G. (gauget mortar - gypsum plaster)

Gauged mortar - 1. Mortar made of cement, sand, and lime in specific proportions.  2. Any plastering mortar that is mixed with plaster of Paris to hasten setting. 
RS Means Building Glossary (undated)

Gauged skim coat -  A mixture of gauging plaster and lime putty applied very thinly as a final  coat in plastering. The mixture is trowelled to produce a smooth, hard finish. 
RS Means Building Glossary (undated)

Gauged stuff -  1. A mixture of lime putty and gypsum plaster that is used as a finish coat in plastering.  2. Gauged mortar. 
RS Means Building Glossary (undated)

Gauging plaster - A finish plaster coat prepared from lime putty mixed with about 35% gypsum plaster, producing a quick-drying finish coat.
Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated)

Gelatin - A mixture of proteins prepared by hydrolysing, via boiling, collagen obtained from skin, ligaments and tendons. Gelatin is composed of amino acids in the following proportions: glycine (25.5%), proline (18.0%), hydroxyproline (14.1%), glutamic acid (11.4%), alanine (8.7%) along with small amounts of arginine, leucine and aspartic acid. Gelatin is approved as a food product. Its production differs from that of animal glue in that raw materials are selected, cleaned and treated with special care so that the product is cleaner and purer than glue. Gelatin is strongly hydrophilic. In cold water, dried gelatin can absorb up to ten times its weight of water, forming a viscous mass. Adding alum to gelatin produces a harder gel. Potassium chrome alum and formaldehyde (formogelatin) also harden gelatin and make it insoluble. Gelatin is used for sizing and adhesive. It is mentioned as one of the organic additives used for stucco marble preparation according to literature.
Synonyms: gelatine; glue
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Gesso - A hard, white ground layer primarily used for tempera painting and water gilding. As the Italian word for gypsum, the term gesso was applied to ground layers prepared from gypsum and animal glue. Gesso grounds were used since medieval times in Europe. They were often applied in multiple layers with the initial gesso layer containing coarse gypsum particles (gesso grosso) and the final layer containing fine gypsum particles (gesso sottile). The dried surface was polished to an ivory-like finish. Because it was hard and inflexible, gesso was usually applied to a rigid support, such as a panel, picture frame or sculpture. From Renaissance times, a hard gesso prepared from calcium carbonate (chalk) in glue was used in northern Europe for oil and casein paintings. More recent formulations for gesso use synthetic binders and with one or more white pigments such as chalk, zinc oxide and titanium dioxide (about 10% for opacity).
Synonyms: gesso grosso; gesso sottile
Museum of Fine Arts, Boston (2000)

Gesso, glue - See gesso
Museum of Fine Arts, Boston (2000)

Glue - A strong, liquid adhesive originally made from animal protein. Now the term 'glue' is generally used for any type of adhesive, especially water-based formulations.  Animal glue has been made from ancient times by boiling animal hides, tendons, bones and hooves in water. The collagen is hydrolysed to form a semitransparent gelatin. Animal glues are applied hot and bind on cooling to form a strong, flexible and water-resistant join. Often glycerin or sorbitol is added as a plasticizer and phenols are added as preservatives to minimise biological growth. Top-quality animal glues are made from rabbitskin, sturgeon bladders and parchment clippings. Animal glue is mentioned as one of the main ingredients of stucco marble, more specifically as a binding medium. Several types of glue (fish, skin, rabbit skin, bone, horn glue and gelatine) are listed as organic additives for stucco marble preparation according to literature. 
Synonyms: animal glue; adhesive; gum; mucilage; gelatin; size; isinglass; fish glue; bone glue; parchment glue; Cologne glue; calfskin glue; nikawa; hide glue; rabbitskin glue; sturgeon glue
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Green earth - A natural earth pigment composed of iron silicate clays. Green earth pigments have been used since ancient times. They were ground from available earth minerals, such as celadonite, glauconite, cronstedtite and chlorite. The colour of green earth can range from yellow-green to sea-green to greenish-grey. In general, green earth is translucent in oils with moderate tinting strength and poor hiding power. It is a permanent, stable pigment that is compatible with all media. Green earth, or terre verte, is sometimes imitated by mixtures of Naples yellow and Prussian blue. It is listed among the pigments used for colouring stucco marble in the nineteenth and twentieth century.
Synonyms: terre verte (Fr.); terra verde (It.); tierra verda (Sp.); grune Erde (Ger.); creta viridis; celadon; Veronese earth; Belgian earth; Hessian earth; Tyrolean earth; Bohemian earth; Saxon earth; green stone; Theodotion; prasina; holly green; green stone; verdetta; Pigment Green 23; CI 77009; aegirin; celadonite, glauconite, cronstedtite; chlorite
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Ground - A foundation layer used to prepare a support material for the application of paint. Grounds provide a smooth, uniform, and nonporous surface. They can also act as a separating and stabilising layer to minimise environmental distortions or support deterioration due to reactions with the paint.  For artist paintings, grounds typically fall into these categories. 
1. Gesso or chalk - a glue binder mixed with gypsum or chalk  2. Emulsion -a glue medium emulsified with some oil, egg or resin  3. Oil ground- a drying oil, such as linseed oil, with lead white or other white pigment  4. Synthetic - acrylic or alkyd based primer introduced in the late 20th  century. For gilding, bole is used as a coloured ground or priming layer. Bole is typically composed of a red or brown clay. 
Synonyms: grounds; primer; gesso
Museum of Fine Arts, Boston (2000)

Grout - A liquid mixture of cement and sand or cement alone.
Powys (1929, reprinted 1981)

Guattaris marble - Patented in the 19th century, this is an artificial stone made by treating blocks of the anhydrite form of gypsum with chemicals such as sodium and calcium silicate to harden them. They are heated to a high temperature and the material crushed to a powder known commercially as marmorite. This can be mixed with water to make moulded ornament; pigments could be added to marmorite to produce coloured casts. See also : artificial stone.
Trench (2000)

Gum - Carbohydrate based containing exudates obtained from some trees or shrubs which are insoluble in alcohol and either soluble or swellable in water. Some gums, such as, agar, funori and carrageenan, are extracts from seaweed. Gums are used as adhesives, paint binders and sizes. The word 'gum' has also been commonly used to refer to any plant exudate. See also: gum arabic, gum tragacanth, cherry gum, plum gum, almond gum, bata gum, morocco gum, khair gum, karachi gum, cape gum, gum mamrah, cashew gum, semla gum, carob tree gum, guaic, chitin, napal, chicle, keetha gum, khaya gum, mesquite gum, cholla gum, soap berry gum, tartar gum, tandra gum, orange gum, grapefruit gum, neem gum, sapote gum, drum stick gum, lemon gum, agar, locust bean gum, xanthan gum, carrageenan, funori, seaweed glue, guar, ormocarpum, Joshua tree gum, spinifex gum, leopard tree gum
Synonyms: Gums
Museum of Fine Arts, Boston (2000)

Gum arabic - A water soluble gum commonly used in binding media of paints. Gum arabic is the amorphous exudate from the stem of several species of Acacia trees, especially Acacia senegal, found in tropical and subtropical areas of the world. Most gum arabic coming from the sub-Sahara region in Africa. Gum arabic contains arabinose, galactose, rhamnose, and glucuronic acid. It is sold in the form of round lumps, granules, thin flakes or as a powder; all of which may be white or slightly yellowish. Gum arabic is completely soluble in hot and cold water, yielding a viscous solution. However, heating a gum arabic solution to the boiling point will cause it to darken and will change its adhesion properties. Solutions of gum arabic will precipitate or gel with the addition of ferric salts, borax, alcohol, or sodium silicate. Gum arabic is used in watercolour paints. It is listed as an organic additive for stucco marble preparation according to literature.
Synonyms: gum arabicum; kordofan; picked turkey; white sennar; senegal gum; ghezineh gum; gomme blonde; gomme blanche; gum acacia, East India gum; kami; wattle gum
Wittenburg (1999); Museum of Fine Arts, Boston (2000)

Gypsum CaSO₄.2H₂O  - Gypsum (calcium sulphate dihydrate) is the product found in any gypsum mass after setting.  However, with regard to the basic material used for preparation, a large range of calcium sulphate phases in different stages of hydration and of different habitus has to be considered, depending on petrographic nature of the raw material and the way it is burnt.  References to the exact temperature of calcination vary among different authors, between 107°C and up to 400°C for scagliola.  In the seventeenth century, a special variety of gypsum, selenite or sericolite, burnt at 300°C, was used, while the currently used kind is gypsum calcined at 130° to 170°C.  At this temperature, the hemihydrate is formed.  According to the degree of purity and other factors, this hemihydrate is the major constituent of both plaster of Paris and alabaster gypsum. Some authors mention special procedures used for burning gypsum.  For example, the technique based on the immersion of gypsum into sulphuric acid, drying and then calcinating again produces the so-called gypsum marble.  Alum-gypsum, on the other hand, is a mixture of CaSO₄ with alum ? i.e. plaster of Paris soaked with alum solution, then burnt again and finely ground.  After setting, it obtains high mechanical strength and hardness.  According to Leixner, alum-gypsum, also called marble-gypsum, has been primarily used up to the 1960ís. Gypsum is also the main component of gypsum cements, such as Keeneís cement and Martinís cement. The mineral gypsum is also found naturally; it is  soft, transparent and easily cleaved. Massive blocks of fine-grained white, translucent gypsum are called alabaster and have been used since ancient times for carved ornamental objects and statuary. Gypsum is a commonly found mineral associated with sedimentary rock and deposits from seas, lakes and volcanic springs (gypcrete). For a long time, gypsum quarries in the Montmartre district of Paris supplied the starting material for the burnt gypsum that was, and still is, called plaster of Paris. Raw gypsum is used for carvings (alabaster), for wallboards (Sheetrock), as a paint pigment (terra alba) and as an ingredient in Portland cement. Its principal use is to manufacture gypsum plaster.
Synonyms: native calcium sulphate; alabaster; selenite; terra alba; satinite; mineral white; satin spar; light spar; sulphate of lime; puritan filler; crown filler
Wittenburg (1999);  Leixner (1993); Trench (2000); Museum of Fine Arts, Boston (2000)

Gypsum board - A type of wallboard with a plaster core sandwiched between two layers of paper. Gypsum board was patented in 1894 by Augustine Sackett. By World War I, production methods for gypsum board were standardised and it was widely used for the construction of military barracks. Over time, various fillers were added to decrease weight (pumice, bubbles, etc.), to increase fire resistance (asbestos) and to increase crack resistance (wood and mineral fibres). Dextrin, or starch, is typically used as a binder. Gypsum board, also called drywall, is fire resistant, dimensionally stable and inexpensive. During World War II, gypsum board completely replaced the use of metal lath/plaster walls in new construction because the prefabricated boards were faster to assemble and because the use of steel was restricted. Currently, it has widespread use in the construction of interior walls and ceilings.
Synonyms: plasterboard; plaster board; wallboard; drywall; Sheetrock® [U.S.Gypsum]; Gypsite; Sackett Board; Samson Plaster Board; Adamant; Bestwall Firestop; Gold Bond; Rocklath; rock lath
 Museum of Fine Arts, Boston (2000)

Gypsum cement -  A group of cements that are produced from calcined gypsum (plaster). Gypsum cement is also called gypsum concrete. Many various formulations are used. Some contain sand, hair or straw as extenders and many may contain small amounts of salts (potassium sulphate) as accelerants. Organic materials (blood, glue, casein) and weak acids (citric acid, boric acid) can act as retardants. -Keene's cement - plaster mixed with alum or aluminium sulphate. -Mack's cement - plaster mixed with sodium or potassium sulphate. -Martin's cement - plaster mixed with potassium carbonate. -Parian cement - plaster mixed with borax. -Scott's cement - plaster mixed with lime. -Spence's plaster- plaster mixed with Portland cement, sand, aluminium sulphate.
Synonyms: gypsum plaster; gypsum concrete; plaster of Paris; Keene's cement; Parian cement; Martin's cement; Mack's cement; Scott's cement; Spence's plaster
Museum of Fine Arts, Boston (2000)

Gypsum mortar -  An early mortar used in ancient Egypt for limestone construction (Lucas and Harris 1962). The gypsum was burnt and slaked then applied in thin layers between the heavy stones.
Museum of Fine Arts, Boston (2000)

Gypsum plaster - A type of plaster composed of calcium sulphate hemihydrate. Gypsum plaster was known to the ancient Egyptians and Mesopotamians and has been used for renders and mortars. It is also used for moulds, sculptures and castings. It is prepared by heating gypsum (calcium sulphate dihydrate) to partially remove the chemically bound water, thus producing calcium sulphate hemihydrate. When gypsum plaster is mixed with water, it converts to the hydrated calcium sulphate which rapidly sets to an impenetrable solid. It generates heat with setting and may expand slightly. Its rapid setting necessitates great skill in handling when used as a wall plaster. The set and workability of gypsum plaster are controlled by various additives. When mixed with aggregate and water, the resulting mixture is used for base-coat plaster. As it is slightly water soluble, its use in temperate climates was largely confined to interior decoration, as a finish for walls and ceilings, although it was occasionally used, on its own or mixed with lime, for external work such as pargeting or as an infill in timber-framed buildings. In such situations the surface had to be worked to a smooth finish and protected by effective roofing. Plaster of Paris is a pure form of gypsum plaster originally obtained in Paris. Martinís cement and Keeneís cement, both patented in the 1830s, involved the modification of gypsum plaster through heating and chemical treatments to produce a material which reliably set more slowly than gypsum but more rapidly than lime. This obviated the problems of difficulty in working and delay before decoration could be carried out.
Synonyms: plaster; plaster of Paris; gypsum cement; calcium sulphate hemihydrate
Trench (2000); Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated)
 
 

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