I am trying to slip cast a large form that is about 2.5 ft tall and 1.5 ft wide at its widest point. The slip is being drained by sucking out the excess, but when removing the form, one side usually caves in. I figure this is just from uneven pressure in the drying process and the weight of the shoulders on the form. I heard about a technique where pressure can be put into the mold after removing the excess slip so the walls stay pressed against the plaster.Does anyone have more info on this technique, such as how much pressure (in terms of psi)/ how long pressure should be applied, and how to successfully close off the pour hole so there is no air escaping? Thanks in advance!