Making Garden Stone Molds


BRUSH ON METHOD USING URETHANE AND A MOTHER MOLD

Choosing a Model

Choosing the model for this method is the same as for a poured mold with no mother mold. In this example I am using a small trivet made of cement. It sits less than an inch tall and is about 4 inches in diameter. The trivet is secured to the bottom of the baseboard with silicone caulk. The model will be covered with two thin layers of two part urethane molding compound. Since the two layers will be very flimsy a mother mold will be poured to support the new mold. This method produces very inexpensive molds. The dolphin mold in the previous example used about $60 worth of urethane. Had it been done using this method the cost would have been closer to $10 including the mother mold.



Secure the model to the bottom of the baseboard with silicone and spray it with a release agent.






Apply a Release agent

Apply a release agent to the model before coating it with the urethane. A mixture of 10% castor oil and 90% alcohol will work or there are many silicone and soap based releases available.


Brush on molding compound

For this example we are using two thin coats of the urethane molding compound.


Brush on the first coat also called the detail coat and let it dry. Let the first coat of urethane set for about 30 minutes and apply the second coat. Two coats were used for this mold but more can be applied. The more coats the stiffer the mold will be.

Build the containment frame

After the coats of urethane have set up completely (24 hours) a containment frame is built around the model.


Containment frame built with coreplast

Spray the coated model and containment with a release agent

After the containment frame is constructed the inside and the coated model are coated with a release agent so that the plaster mother mold will not adhere to the mold.


Spray with a release

Mix your plaster, pour it and let it set


Mix plaster of paris



Pour over model covering it with about a half inch of plaster.


Let is set up (about 30 minutes)
Remove from the Containment frame and from urethane mold


Remove the walls



Pull the urethane mold away from the new mother mold


Remove the model from the urethane mold



Lay the mold into the mother mold and you are ready to pour castings



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