Recrystallization is used to increase the purity of a substance. Filtration and drying are part of this procedure. The substance is dissolved in an appropriate solvent and then caused to recrystallize, while hopefully leaving the impurities behind in solution. Once the substance is crystallized and in solid form, it is filtered and dried. Factors influencing this entire procedure include the appropriate solvent, temperature and filtration technique. Sufficient drying is also required in order to remove any trace of solvent.