Method of producing castings or other mouldings by means of vacuum suction of flexible containers holding granular material

In a method of making a contoured mold member corresponding in shape to contours of a model, the steps comprising:

• a. forming a first air-tight chamber by sealing a readily deformable, flexible and extensible member about a peripheral edge of a container wall, said member including a portion extending beyond confines of said container;
• b. placing a model, contours of which are to be reproduced, against said extensible member and causing said extensible member to be partially conformed to said contours;
• c. introducing granular material into said chamber through a conduit thereto and causing said member to be conformed further to said contours;
• d. evacuating fluid at least partially from said first chamber creating a partial vacuum therein and causing said granular material to stiffen into a persistent shape and causing said extensible member to conform further to said contours;
• e. while maintaining said partial vacuum removing said model from contact with said extensible member thereby exposing a surface of said extensible member conformed to said contours of said model, said surface defining a mold cavity;
• f. filling said cavity with other granular material;
• g. sealing portions of said member, extending beyond confines of said container, to form a second air-tight chamber about said other granular material;
• and
• h. evacuating fluid from said second chamber to form a positive mold member from said other granular material and said extensible member.