Plaster Craft FAQ

Commonly asked questions about leather working.

Q. How do I hang plaster wall pieces?

A. For all types of plaster hangings I use a piece of wire bent into the shape of the Greek letter Omega. As the plaster sets I position the leg portion into the plaster at an angle to create a hanging loop. Larger hangings should have 2 of these. For smaller hangings some folks like to drill a hole in the back to fit over a nail, but I find this does not work as well and increases the chance of cracking the plaster.

Q. Can I use your rubber molds for plaster?

A. Yes, they work well for plaster, but you will need to plug the wick hole with a small piece of wire or toothpick.

Q. Why am I having trouble demolding my latex molds?

A. Most of the time this is caused by failure to lubricate the outside of the mold before demolding. When ready to demold, dip the entire mold in water, then rub one drop of dishwashing liquid over the entire outside of the mold. The surface is now slippery enough to slide easily over itself. Failure to do this will normally result in a ruined mold.

Q. What is the life span of a latex mold?

A. If well cared for, the maximum life expectancy of latex molds is 40 to 50 castings. Molds with severe undercuts (i.e. that need to be stretched further) will generally not last as long as those without undercuts (such as a pyramid).

Q. Can I allow my castings to remain in the mold overnight?

A. You could, but it is not very good for latex molds. Other molds are less sensitive. Castings should be de molded as soon as hardened to minimize contact with the mold. Generally when the plaster gets hot to the touch it is ready for de molding.

Q. How do I clean latex molds?

A. Most media used for casting in latex molds (plaster, wax additives) are harmful to the latex. Immediately after use the mold should be washed with dishwashing liquid and water, then rinsed thoroughly.

Q. What is the best way to store my latex molds?


Q. Is there a way to improve the strength of my small castings?

A. If increased strength is needed, we suggest using Ultracal in place of plaster. It contains Portland cement and is far stronger, although a bit more expensive.

Q. Can I use plaster from the local building center?

A. Yes. That will work for most castings, although for castings that are fragile or that need to be stronger, Ultracal will work better.

Q. How can I correct a warped latex mold?

A. Warmth and pressure will return latex to its original shape. Fill the mold with hot (not boiling) water and suspend it. This may need to be repeated several times. The hot water warms the latex and the weight of the water eventually pushes it back to its original shape.

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Disclaimer: The information presented here is accurate to the best of my knowledge and common plaster crafting practices as of the time of this writing. These FAQ's are common questions asked our tech support department starting in 2000 and updated and rewritten in April 2012. The author and the publisher accept no liability for the use or misuse of any of the information presented these pages - they are presented for informational purposes and is used at your own risk.

Author: Bob Sherman

Publisher: Bobby's Craft Boutique Inc.

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