There are a couple advantages and disadvantages to using iodine as a fingerprinting process. The first advantage is that prints obtained on an item such as paper are not usually permanent and no drastic changes are made to the paper or any writing on the paper as can occur with a process such as ninhydrin. This is also a disadvantage as you are, more than likely, going to need some camera equipment to take photographs of the prints as they appear. You can obtain some chemical "fixers" that will set an iodine print so that it will not dissipate with time.

The second disadvantage to using iodine is the reaction component, fat, which is one of the first components to break down and be lost in a latent image where as ninhydrin reacts to amino acids which will be present much longer than fat substances.

To use iodine in the field to print a document such as paper you can place the document in a plastic sealable bag such as a large zip-lock bag with a very small amount of iodine crystal. Seal the bag and then gently shake the back back and forth horizontally (so the crystals stay at the bottom of the bag). This will generate enough heat so that the crystals will begin to evaporate and the prints will develop, literally, before your eyes.

Once completed you can put the any remaining crystals back into the container in which you store them as the crystals can be re-used. Another method you can use is to make an iodine fuming gun (or purchase them). The fuming gun allows you to print items which cannot be placed in a bag or fuming chamber if you have one. To make a fuming gun you will need iodine crystals, some glass wool, a moisture reducing component such as calcium chloride, and tube like material (the large shake straws used by some fast food places work well). When you blow through the tube you breath provides the heat needed for the reaction.

Generally iodine fuming, for practical reasons, is usually used for relatively small objects unless you have a fuming tank that you can use. You can use a fish tank (without water) and a small coffee cup warmer to make a fuming chamber. Place the coffee cup warmer in the tank along with the items to be fumed and then place some iodine crystals in a suitable container (plastic pop bottle lid) and set the container on top of the warmer plate. Seal the chamber and watch the object. Within a few minutes you will see the prints, if there are any, begin to develop.