AbstractFrom literature it appears that simple saturated triglycerides and commercial fats contract to a considerable extent when they undergo transformation from liquid to solid state and from an instable to a more stable crystalline form. In spite of these facts, the simple saturated even triglycerides and some fully hydrogenated fats exhibit violent solidification expansion by voluntary cooling. Solidification experiments carried out with several saturated even triglycerides and fats under various solidification conditions have shown that the solidification expansion tendency depends upon the chemical composition of the fat, as well as on the solidification conditions. The solidification expansion tendency is increased by various more or less independent factors, namely decreasing iodine value, increasing fatty acid and triglyceride uniformity, increasing triglyceride symmetry, increasing tendency to rapid formation of the stable β crystals, seeding with β crystals, voluntary cooling, moderate cooling velocity, and increasing bulk amount of fat. All the expanded solidified fats ended up being in the β crystalline form, whereas the nonexpanded fats ended up with the β’ form. The solidification expansion is avoidable by careful control of the cooling procedure.