Carbon Resistance Ring: Laminated Paper Gelled with 10% Tung Oil, Graphite-Shellac Track

Mallory's quiet volume-control ring (US 2,144,925, 1939). Hard bases were noisy and soft paper ones changed with damp. Their answer: paper rings soaked in 10 % raw tung oil and baked, so the oil gels inside the paper. It shuts out moisture but stays soft and springy, and the wiper runs on it quietly. A graphite paint makes the track, silver paint the ends. The picture: the patent's drawing (Fig. 3).