A riser is a reservoir of material built into the mold to prevent porosity resulting
from shrinkage.
It prevents porosity by providing molten metal to the casting as it solidifies, so that
porosity forms in the riser and not the casting. After solidification, the riser is
removed and the part is free of porosity. Figure 1. Example of a Riser Positioned in Relation to the Part and Pouring Cup
