Burn-In

The period-correct repair — a melted resin, a heated knife, and a defect filled with material the rest of the piece already understands.

Burn-in is the old way of repairing a finish defect — a gouge, a chip, a worn corner — by melting a stick of solid shellac-and-rosin directly into the wound and leveling it with a heated knife. The repair fuses into the surrounding finish because it shares the surrounding finish's chemistry. Done well, the eye cannot find it. Done with the wrong material, the eye finds it on every coat.

The sticks on this page are made from shellac, Brazilian gum rosin, and pigment — the chemistry the trade settled on in the 1930s and has not improved on since. They are produced in small batches, one tone at a time, by a maker who has been at it for twenty-five years.

What burn-in actually is

The finisher heats the tip of a burn-in knife over an alcohol lamp or a small torch. The hot blade is touched to the end of a colored stick, melting a bead of the resin. The bead is laid into the defect, and the warm blade is drawn across the surface to level it. As the resin cools it sets — a true thermoplastic film, repairable on the next pass, compatible with the shellac, oil, and varnish films around it.

Most of the trade has settled for synthetic-resin sticks — plastic markers, in effect, that fill the hole but never marry the surrounding finish. They are easier to make and cheaper to ship. They are also visibly wrong on antique pieces and on instruments, where the patch does not age, does not move with the wood, does not take a new coat of shellac the way the original surface does.

The chemistry on this page is the older chemistry. The result is a repair that belongs in the piece.

Who uses them

Furniture restorers — period repair on eighteenth-, nineteenth-, and early-twentieth-century pieces, where the patch has to age with the original.

Instrument repair shops — guitars, violins, mandolins, the whole stringed-instrument world. A burn-in patch on a French-polished surface can be polished over the same day.

Conservators and museum technicians — reversible, repairable, chemically compatible with the original finishes they encounter on institutional pieces.

Finishers who keep a small kit on the bench for the inevitable nick — the knife, a roll of sticks across the working tonal range, an alcohol lamp.

What we carry

Sticks are sold individually across the tonal range, and as sets — the Merit Full Set 18 covers the full working palette, with smaller sets for finishers who want a starter range. The heated knife is sold separately; many practitioners already own one.

If you would like a recommendation for a specific job, an email or a phone call will get you a real answer from someone who knows the material.

Browse the sticks, sets, and knife below.