CONSERVING A CRACKED 78 RPM RECORD
We want to make the record stable and prevent the crack from getting worse. We also want to make it sturdy enough to play casually. This record had a clean crack almost to the label.
Use a few wood blocks and a clamp to hold the record flat at the crack area. This will prevent/reduce tick sounds at the crack when completed.
We will prevent further flexing and possible cracking by hold the outer edge as firm as possible with epoxy. First, file a notch (used a round file here) close to, but into the first grooves. Check both sides.
Put piece of "Scotch" tape on the bottom of the notch and covering well the grooves on the bottom. Mix "5 minute" epoxy with a little black powder pigment. Carefully place some epoxy into the hole and, using a toothpick, maneuver it right up to the edges of the notch.
After an hour, trim the spillover epoxy with a razor knife, and form a tape dam on the edge with more tape. the fill in with some more black epoxy mixture.
After a few hours, use a razor blade window scraper to carefully slice off the bubble of epoxy on both sides. Then put the wood pieces and clamp on overnight to let the epoxy get rock hard.
Similar methods can be applied to conserve fragile edge chips.