Buckling presents as a pyramid-like bump or lump (usually with a sharp peak) that appears on the surface of the casting. This defect indicates that the shell shrinks and loses adhesion to the wax pattern and buckles outward during the drying process. This is especially prevalent on primary coats and flat surfaces; indicating that the primary coat moved away from the wax pattern. 

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