SMALL IMPURE CRYSTALS WILL FORM if the filtrate solution is cooled too rapidly.
Recrystallization is a technique used to purify solid compounds. Solids tend to be more soluble in hot liquids than in cold liquids. During recrystallization, an impure solid compound is dissolved in a hot liquid until the solution is saturated, and then the liquid is allowed to cool. The compound should then form relatively pure crystals. Ideally, any impurities that are present will remain in the solution and will not be incorporated into the growing crystals.
HENCE, THE FORMATION OF SMALL IMPURE CRYSTALS.