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A Black Powder Method To Process Adhesive Tapes
ROBIN BRATTON
JEFF GREGUS, Student Intern (This information was distributed at a recent F.B.I. course, and submitted by George Durgin, Escondido Police.) After evaluating a number of soap/powder combinations the following formulation was found to be the most effective on a broad spectrum of tapes and is easily produced and stored: 20 drops water (tap water is adequate) 20 drops Liqui--NOXTM glassware soap (available from most laboratory supply companies) 0.5 gram Lightning Black Powder (Lightning Powder Co., Inc., Salem Oregon)
The solution is stirred in a shallow container, such as a plastic weighing boat or petri dish, until it has the consistency of shaving cream with small bubbles. The solution is “painted” on the adhesive surface with a camel hair brush and then rinsed off with a slow stream of water and allowed to dry. The single modification that offers some benefit is with black tapes. In order to provide sufficient contrast, after rinsing off the black powder mixture, the tape is painted with a similar mixture of gray powder, rinsed, and any prints developed photographed. Another option with black tapes is to lift the developed prints with lifting tape immediately after the gray powder application by placing the two adhesive surfaces together and then peeling them apart. The lifting operation must be done while the tape is still wet to prevent the two adhesives from sticking together too tightly. While carrying out the comparison studies, it was observed that the mixture can be prepared and the water allowed to evaporate producing a dry material easily stored and transported. It is readily reconstituted by addition of water until the desired consistency is reached. It is sometimes helpful to grind the dried material in a mortar before adding water.
This article was reprinted in “THE PRINT” |