# The Finish Hewn Shop Notes · https://hewn.build/shop-notes/the-finish AI-drafted, not yet checked: Drafted by Chip, the writing system Hewn runs on Claude, from Hewn's craft corpus. Jonathan Salomons has not read this note yet, and no outside reader has checked it. Read it as a shop note: check a number before you cut to it. Cite as: "The Finish." Hewn Shop Notes, hewn.build/shop-notes/the-finish. Drafted 2026-05-01; AI-drafted, not yet checked. --- Most people pick a finish when the piece is done. The wood is built, sanded, sitting there. They walk to the shelf, read a few labels, pick something that sounds right. Apply it. Hope it comes out. That's the wrong order, and by the time you figure out it's wrong, you're either spraying finish inside a carcass you've already glued up or refinishing a surface you needed to prep differently three steps ago. The finish decision shapes everything before it. Make it before you cut the first board. --- Here's what a finish actually does, because "protects and looks nice" is not useful. A finish controls two things: what gets into the wood, and what the surface looks like. Those are related, but they're not the same thing, and different finishes prioritize them differently. **Penetrating finishes** — oils, wax — soak into the wood fiber and cure there. No film on top. Touch a piece finished with oil and you're touching the wood, not a layer above it. The protection works from the inside out: the finish occupies the space moisture would otherwise use, which slows down MC swings. It doesn't stop them. The wood still moves. **Film finishes** — lacquer, polyurethane, shellac, conversion varnish — build a layer on top. The wood is sealed under glass. Moisture exchange drops sharply. Scratches happen in the film, not the wood. The protection is armor. Neither is better. They're different tools. Knowing the tradeoffs is what finish selection actually is. --- Penetrating finishes are forgiving to apply and easy to repair. They need reapplication every few years, especially under UV and hard use. They're right for anything where you want the surface to feel like wood — chairs, tool handles, tables that see hands every day. They're wrong for surfaces that take repeated moisture exposure or for cases where long-term protection matters more than feel. Film finishes are harder to apply well. When they fail, they fail unevenly — crazing, peeling, lifting — and the repair is stripping back to wood and starting over. Get the application conditions wrong (too cold, too humid, recoating too soon) and you'll know it. They're right for cabinet doors, fine furniture built for longevity, anything where the surface needs to last decades without maintenance. Wrong for anything where easy refinishing is part of the plan. --- There's a third category that doesn't fit neatly into either: shellac. Shellac builds a film like a film finish. But it dissolves in alcohol, which means it's reversible. Repairs are straightforward. Compatibility with other finishes is nearly universal — shellac goes under anything. Oil, lacquer, wax, poly. Nothing rejects it. That's why every finisher who's been at this for more than a few years has shellac on the shelf regardless of what their primary system is. It's the most useful finish in the shop even if you rarely use it as a topcoat. It gets its own treatment elsewhere. It's mentioned here because the penetrating-vs-film framing leaves a gap without it. --- The question to answer before you start sanding: *What does this piece need to do for the next twenty years, and who's going to care for it?* A kitchen chair that gets wiped down weekly needs something different than a display cabinet that gets dusted twice a year. A commission for a client who will never refinish it needs something different than a piece for a maker who'll maintain it themselves. That answer also changes your build sequence. Film finishes are often easier to apply before assembly — the inside of a cabinet box is a lot more accessible before the sides are glued up. Penetrating finishes can usually go on after. Decide late and you're working around a problem you could have planned past. --- A sensible default for most shop furniture is a penetrating oil — usually a tung oil blend for indoor pieces, with shellac as a sanding sealer under everything. Use film finishes when a client specifies them or when the design requires it. Wipe-on poly is a good go-to for horizontal surfaces that need real protection without a spray setup. A cold Interior BC shop creates its own application constraints. Temperature changes everything in finishing. That's its own conversation. For now: decide the finish before you start building. It's a design decision. Treat it like one.