Shellac by the batch, not the gallon: flakes and alcohol for any pound cut, how much alcohol drops a 3-lb cut to a 1-lb washcoat, and simple percentage thinning.
8 oz = 1 cup · 32 oz = 1 quart
Weigh the flakes, pour the alcohol over them, and swirl the jar every time you walk past — flakes dissolve overnight without stirring vigils. Strain the mix through a paint filter or cheesecloth before use to catch wax and stray bark, label the jar with the cut and date, and store it out of the sun. If a batch thickens over the months, this calculator’s dilute mode brings it back to a working cut.
Pounds of shellac flakes dissolved per gallon of alcohol: a 2-lb cut is 2 pounds of flakes in one gallon. It’s a ratio, not a batch size — this calculator scales it down to shop-size batches in grams and fluid ounces, since nobody mixes shellac by the gallon.
A 1 to 1½-lb cut for washcoats, sealing, and blotch control before stain; a 2-lb cut as the everyday brushing and padding finish; 3-lb for filling and building quickly. When in doubt, mix a 2-lb cut and thin from there — thinning is a one-way trip that’s easy to make.
Denatured alcohol (sold as “shellac thinner”) is the standard. High-proof grain alcohol works and smells better but costs more; either wants to be 190-proof or better — water in the alcohol turns shellac cloudy. Isopropyl from the pharmacy is 30% water: don’t.
Mix what you’ll use in a few months. Dissolved shellac slowly esterifies and eventually won’t harden — test old shellac on scrap and if it’s still tacky the next morning, it’s furniture polish now, not finish. Flakes in a sealed jar keep for years.
Only when something else goes on top: polyurethane and some waterborne finishes bond poorly to shellac’s natural wax. Dewaxed flakes (or “SealCoat”) under other finishes; waxed is fine as the final finish and rubs out beautifully.
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Species + board width + humidity swing → how much that panel will expand or shrink, flatsawn vs quartersawn.
Thickness × width × length → board feet and cost, with the 4/4–8/4 quarters convention explained inline.
Parts list in, cutting layout out — sheet goods or boards, with kerf, grain locks, waste %, and a printable diagram.