Metal Penetration

Technical Support

Struggling with a specific casting defect or just need general technical support?

  • Irregular metal formation; typically in slots, holes, passages or tight areas

  • Indicates that the metal broke out, or penetrated the ceramic shell

  • 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

  • Often referred to as birdnesting when it appears in corners

Causes of this defect are evident in the shell and other portions of the process; to cure, R&R recommends taking the following actions:


Weak spots in the ceramic shell due to difficulty of buildup in details.

Use thinner coats to strengthen detail. Consider using ceramic core material or preformed core to build deep pockets or slots.

Improper shell build in the detail area.

Use prewet, intermediate slurries and finer stuccos until the detail is adequately built.

Insufficient or poor shell drying.

Allow extra dry time on these parts, especially during early shell coats.

Excess slurry and/or stucco left behind.

Improve draining and/or blow off excess stucco between coats.


Rapid depressurization of autoclave.

Depressurize from maximum pressure to atmospheric gradually over about 2 minutes (evaluate autoclave operating parameters).

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