There are two defects in this category: hot tears and hot spots. Hot tears, also known as hot cracking,[20] are failures in the casting that occur as the casting cools. This happens because the metal is weak when it is hot and the residual stresses in the material can cause the casting to fail as it cools. Proper mold design prevents this type of defect.[3]
Hot spots are areas on the surface of casting that become very hard because they cooled more quickly than the surrounding material. This type of defect can be avoided by proper cooling practices or by changing the chemical composition of the metal.[3]