Blowholes are internal or surface voids formed when gas from the molten metal or the mold cannot escape before the metal freezes. They appear as smooth, rounded bubbles, unlike the jagged cavities caused by shrinkage. They severely weaken the casting and often require scrapping the part.
Heard on the job
We lost three engine blocks to blowholes because the sand in the cope was too wet.
Also heard as
- gas porosity