Rapid-Set Instructions
1. Make an aluminum pattern 1½ % to 2 % larger, by volume, than the finished mold.
Except for this shrinkage allowance, the pattern should be an exact duplicate of the finished part.
2. Prepare an aluminum box with walls at least ¾" from all edges of the pattern, and at least ¾" higher than
the top of the pattern.
We recommend the use of aluminum for both the pattern and the box because it is non-porous, can be
readily worked, and takes a fine finish. You can also get good results with any non-porous material that
can withstand the curing cycle. Porous materials capable of absorbing or containing volatiles, such as
wood, can be used. However, the resultant Rapid-Set Mold will contain bubbles and imperfections, which
may or may not be carried over to the refractory
3. Preheat pattern and box in an oven at 100 oF for at least 15 minutes to prevent moisture from
condensing on the platform surface to cause air pockets.
4. Pour Rapid-Set slowly into box until it is completely full to overflowing. Try to avoid pouring directly on
the pattern surface to avoid air pockets, and let the liquid fill all undercuts, letters and details. Take care
to avoid spilling while transferring from workbench to oven.
5. Cover entire surface by slowly sliding an aluminum plate across top to allow even curing and a
flat surface to the mold.
6. Heat in oven set at 200 oF for ½ hour, then raise to approximately 320 oF. When proper curing
temperature has been reached, a slight trace of smoke will appear. Heat at this temperature for
one hour for every ½" of mold, measured at the thickest section. Where possible avoid an
air-circulating furnace or the Rapid-Set may become prematurely hardened. Undercured molds
will be soft, weak and easy to tear. The main cause of undercuring is too low a temperature.
Overcured molds (too high a temperature) will be much darker than original liquid and contain
many small bubbles.
7. Allow the box to cool after you remove it from the oven. Remove the now-solid Rapid-Set mold by
stripping it away from the pattern. The same pattern and box can be used to make innumerable molds.