The difference between fusible plaster mold and foaming plaster mold is discussedand an allaround suveying of the features of foaming plaster mold is made

and the facilities andmethods for permeability measuring are introduced. It is proposed that there are three criterionsfor evaluating the qualities of foaming agents. An ideal agent has been obtained by experiments.The relations among the agitating time

speed and foaming increament are established. Foamingplaster molds with foaming rate over 50%

with permeability up to 6 cm/min and compressivestrength up to 0. 8 MPa can be obtained according to the proposed technical regulations.