How to Cast a Rubber Latex Mold

Simple shapes can be reproduced with a rubber mold.

Latex molding rubber is available at most hobby shops and is an ideal material for making simple molds. It produces a flexible mold that can be used to make many duplicates of the original object. While the latex is flexible, it is strong enough to hold its shape when cast over small objects such as rocks and toys. The dip mold method is ideal for longer shapes such as candles and action figures, while brush-up molds work well for larger objects such as rocks and toy cars.

Things You'll Need

• Clay
• Spray enamel
• Latex rubber
• Screw (optional)
• Wax paper
• Dish soap
• Paintbrush
• Hairdryer (optional)
• Cheesecloth

Instructions

Preparing the Object

1. 

   The space between this toy's legs should be filled with clay.

   Fill in any holes that pass all the way through the object to be molded with a thin wall of clay. This will prevent the latex mold from locking onto the object. The resulting solid wall in your duplicates will be cut away with a knife.

2. Spray two thin coats of spray enamel onto objects made of porous materials such as plaster and foam. This sealant will prevent the latex from seeping into the object and bonding to it.

3. Allow the sealant to dry completely.

Dip Molds

1. Hold the object by its base. If possible, insert a small screw into the base to use as a handle.

2. Dip the object into a jar of molding latex. Do not cover the bottom of the base.

3. Hang the object over a sheet of wax paper to allow the latex to dry. This may take several hours. Excess latex will drip onto the paper.

4. Dip the object into the latex two more times, letting each coat dry completely.

5. Rub dish soap onto the outside of the mold, then peel it off of the object like a glove. The soap will act like a lubricant, allowing the rubber to slide against itself.

Brush-Up Molds

1. Brush a thin layer of latex onto the object with a cheap paintbrush.

2. Allow the latex to dry. A hairdryer can be used to speed this process.

3. Brush an additional eight to ten layers onto the object.

4. Press squares of cheesecloth into the wet final layer, then add more latex and allow it to dry. This will give the mold additional strength.

5. Peel the mold off of the object.

References

• Model Train: Latex Mold Making
• "The Prop Builder's Molding & Casting Handbook"; Thurston James; 1989