Glossary A-CC-CD-EF-GG-II-MN-PP-SS-SS-TT-VW Aging a change in the molecular structure of an alloy occurring over a period of time following casting. The properties and dimensions are affected. Heating accelerates aging. Blister a surface bubble caused by gas expansion which was trapped within the die casting. Blow holes voids or pores which may occur due to entrapped air or shrinkage during solidification of heavy sections. Box that part of the die attached to the die casting machine and containing the ejector plate or core plate or both. Cavity the recess or impressions in a die in which the casting is formed.