Now, next make a thick, creamy mixture of plaster of paris by sifting the plaster gradually into the water, stirring constantly to prevent lumping. Let this stand a few minutes to allow the air bubbles to escape. Pour mixture slowly over pattern in this box to about double the thickness of the pattern. Allow several hours to dry, then remove. If the stearine or sweet oil was applied properly, this will be easy.
Mold is now ready for use.
First and foremost always make sure that you have lubricated your mold with beeswax or stearine. Place molds on a reasonably level surface and pour the sulpho-plastic into the mold, quickly and smoothly. Do not pour from a height as this will break the lubricant and leaves blemishes on the casting. Plastic must be poured quickly to prevent cooling in folds and thus making a poor casting. One of the big assets of sulpho-plastics is the fact that it dries and hardens almost immediately.