Hard, Smooth, and Nonabsorbent Surfaces(tiles, glass, lacquered/painted wood): Use Carbon or Charcoal powder for light-colored surfaces. Use grayish-white powder for dark surfaces). Fluorescent powder, visible under ultra-violet light, can also be used. The powder will stick to the sweat and oils left behind and leave a visible print that can be lifted.
Soft and Porous Substances (cardboard, paper, cloth): Chemicals are used, such as Iodine, Silver Nitrate, and Ninhydrin. Iodine is used in a fuming process to photograph the prints. Silver Nitrate can be used a last resort when other methods do not work as it renders the other tests ineffective. A 3% solution is dusted on the print and then an ultraviolet light will reveal the prints as reddish-brown. Ninhydrin is made into a .6% solution by dissolving it in ethyl alcohol or acetone and sprayed on the print, causing it to turn dark purple in an hour or two.
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