Metal penetration or breakout presents as an irregular metal formation; typically in slots, holes, passages or tight areas. This defect indicates that the metal broke out,  or penetrated the ceramic shell. This is usually due to the fact that the shell is typically too weak (due to structure or dryness) to adequately hold the metal in the desired shape. This defect is often referred to as birdnesting when it appears in corners. 

The causes of this defect are evident in the shell and other portions of the process. To cure these causes, R&R recommends taking the following actions.