What is the name of a hole formed during solidification due to escaping gases?

• A. A blow hole
• B. A burst
• C. A cold shut
• D. Flaking

Answer: (A)

Gas porosity forms holes during solidification when dissolved gases escape but become trapped as the metal freezes. As the molten metal cools, gases like hydrogen come out of solution; if venting or flow isn’t adequate, these gas pockets stay in the solid as cavities. This specific defect is called a blow hole. Other defects have different causes—cold shuts are from two metal fronts not fusing properly, bursts refer to different rupture issues, and flaking is a surface fracture or spall—so they don’t describe holes formed by escaping gas during solidification.