Lightning Powder Drierite Crystals (2 oz.) Iodine fuming is a method of developing latent prints on paper, cardboard, and many other paper surfaces. Iodine fuming should be used before Ninhydrin or Physical Developer (or other silver nitrate-type solution). Because it reacts to a different residue, it will not interfere with their subsequent application. This kit comes complete with carrying case, Iodine fuming apparatus, Drierite® crystals, glass wool, and Iodine crystals. Replacement items are available. Shelf-life of Iodine crystals: by keeping the jar tightly sealed, the Iodine will last for months. Once the jar is opened, the material will begin to sublimate (change from a solid into a gas without going through a liquid stage) immediately, so work quickly. This product is very corrosive and will rust many types of metals. Do not store it in a drawer with metal handles or fixtures.