with the application of powder. There are different powders for different surfaces, and are available in different colors and compositions. the best powder is one that shows the best contrast with the surface being examined. Black and Gray powders are generally best for most latent prints. The black powder is composed of black carbon or charcoal, which is why it is used on light-colored or white surfaces. The gray powder is composed of aluminum dust so it is used on dark-colored surfaces. Aluminum dust is also Applied to mirrors and metal surfaces that are polished to a mirror-like finish, because these surface's will photgraph black. The powders are applies lightly to a nonabsorbant surface with a fiberglass or camel's-hair brush, this will stick to perspiration residue/deposits of body oils left on the surface. Magnetic-sensitive powder is spread over a surface with a magnet in the form of a magna brush. While using this method it decreases the chance of damaging or comepletely destroying the print because the magna brush does not have bristles that touch the surface. Flourescent powders can also be used to develop latent prints, these will show under a ultraviolet light.Soft and Porous surfaces(Such as cloth, paper, and cardboard) are made visible by the treatment of chemicals.
The oldest method is iodine fuming, this is based on the fact that iodine has the property to sublime. When heated iodine can change from a solid crystal to a vapor without passing through the liquid phase. they take the suspect material and put it in a cabinet with iodine crystals. while heated, the vapors will combine with the constituesnts of the latent print and make it visable. However, once the process has stopped, the print will begin to fade, this is why it must be photographed or sprayed with a 1% solution of starch in water, which will turn the print blue and make it last for several weeks to several months. Another chemical used in silver nitrate, after it is applied ultraviolet light is used to develop the print. This is made possible because the chemical reaction between sodium chloride(left form Perspiration evaporating) and silver nitrate, this forms the colorless silver chloride. After a 3% solution is brushed onto the evidential object and exposed to ultraviolet light, a silver print will be shown as a reddish-brown or black color. Ninhydrin (triketohydrindene hydrate) is dependent on the chemical reaction to form a purple-blue color with amino acids present in trace amounts in perspiration. The 0.6% solution of ninhydrin powder with a suitable solvent, such as Acetone or Ethyl Alcohol. This is usually sprayed onto the porous surface with an aersol can. Prints begin to appear within an hour or two, and if heated in an oven or on a hotplate at a temperature of 80-100 degrees C, can be hastened. Another chemical treatment for Fingerprint development is super glue fuming. Using this method produces a white-appearing latent print. Super glue is approximately 98 to 99% 
cyanoacrylate ester. This chemical actually interacts with and visualizes a latent fingerprint. Cyanoacrylate ester fumes can be created when super glue is place on absorbent cotton treated with sodium hydroxide or by heating the glue. The fumes and the suspect material are contained in an enclosed chamber for up to six hours.With these various methods, the one chosen depends on the surface to be worked on. Powders should be selected when the surface is smooth, while chemicals for soft and porous surfaces. When attempting to utilize all of the chemical methods of development, one should use iodine fuming first, ninhydrin second, then silver nitrate, and finally super glue fuming if it applies. This is the procedure for optimum visualization because iodine fuming is not permanent, and if ninhydrin fails, silver nitrate can be used but will wash away all the fatty oils and proteins from the surface. Hence, silver nitrate is used last if super glue fuming is not used.
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