for days. Finish cures from the surface inward, so a thick coat skins over and traps solvent underneath, never hardening right. Thin coats flow out level, dry fully, and stack into a deep, even film. Two or three thin coats always beat one thick one, and they're far less work to fix when a bug lands in them.
In practice
Thin your finish if it needs it and apply light, even coats, wiping or brushing without flooding the surface. Let each coat dry fully, longer than you think you need, before laying on the next one. Scuff lightly with fine sandpaper or a synthetic pad between coats for adhesion and smoothness, then wipe off all the dust. Work in a dust-free spot with good light raking low across the surface so you catch misses, runs, and holidays while they're still fixable.
When it doesn't apply
Some finishes are built to go on heavier: a single flood coat of thick wiping varnish or a self-leveling pour is by design. And penetrating oils are wiped on and back off rather than built up at all. Match your approach to the product, but for film finishes like varnish, lacquer, and poly, thin and patient wins.