The potting solution that’s used to seal the coils can flake when turns of magnet wire are removed. The wax or other solutions can become hardened and dry out with age. The best thing I found to make it look better is to use a hot hair dryer or carefully use a heat gun. The heat gun is used for shrink tubing and can get very hot! Wear glasses and try not to get the gun to close to the pickup. The heat from the gun will melt the outer coatings and make the wax flow evenly around the coil. If you get the gun too close to the pickup, the force of the hot air can blow the wax all over the place. Keep it at a safe distance.

When removing turns of magnet wire from the pickup the hardened wax can flake. When trying to remove turns of magnet wire and they keep breaking, use a small bit of lacquer thinner on a Q-Tip to soften the outer layers of coil. Then use an old tooth brush to remove the loose or broken turns. When unwinding you can end up with several ends of magnet wire and by carefully unwinding you should eventually end up with one. Check to see that you have continuity or around 8.3 K ohms DC Resistance per coil for old Stringmaster pickups. The old pickups are hand wound with 42 Plain Enamel.