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A kneaded eraser, also commonly known as a putty rubber, is a pliable erasing tool used by artists. It is usually made of a grey or white unvulcanized rubber (though it can be found in many different colors, such as green , blue , hot pink , yellow , and so forth) resembling putty or chewing gum.
Kneader eraser. Erasing is often performed with a kneaded rubber eraser. This is a malleable eraser that is often claimed to be self-cleaning. It can be shaped by kneading it softly with hands, into tips for smaller areas or flipped inside out to clean. Other erasing tools that are often used with charcoal are electrical erasers and pencil erasers.
A silicone mold generally requires little or no mold-release or surface preparation, as most materials do not adhere to silicone. For experimental uses, ordinary one-part silicone can be used to make molds or to mold into shapes. If needed, common vegetable cooking oils or petroleum jelly can be used on mating surfaces as a mold-release agent. [22]
The core of the balls are formed by compression molding with chemical reactions. First, polybutadiene is mixed with additives, then extruded, pressed using a calender and cut into pieces which are placed in a mold. The mold is subjected to high pressure and high temperature for about 30 minutes, enough time to vulcanize the material.
Silicones are usually very thick (high viscosity), and must be vacuum degassed prior to pouring, to minimize bubble entrapment. If making a brush-on rubber mold, the curing time factor between coats is long (longer than urethanes or polysulfides, shorter than latex). Silicone components (A+B) must be mixed accurately by weight (scale required ...
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Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, while heat and pressure are maintained until the molding material has cured; this process is known as compression molding ...