12.6: Serial number restoration

Serial number restoration is, aside from being a fun thing to do, a form of impression evidence recovery. When a number is stamped into plastics or metals, the molecules are compressed at a different rate than the surrounding area. Therefore, when the number is obliterated, it is possible to recover the number by using acids that slowly dissolve the uncompressed molecules surrounding the compressed molecules and thus revealing the number. The trick is to be very careful how you file smooth the obliterated area. This must be done by hand using an Emory board and extra-fine sandpaper. Do not use a drill-mounted wire brush or Dremel tool as this will excite the molecules in the compressed area and the process will not work. Once the compressed area is glass-like smooth, build a dam using molding putty around the compressed area and apply the acid that is specific to plastics, aluminum, steel, or copper. Patiently allow the acid to reveal the number (it may take several applications) and then neutralize the area using a pH neutralizing agent like baking soda. Photograph the resulting recovery quickly as the acids may continue their work regardless of the neutralizing agent.

 

 

 

 

 

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