Early in its history, liquid nitroglycerin was found to be "desensitized" by cooling it to about . At this temperature, nitroglycerin freezes, contracting upon solidification. Thawing it out can be extremely sensitizing, especially if impurities are present or the warming is too rapid. Chemically "desensitizing" nitroglycerin is possible to a point where it can be considered about as "safe" as modern high explosives, such as by the addition of roughly 10 to 30% ethanol, acetone, or dinitrotoluene (the percentage varies with the desensitizing agent used). Desensitization requires extra effort to reconstitute the "pure" product. Failing this, desensitized nitroglycerin must be assumed to be substantially more difficult to detonate, possibly rendering it useless as an explosive for practical application.