AbstractCocoa butter and other confectionery fats do not behave alike on molding. Explanations for the behavior of cocoa butter generally are unavailable. The linear contraction of molded cocoa butter on solidification under various conditions was determined. Maximum linear contraction of about 2% was measured when a well‐seeded sample was solidified at 16C. Nearly all of this contraction occurred during the first half hour. A theoretical explanation for this contraction was developed. Linear contraction takes place after the well‐seeded cocoa butter has solidified in the next‐to‐highest melting form and while this solid form is transforming to the most stable polymorph. Addition information was developed on the polymorphic forms of cocoa butter, the permanence of seed crystals at various temps, rates of solidification, and solidification characteristics of unseeded cocoa butter. The data were obtained by dilatometric examination of a small sample using a volumetric dilatometer and direct measurement of linear contraction during solidification in a mold.