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Advances in Fingerprint Technology.pdf

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An alternative technique was proposed by Barron, Haque, and Westland 11 <strong>in</strong><br />

which a freeze and thaw method was used before dust<strong>in</strong>g with f<strong>in</strong>gerpr<strong>in</strong>t<br />

powder. James et al. milled alum<strong>in</strong>um-based and other powders to determ<strong>in</strong>e<br />

the optimal particle size (5 to 10 µm long and 0.5 µm thick) and stearic acid<br />

content (3 to 5%) for latent f<strong>in</strong>gerpr<strong>in</strong>t development. 12<br />

A variation on the usual powder dust<strong>in</strong>g procedures, but which can<br />

nevertheless be considered a k<strong>in</strong>d of “powder” development technique, was<br />

described by Waldock. 13 A camphor candle was used to produce soot that<br />

could “coat” the latent pr<strong>in</strong>t.<br />

Organic F<strong>in</strong>gerpr<strong>in</strong>t Powders<br />

Many commercial f<strong>in</strong>gerpr<strong>in</strong>t powders conta<strong>in</strong> toxic <strong>in</strong>organic chemicals<br />

such as lead, mercury, cadmium, copper, silicon, titanium, and bismuth.<br />

Long-term exposure to them may present a health hazard. The use of organic<br />

f<strong>in</strong>gerpr<strong>in</strong>t powders for latent pr<strong>in</strong>t dust<strong>in</strong>g was suggested by Kerr, Haque,<br />

and Westland. 14 A typical powder formula consists of the follow<strong>in</strong>g:<br />

Potassium bromide 1 g<br />

Cornstarch 35 g<br />

Distilled water 25 mL<br />

The procedure that was used to prepare the organic f<strong>in</strong>gerpr<strong>in</strong>t powder<br />

was as follows:<br />

1. Dissolve 1 g potassium bromide <strong>in</strong> 25 mL distilled water.<br />

2. Slowly dissolve 35 g cornstarch <strong>in</strong> the above solution with constant<br />

stirr<strong>in</strong>g.<br />

3. Dry the cornstarch mixture at room temperature for 7 days.<br />

4. The solid mass is periodically ground with a mortar and pestle over<br />

the dry<strong>in</strong>g period to produce a f<strong>in</strong>er powder.<br />

5. The powder is stored <strong>in</strong> a tightly stoppered conta<strong>in</strong>er conta<strong>in</strong><strong>in</strong>g anhydrous<br />

calcium sulfate as a desiccant.<br />

It was reported that cornstarch-based f<strong>in</strong>gerpr<strong>in</strong>t powders yielded excellent<br />

results <strong>in</strong> develop<strong>in</strong>g latent pr<strong>in</strong>ts on nonporous surfaces. In addition to<br />

regular cornstarch f<strong>in</strong>gerpr<strong>in</strong>t powders, the same research group also<br />

reported on the use of organic-based fluorescent powders for latent pr<strong>in</strong>t<br />

detection. 15 The follow<strong>in</strong>g are several organic-based fluorescent f<strong>in</strong>gerpr<strong>in</strong>t<br />

powders as reported by Kerr et al.: 15<br />

Calcium sulfate 5–10%<br />

Dihydrate cornstarch 90–95%

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