Category:Molding and Casting

Contributors: Sutton Hastman

Molds and Casting

Mold- negative space used to produce a cast

Cast- positive replica of the original object

Release Agents and Barriers

Used to protect objects when casting directly on the object or to help remove casting from the mold material

·       Plastic wrap

·       Vaseline

·       Talc or Cream of Tartar

·       Teflon tape (can use a brush to work into crevices)

Mold Making Materials

Plaster: Exothermic. Can be used to support flexible molds such as silicone molds

Aluminum foil: can be used as a flexible mold material.

Wax: Good for simple shapes. Requires gentle heat and pressure to shape; therefore it may not be suitable to use directly on some objects. Wax can be melted and bushed over the object to create a mold, but be cautious of heat sensitive materials. Lost wax casting.

Clay: Available as hard setting or workable clays. Clay can be used as the mold material or to seal box molds. It is important to use sulfur-free clay if working with silicones, otherwise the sulfur prevents the silicone from setting. Some common clays used include: Sculpy clay and Klean Klay.

Silicone: Some silicone materials may be exothermic. Tend to be more costly than other materials.

·       OOMOO Silicone Rubbers: Tin cure silicone compounds that are one-to-one by volume mix ratios. Good for two-piece molds. Store at room temp.

·      OOMOO 25 has a 75-minute cure time.

·      OOMOO 30 has 6 hour cure time.

Pour casting

·       Zhermack Elite HD+ Putty Soft, regular set: A two-part silicone impression putty. Quick set. Store in fridge.

Casting Materials:

Plaster: Good for fine details. It can be brittle. There may be slight dimensional change to the cast. Low cost material.

Wax: Can be the casted material or used in Lost wax casting. Can be brittle.

HXTAL NYL-1: For thicker casts, it is best to build up in thin layers and allow the HXTAL to cure for 5-7 days between layers. HXTAL may take on the texture of the mold material and have a matte surface; however a thin coating of HXTAL can be applied after casting to add gloss to the surface.

Paraloid B-72: Best if cast into thin sheets to avoid bubbles. Sheets can be cut, heated, and shaped.