There are two defects in this category: hot tears and hot spots. Hot tears, also known as , 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 mould design prevents this type of defect.
Hot spots are sections of casting which have cooled down more slowly than the surrounding material due to higher volume than its surrounding. This causes abnormal shrinkage in this region, which can lead to porosity and cracks.  This type of defect can be avoided by proper cooling practices or by changing the chemical composition of the metal. 
Additional methods of minimising hot tears are not overheating the casting material and increasing the temperature of the mould.