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Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO 4 ·2H 2 O. [4] It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk chalk.
Beading or bead: Moulding in the form of a row of half spherical beads, larger than pearling Other forms: Bead and leaf, bead and reel, bead and spindle Beak : Small fillet moulding left on the edge of a larmier , which forms a canal, and makes a kind of pendant . [ 1 ]
Drywall (also called plasterboard, dry lining, [1] wallboard, sheet rock, gib board, gypsum board, buster board, turtles board, slap board, custard board, gypsum panel and gyprock) is a panel made of calcium sulfate dihydrate , with or without additives, typically extruded between thick sheets of facer and backer paper, used in the construction ...
The rounded bead here was made with a scratch stock rather than the more common beading plane or router bit. A bead is a woodworking decorative treatment applied to various elements of wooden furniture, boxes and other items. A bead is typically a rounded shape cut into a square edge to soften the edge and provide some protection against splitting.
Lath and plaster largely fell out of favour in the U.K. after the introduction of plasterboard in the 1930s. [2] In Canada and the United States, wood lath and plaster remained in use until the process was replaced by transitional methods followed by drywall (the North American term for plasterboard) in the mid-twentieth century. [citation needed]
A selection of glass beads Merovingian bead Trade beads, 18th century Trade beads, 18th century. A bead is a small, decorative object that is formed in a variety of shapes and sizes of a material such as stone, bone, shell, glass, plastic, wood, or pearl and with a small hole for threading or stringing. Beads range in size from under 1 ...
Two principal techniques are used to produce seed beads: the wound method and the drawn method. The wound method is the more-traditional technique, is more time-consuming, and is no longer used in modern bead production: in this technique, a chunk of glass known in glassmaking as a gather and composed mainly of silica is heated on an iron bar until molten.
Autoclave expansion is the most common route the bead foam. [4] Butane or pentane is often used as a blowing agent (before 1992 CFCs may have been used). Depending on the specific process uses the beads may be cross-linked either by electron beam irradiation (see Electron beam processing), or by the addition of a chemical agent such as dicumyl ...