The Prop Builder's Molding & Casting Handbook

Metadata

• Author: Thurston James
• Full Title: The Prop Builder's Molding & Casting Handbook
• Category: #books

Highlights

• Casting plaster or plaster of Paris works easily and will set up in about twenty minutes. It is inexpensive and is easily available at lumber yards in 100 pound bags. (Location 363)
• No. 1 Pottery Plaster is formulated to be extra absorbent, and is therefore to be preferred on all operations where you are going to use the slip casting procedure. (Location 367)
• Hydra-Cal isn’t really a plaster, but more a kind of cement or mortar, much like dental stone. It sets up much harder than casting plaster, and will withstand repeated use. Because of its strength it also stands a better chance of retaining intricate detail that could break or chip if the casting were made in plaster. (Location 369)
• Colder water will slow the setting time; hot water will speed it up. Always sift the plaster into the water, and not the reverse. (Location 415)
• It is a good idea to dry large molds for a couple of days with the two halves strapped together. Molds can warp during cure-out, and clamping helps keep them registered to each other. (Location 463)
• Alginate, manufactured from a kind of seaweed, is the only really safe material for the casting of human body parts. (Location 535)
• Silicone RTV (room temperature vulcanizing) rubber is usually your best choice, when you are searching for a mold-making material. (Location 702)
• Silicone rubber molds will withstand high temperatures—high enough that you can pour melted picco resins (400°F.) into them. And that’s pretty hot. (Location 715)
• Study the face of your pattern to find its lowest depressions. A sprue should be drilled directly over each of these places to assure the injected rubber reaches the deep concavity and that no air pockets form. (Location 843)
• Drill one final hole in the apex of your mold. This is an air hole, which allows air to escape as you inject silicone into the lower sprues. (Location 846)
• However, now that you know how much is needed and you are not guessing, mix a little extra. Do not be stingy with your materials. If you don’t mix enough, the whole mold can be ruined, and there is no economy in that. (Location 859)
• Plaster molds are not recommended when you are casting with aggressively tenacious plastic materials. Silicone RTV molds are best, because they are flexible, give high resolution, and are naturally releasing. (Location 1011)
• Always make it a rule to cast a hard material (plaster, polyester resin, fiberglass, etc.) in a flexible or soft mold, to allow an easy release. (Location 1018)
• If you cannot perform the necessary steps safely, choose another material! (Location 1059)
• Absorption casting is a very old pottery-making technique in which liquid clay (called slip) is poured into a plaster mold. The dry plaster mold absorbs water from the liquid clay, building a fragile wall inside the mold. This wall remains behind when the clay is poured out. It is allowed to dry a little more, and then is removed from the mold and fired in a kiln to make a finished casting. (Location 1072)
• When you drop the pitcher, it will break. If the breakage seems to be too extensive, you can prepare the next pitcher with a coating of flex-glue before you break that one. This flexible coating will control some of the spatter. (Location 1166)
• Machinable wax melts, pours, and sets up just like candle wax. Since it sets up so hard, its uses in making molds and castings are obvious. (Location 1562)
• The flexing and stretching qualities of latex rubber make it especially difficult to color. Most paints sold commercially cannot expand and contract with the latex skin. They tend to form flakes and fall off. You can make a rubber-based paint yourself, however, that is very successful on latex. (Location 2033)
• Patterns made of thinner materials, such as unsupported Masonite or sheet metal, could easily collapse under the pressures of forming, but even these can be used when reinforced with internal bracing. (Location 2536)
• The cavity of a thin-shelled mold can be filled with Plasticine when only a few reproductions are required. Repeated castings, however, eventually transfer so much heat to the clay that it softens and loses its effectiveness as a reinforcement. Even this problem can be overcome if you have a refrigerator nearby. (Location 2560)
• You can form a releasing surface on urethane foam or clay molds by vacuum forming a skin of polystyrene directly over the original sculpture, melting it into the mold, and leaving it there. Vacuum formed polystyrene will not adhere to polystyrene. So the plastic jacket functions as a mold release for all future castings. (Location 2571)
• The “form” for a hemisphere is nothing more than a large plywood box, open on the bottom, with a large perfect circle cut into the top. (Location 2876)
• The plastic makes contact with the plywood face with the circular hole, and as the vacuum is applied, a perfect hemisphere is formed by the plastic being drawn into the interior of the box. (Location 2881)

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title: The Prop Builder's Molding & Casting Handbook longtitle: The Prop Builder's Molding & Casting Handbook author: Thurston James url: , source: kindle last_highlight: 2021-10-10 type: books tags:

The Prop Builder's Molding & Casting Handbook

Metadata

• Author: Thurston James
• Full Title: The Prop Builder's Molding & Casting Handbook
• Category: #books

Highlights

• Casting plaster or plaster of Paris works easily and will set up in about twenty minutes. It is inexpensive and is easily available at lumber yards in 100 pound bags. (Location 363)
• No. 1 Pottery Plaster is formulated to be extra absorbent, and is therefore to be preferred on all operations where you are going to use the slip casting procedure. (Location 367)
• Hydra-Cal isn’t really a plaster, but more a kind of cement or mortar, much like dental stone. It sets up much harder than casting plaster, and will withstand repeated use. Because of its strength it also stands a better chance of retaining intricate detail that could break or chip if the casting were made in plaster. (Location 369)
• Colder water will slow the setting time; hot water will speed it up. Always sift the plaster into the water, and not the reverse. (Location 415)
• It is a good idea to dry large molds for a couple of days with the two halves strapped together. Molds can warp during cure-out, and clamping helps keep them registered to each other. (Location 463)
• Alginate, manufactured from a kind of seaweed, is the only really safe material for the casting of human body parts. (Location 535)
• Silicone RTV (room temperature vulcanizing) rubber is usually your best choice, when you are searching for a mold-making material. (Location 702)
• Silicone rubber molds will withstand high temperatures—high enough that you can pour melted picco resins (400°F.) into them. And that’s pretty hot. (Location 715)
• Study the face of your pattern to find its lowest depressions. A sprue should be drilled directly over each of these places to assure the injected rubber reaches the deep concavity and that no air pockets form. (Location 843)
• Drill one final hole in the apex of your mold. This is an air hole, which allows air to escape as you inject silicone into the lower sprues. (Location 846)
• However, now that you know how much is needed and you are not guessing, mix a little extra. Do not be stingy with your materials. If you don’t mix enough, the whole mold can be ruined, and there is no economy in that. (Location 859)
• Plaster molds are not recommended when you are casting with aggressively tenacious plastic materials. Silicone RTV molds are best, because they are flexible, give high resolution, and are naturally releasing. (Location 1011)
• Always make it a rule to cast a hard material (plaster, polyester resin, fiberglass, etc.) in a flexible or soft mold, to allow an easy release. (Location 1018)
• If you cannot perform the necessary steps safely, choose another material! (Location 1059)
• Absorption casting is a very old pottery-making technique in which liquid clay (called slip) is poured into a plaster mold. The dry plaster mold absorbs water from the liquid clay, building a fragile wall inside the mold. This wall remains behind when the clay is poured out. It is allowed to dry a little more, and then is removed from the mold and fired in a kiln to make a finished casting. (Location 1072)
• When you drop the pitcher, it will break. If the breakage seems to be too extensive, you can prepare the next pitcher with a coating of flex-glue before you break that one. This flexible coating will control some of the spatter. (Location 1166)
• Machinable wax melts, pours, and sets up just like candle wax. Since it sets up so hard, its uses in making molds and castings are obvious. (Location 1562)
• The flexing and stretching qualities of latex rubber make it especially difficult to color. Most paints sold commercially cannot expand and contract with the latex skin. They tend to form flakes and fall off. You can make a rubber-based paint yourself, however, that is very successful on latex. (Location 2033)
• Patterns made of thinner materials, such as unsupported Masonite or sheet metal, could easily collapse under the pressures of forming, but even these can be used when reinforced with internal bracing. (Location 2536)
• The cavity of a thin-shelled mold can be filled with Plasticine when only a few reproductions are required. Repeated castings, however, eventually transfer so much heat to the clay that it softens and loses its effectiveness as a reinforcement. Even this problem can be overcome if you have a refrigerator nearby. (Location 2560)
• You can form a releasing surface on urethane foam or clay molds by vacuum forming a skin of polystyrene directly over the original sculpture, melting it into the mold, and leaving it there. Vacuum formed polystyrene will not adhere to polystyrene. So the plastic jacket functions as a mold release for all future castings. (Location 2571)
• The “form” for a hemisphere is nothing more than a large plywood box, open on the bottom, with a large perfect circle cut into the top. (Location 2876)
• The plastic makes contact with the plywood face with the circular hole, and as the vacuum is applied, a perfect hemisphere is formed by the plastic being drawn into the interior of the box. (Location 2881)