a disintegrative member , such as a salt core , is provided with a vent opening extending through its thickness from an outer surface to an inner surface in order to allow gases to pass radially inwardly through the body of the salt core and away from a region proximate the salt core &# 39 ; s outer surface . the escape of these gases through the vent opening decreases the likelihood that porosity will be formed as a result of those gases being trapped in a region proximate the outer surface of the salt core because the molten metal solidifies more slowly in this area because of the thermal insulative qualities of the disintegrative member .