The simplest solution to prepare is made by using a 25 gram jar of ninhydrin powder or crystals. Pour the entire jar of ninhydrin powder into the gallon container and stir until completely dissolved. The solution is ready for use and should last a month or two if kept out of light and away from heat. Instead, by using approximately the proportions given above, smaller amounts of solution may be prepared. Acetone dissolves most inks, and the writing on the check, threatening letter, or drug ledger may be completely washed out using this simple method.
Alcohols evaporate more slowly than acetone, and therefore the paper takes longer to dry.
Also, the alcohols do not have as strong an odor os acetone, and one is less apt to be aware of breathing hazardous fumes. Like acetone, alcohols dissolve ink. Acetone and alcohols are flammable, so care must be exercised in keeping these solutions away from any source of ignition. An alternate carrier has been sought for several years. The Police Scientific Development Branch of the Home Office, UK, recently found a suitable replacement formula using heptane.