Hydraulic cement, the most popular of both classifications, is the most favoured material due to the fact that it is easily workable and dries quickly.  The ingredients—a mixture of limestone, clay and gypsum—are combined at high temperatures to manufacture a product that sets and hardens rapidly. While the first form of cement invented was non-hydraulic, it is not as practical or convenient for most applications.  This type of cement includes lime, gypsum plasters and oxychloride, which means that it does not set when exposed to water like hydraulic cement. In fact, this kind of cement needs dry conditions to set at all.