Rubbing the pick guards front surface with Acetone. Acetone melts celluloid. What we are doing here is not really cleaning but removing a thin layer off the top. You can clearly see the Yellow effect doesn't go to far into the material itself but is living mostly on the surface. This is also a way to determine whether a guard is Celluloid (acetone has zero effect on PVC). Of course, you don't want to go this crazy or you'll ruin it like we did. For this experiment we had to trash this guard to get to the true color of the material. Lacquer thinner also melts Celluloid. Essentially, that's all Cellulose Nitrate is - a very solid lacquer.
The back acetone test shows the back surface is not nearly as discolored as the top. Again - very obvious since the back has not been exposed. There is some discoloration. Over 50 years there is going to be some light, sweat, smoke, beer, etc finding its way. Note the stretched screw holes. This guard has indeed been shrinking and pulling on its screws. Thus why its good to store Celluloid guards on a guitar or a surrogate board. Left to shrink freely it would soon no longer fit. The important lesson here is mint guards do not age from the black middle layer bleeding into the white layers. The mint hue was there from day one - is simply becomes darker as the exposed white layers age from the surface down. On the next page we slice right into the guard to demonstrate this fact once and for all.
Next> Slicing a piece off
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