# The Finish Selection Protocol Hewn Shop Notes · https://hewn.build/shop-notes/the-finish-selection-protocol 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 Selection Protocol." Hewn Shop Notes, hewn.build/shop-notes/the-finish-selection-protocol. Drafted 2026-05-03; AI-drafted, not yet checked. --- Most finish decisions fail before the can is opened. Someone picks a finish because they used it last time, or because the label looked right, or because that's what they had on the shelf. It performs correctly in one dimension and fails in another — the right protection on the wrong species, or the right family with prep it couldn't survive. Then they blame the finish. Here's the frame that prevents that. Four questions. Ask them in order. The first one mostly determines the answer. The rest narrow it. --- **Question 1: What is the substrate?** Species. Porosity. Chemical properties. Color layer planned or not. This is the compatibility question. Every other decision depends on getting it right. Ring-porous species — white oak, red oak, ash — have large open pores that raise dramatically under water-based finishes and require pore-filling before any gloss film. Close-grained species like hard maple and birch do not. Same finish, different prep requirement. If you don't know the species, you can't build the right plan. Some species contain extractives that fight certain finishes. Teak and rosewood carry oils that prevent oil-based coatings from curing. You apply the finish, it stays tacky for two weeks, you panic. The problem wasn't the finish. It was the wood-finish pairing. Pine knots bleed resin through clear coats without a barrier. These aren't obscure edge cases — they're the things that produce callback jobs. If you're using a colorant, resolve that now. Oil-based stain under a water-based topcoat requires a dewaxed shellac barrier. Don't find out the hard way. --- **Question 2: What is the primary protection requirement?** This question picks the finish family. The use context does most of the work. High abrasion — dining tables, kitchen work surfaces, chair seats — needs a film finish. Penetrating oils will not protect adequately under cyclic abrasion. The only question is OB poly versus WB poly. Moderate interior use — case pieces, shelves, most furniture — gives you room. Film finish is appropriate; oil finish is acceptable if water exposure is low. Water resistance requires a film finish. Shellac and wax are not waterproof. OB poly outperforms WB poly in wet environments. UV exposure needs a finish with UV absorbers. Spar varnish for high exposure. Dye-only color systems will fade without a UV-absorber topcoat above them. Exterior use means spar varnish. No interior finish is rated for outdoor exposure, regardless of what the label implies about "durability." --- **Question 3: What are your working constraints?** Constraints don't change the structural requirement. They determine which finish within the right family is achievable in your shop. No spray equipment means lacquer is off the table. WB poly and OB poly can both be brushed or wiped; lacquer cannot be applied by hand at production quality. Cold shop changes everything. WB poly won't coalesce below 55°F. OB poly cure is dramatically extended below 60°F. If you're finishing in an unheated shop in October, temperature may eliminate a finish option. Ventilation: lacquer requires it and requires an explosion-proof fan for solvent vapors. If you can't provide that, WB poly is your low-VOC option. --- **Question 4: What is the appearance target?** Last. Always last. Not because it doesn't matter, but because appearance alone shouldn't drive the system. Amber shift: OB poly warms and deepens. On walnut or cherry, that's an asset. On hard maple or birch, it yellows in a way most people don't want. If clarity matters, WB poly is the call. Sheen level is a product specification, not a family specification. Every major finish family comes in flat through gloss. Pick sheen after you've picked the system. Natural feel: penetrating oils leave wood feeling like wood. Film finishes leave a detectable surface at thicker builds. If the piece is meant to be held or handled — a plane tote, a chair arm — oil maintains the tactile character. Poly doesn't. --- **Three decisions, applied** *White oak dining table, home.* Ring-porous, high abrasion, brush application, clarity preferred. Answer: WB polyurethane, four coats minimum. Grain-raise pre-treatment is mandatory, not optional. Between-coat sanding at 320. OB poly would amber the white oak's cool tone — wrong call for this application. *Walnut kitchen cabinet, wall-mounted.* Moderate interior, brush application, warm tone acceptable. Answer: OB polyurethane, two to three coats, thinned 10% for the first coat. The amber deepens walnut's figure. WB is technically adequate here but doesn't earn anything OB doesn't. *Cherry bedside table, shellac re-coat.* Denatured alcohol test confirmed the existing finish is shellac. Light interior use, brush application, match existing character. Answer: dewaxed shellac, one to two lb cut, one to two coats. Shellac resolves into itself — this is the easiest re-coat in woodworking. If the sheen reads too high after re-coating, 0000 steel wool and paste wax, buff to matte. --- **The hard rules that override everything** Wax present: strip before applying any finish. No exceptions. Oil colorant under WB topcoat: dewaxed shellac barrier is mandatory. Not optional. Unknown existing finish: strip to bare wood or apply dewaxed shellac barrier before anything else. Blotch-prone species with pigment stain: gel stain, pre-conditioner, dye first, or work with the species. There is no shortcut here. --- The finish is a coating decision. Know the coating job before you open anything. Seven posts in this arc for a reason — the protocol is only as good as the decisions it organizes. Know your wood, know the use, know your shop, and the answer narrows fast. It's not complicated. It's just sequential.