Plaster Casting 127 



This is the model, of which six copies are required. 



Take a sheet of brown paper or, better still, waxed paper 

 and fold it into a box, without cutting, by taking a piece/ 

 12" x 8", folding a long strip 2" wide down each side and 

 4" wide across each end. Then double up one edge and one 

 end, fold back the projecting corner behind the upper end, do 

 the same on the other side, and fold down the remaining 2'' 

 strip to hold all in place. Repeat at the other end. 2 If made 

 of waxed paper, the whole can be fixed by the application of 

 a hot knife-blade. Brown paper may need sealing-wax. 



Take about 500 c.c. of water in a basin or other wide-mouthed 

 vessel, and scatter into it two or three handfuls of superfine 

 plaster of Paris, stirring well with a steel spatula or similar flat 

 instrument. Continue adding the plaster until a thin creamy 

 mixture is obtained, when stirring should be discontinued. The 

 paper pyramid should now be well rubbed with oil, or melted 

 vaseline, and the surface smoothed down carefully. Pour the 

 mixed plaster into the box, and when almost full, press down 

 the model, base upwards, into the plaster, permitting it to rise 

 and fall several times in order to get rid of air-bubbles, and 

 finally hold it in position by placing two knitting-needles across 

 the box top, against which the model will float. (Hatpins are 

 very useful in this connection, as they may be inserted through 

 the side of the paper box.) Then fill in the plaster until it 

 shows a tendency to creep over the edges of the model and 

 run on to the base. Allow the box to remain untouched until 

 the plaster is quite hard overnight, if possible. 



At this stage the model may be removed a matter of little 

 or no difficulty in this case, as there are no undercuts, and the 

 paper will have become softened so that it will come away from 

 the plaster quite easily. The mould should be dried either by 

 standing in a warm, dry place, or in a water oven at 100 C. 



Having fined the corners down, and made any necessary 

 alterations to the mould in order to remove the effects of bad 



1 The size of the paper will vary with the size of the object. Boxes 

 of any shape and depth may easily be constructed on this plan. 



2 Boxes such as these, of good writing paper, will hold water while 

 it is boiled over a gas flame. 



