www.smooth-on.com to see more video tutorials and image galleries. Examining the different types of RTV mold rubber available for mold making and casting from Smooth-On. Advantages of Latex * Least expensive mold rubber available. * Very elastic, thin-walled and strong. * Lasts a long time. * Offers good abrasion resistance. * Good for making glove molds. Disadvantages of Latex * Strong ammonia smell. * Can only be brushed onto an original. * Many coats are necessary. * Can take up to two weeks to make mold. * Shrinkage. Casting with Latex * Good for casting concrete, wax or plaster. * Generally not used for casting urethane, polyester, or epoxy resins, or low-temp metal alloys. Advantages of Polysulfide * Soft, stretchy, and durable. * Last a very long time. * Moderate cost. * Will cure against water clay or clays containing sulfur. Disadvantages of Polysulfide * Accurate gram scale to weigh components. * Offensive odor. * May stain white plaster during casting. Casting with Polysulfide * Good for casting plaster or wax only. * Will not handle concrete, resins, or low-temp metal alloys. Advantages of Silicone Rubber * Best release properties of all the mold rubbers. * Model surface preparation minimal nor not necessary. * Release agent for casting often not necessary. * Most heat resistance to high temperatures. * Can cast low-tempmetal alloys such as tin and pewter. * High tear resistance. * Knotty tear propagation. * Very good chemical resistance. * Longest mold life …