Glossary.
Materials used in 19th and 20th century Plaster Architecture.
By: JoAnn Cassar and Roberta de
Angelis
A. (alum- azurite)
Alum - A general name used
for aluminium sulphate salts. Most commonly the term alum, or potash alum,
refers to aluminium potassium sulphate. It is a colourless, crystalline
material. Other materials referred to as alum are aluminium sulphate or
the mixture of aluminium sulphates obtained by treating pulverised bauxite
with sulphuric acid, ferric ammonium sulphate, chromium sodium sulphate
and chromium ammonium sulphate. Alum is listed among the inorganic additives
used for stucco marble preparation according to literature. See also :
alum-gypsum.
Synonyms: aluminium potassium sulphate;
aluminium ammonium sulphate; aluminium sulphate; alum cake; alunite.
Wittenburg (1999); Museum
of Fine Arts, Boston (2000)
Alum-gypsum - It 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 1960s.
Wittenburg (1999); Leixner (1993)
Aluminous cement -
See cement.
RS Means Building Glossary (undated)
Ammonium carbonate - A white
powder that smells strongly of ammonia. Ammonium carbonate slowly decomposes
in air to form ammonia and carbon dioxide. It is used in ammonium casein
glue. Ammonium carbonate is commonly called hartshorn because it was historically
prepared by the destructive distillation of the antlers from harts (red
deer). Hartshorn is actually composed of a double salt of ammonium bicarbonate
and ammonium carbamate.
Synonyms: hartshorn; volatile alkali;
carbonate of ammonia; smelling salts; crystal ammonia; ammonium sesquicarbonate;
sal volatile; rock ammonia.
Museum of Fine Arts, Boston (2000)
Anhydrite CaSO4
- A naturally occurring mineral of anhydrous calcium sulphate that is often
found in gypsum deposits. Anhydrite was first identified as a mineral in
deposits at Innsbruck, Austria. Anhydrite can be transparent or translucent
and has a lustrous sheen. It occurs in several colours such as white, grey,
blue, pink, red and lavender. Anhydrite was used in ancient Egypt for carved
objects and vessels, many of which are in the shape of animals (Fay, 1998).
It is used in the manufacture of Portland cement to control the set.
Synonyms: blue marble; calcium sulphate.
Museum of Fine Arts, Boston (2000);
RS Means Building Glossary (undated)
Anhydrous lime -
See lime.
RS Means Building Glossary (undated)
Animal black - An impure black
carbon pigment prepared from burnt animal bones. Animal black, or bone
black, contains about 10% carbon along with 84% calcium phosphate with
smaller amounts of magnesium phosphate and calcium carbonate. The blue-black
pigment is denser than carbon black and has a good working quality for
oil paints and watercolours. A fine particle grade of bone black is now
sold as ivory black and an inferior grade has been sold under the name
of Paris black. Drop black is dried lumps formed after bone black is mixed
with water and glue. Drop black was commonly used in the 19th century
for house paints.
Synonyms: bone black; ivory black;
drop black; Frankfort black; German black; Pigment Black 9; CI 77267; Paris
black; abaiser.
Museum of Fine Arts, Boston (2000)
Animal glue - A strong, liquid
adhesive consisting primarily of gelatin and other protein residues of
collagen, keratin or elastin. The primary amino acids in animal glues are:
glycine (24.7%), proline (13%), analine (10.1%), glutamic acid (9.7%),
arginine (8.2%) and hydroxyproline (7.4%) (Mills and White 1994). Gelatin
(size) is similar to glue, but purer and better refined. Animal glue has
been made from ancient times from bones, skins and intestines of animals
(fish, goats, sheep, goats, cattle, horses, etc.). These agglutinating
materials are hydrolysed and broken down in boiling water; the cooled solution
yields a jelly-like substance which is gelatin or glue. The water soluble
glue occurs in a wide variety of forms and colours ranging from transparent
to opaque and white to brown. Glue is soaked in cool water to form a turbid
jelly that will become clear and thinner with gentle heating. Glue will
decompose and darken when it is boiled. Top-quality animal glues are made
from rabbitskin, sturgeon bladders and parchment clippings. Hide glues
are used in the manufacture of gessoes, gilding and paints. Animal
glues are available as, pellets, hot melts or a liquid solutions (with
a plasticizer or preservative).
Synonyms: glue; gelatin; size; isinglass;
fish glue; bone glue; parchment glue; Cologne glue; calfskin glue; nikawa;
hide glue; rabbitskin glue; sturgeon glue; pearl glue; carpenter's glue;
scotch glue.
Museum of Fine Arts, Boston (2000)
Antifreeze - An additive used
to lower the freezing point of a liquid. When added to fresh mortar or
rendering, the anti-freeze additive increases the rate of heat evolution
by accelerating the set. The additive is here often calcium chloride.
Ashurst (1983); Museum of Fine Arts,
Boston (2000)
Aqua regia - Common
name for an acid mixture that contains 3 parts hydrochloric acid and 1
part nitric acid. Aqua regia was used to produce tin chloride, also called
killed spirits, in the 18th century. This dark red colorant was made by
dropping a block of tin in the aqua regia solution. Aqua regia will dissolve
all metals except silver.
Synonyms: nitrohydric acid; yellow
fuming liquid; nitro-muriatic acid; nitrohydrochloric acid; chloronitrous
acid; chlorazotic acid.
Museum of Fine Arts, Boston (2000)
Architectural coating - A
paint or varnish designed for use on the interior and exterior of buildings.
Architectural coatings are used for protection and decoration on residential,
commercial, institutional and industrial buildings. Under normal weathering
and use, the lifetime of an architectural coating is expected to be 5-20
years.
Museum of Fine Arts, Boston (2000)
Argillaceous limestone - A
limestone that contains a significant amount of clay. Argillaceous limestone
is used in cement manufacturing.
Synonyms: pelitic; cement rock.
Museum of Fine Arts, Boston (2000)
Artificial marble -
A synthetic, moulded stone prepared to imitate the appearance of marble.
One type of artificial marble, called Marbelite, is made by heating potassium
alum in water then adding 10% heavy spar and marble dust (Brady 1971).
Another type of artificial marble, called Exsilite, is made by fusing grains
of silica and pigments to form a slab that simulates onyx marble. Artificial
marble is one historic technique for decorating architectural surfaces.
Other techniques besides artificial marble are scagliola, stucco marble,
stucco lustro and marmorino. See also : artificial stone
Synonyms: Marbelite; Exsilite.
Brady (1971); Wittenburg (1999);
Museum of Fine Arts, Boston (2000)
Artificial stone - Any mixture
of cement or plaster prepared to imitate the appearance of natural stone.
In early Egyptian tombs and Roman buildings, walls were coated with lime
and gypsum plaster then painted to simulate the appearance of natural stone
(Proudfoot 1996). By the 16th century, recipes for artificial stones included
marble dust, lime and glue. Manufacturing centres were preparing cast stones
based on terra cotta (Coade Stone) or cement (Pulham stone, Haddon stone)
by the mid 19th century for use in buildings, statuary and decoration.
Also in the 19th century, various mixtures of modified gypsum plasters,
such as Keeneís cement, crushed stone and colouring materials were patented
as artificial marbles, many of which were case into slabs for interior
decoration. Cement, mixed with sand and crushed stone, and often
referred to as cast, reconstituted or reconstructed stone, was widely used
from the late 19th century in Europe and North America to produce balustrades,
columns, architraves, arches and tracery windows. Various aggregates such
as granite and other stone dusts, slag and crushed brick were used to produce
a range of colours and textures; pigments could also be introduced. Artificial
stone can often be distinguished from natural stone by its appearance and
by the fact that the latter is colder to the touch. More precise identification
of the simulant can involve microscopic examination and chemical analysis
of its components.
Synonyms: cast stone; reconstructed
stone; reconstituted stone; oxychloride cement; renders; Victoria stone;
Protean stone; Frear stone; Siliceous Concrete Stone; Coade's stone; Rangerís
artificial stone; Permastone; Pulham stone; Haddon stone; Bradstone; Empire
Stone; Pulhamite Stone; Guattaris marble; artificial marble; scagliola;
marezzo; stucco lustro.
Trench (2000); Proudfoot (1996);
Museum of Fine Arts, Boston (2000); English Heritage (2000)
Asbestos - A common
name given to any of several fibrous silicate minerals. The most widely
used asbestos mineral is a type of serpentine called chrysotile (white
asbestos). Other asbestos minerals are: riebeckite, crocidolite (blue asbestos),
amianthus, anthophyllite, amphibole, amosite (brown asbestos), tremolite,
or actinolite. Asbestos is non-combustible and heat resistant. It was used
by the ancient Greeks, Egyptians and Chinese as a fireproof fabric. In
the 19th and early 20th centuries, asbestos was used for fireproofing
and insulating new houses. Small asbestos fibres were mixed with binders
and compressed into boards, shingles, tiles and sprayed onto ceilings.
Health concerns have limited the use of asbestos since the early 1960s.
In the U.S., it was declared a hazardous material in 1986.
Synonyms: amphibole; asbestus; serpentine;
earth flax; chrysotile; cork fossil; mountain leather; mountain cork; mountain
flax; mineral fibre; amosite; crocidolite; silicate fibre; amianthus; riebeckite;
anthophyllite; tremolite; actinolite; salamander wool.
Museum of Fine Arts, Boston (2000)
Ash (residue) - A greyish
white to black powdery residue that remains after a substance has burned.
The residual ash is composed of non-combustible, or mineral, matter such
as silica, alumina, iron oxide, clay, etc. Ash from plant material generally
contains high amounts of lime, sodium carbonate and/or potassium carbonate.
Wood ash was the principal source for potassium for several hundred years.
Phosphorus was obtained from the ash of animal bones (calcium phosphate).
Ash from sea plants contains high amounts of iodine.
Museum of Fine Arts, Boston (2000)
Azurite 2CuCO3-Cu(OH)2
- A deep blue mineral composed of basic copper carbonate that is naturally
found with the green copper carbonate mineral called malachite. Azurite
and malachite have been used as gemstones and paint pigments since before
3000 BCE. They are prepared as pigments by careful selection, grinding,
washing and levigation. Coarsely ground azurite gives a deep blue colour
while finely ground particles give a lighter more transparent tone. Azurite
is lightfast but is sensitive to acids and sulphur fumes. Basic copper
carbonate can also be made artificially by colouring chalk with copper
sulphate. The synthetic pigment, called blue verditer, blue bice, Bremen
blue or ashes blue, tends to have regularly sized particles with rounded
edges. The colour is similar to finely ground azurite. It is listed among
the pigments used for colouring stucco marble in the nineteenth and twentieth
century.
Synonyms: blue verditer; mountain
blue; Pigment Blue 30; CI 77420; ashes blue; Bremen blue; blue bice; Armenian
stone; lapis armenius; chessylite; blue malachite; mineral blue; basic
copper carbonate; basic cupric carbonate; copper blue; chessy copper; bleu
d'Allemagne (Fr.); Bergblau (Ger.); Bergasur; Azurit (Ger.); azurite (Fr.);
azzurrite (It.); azzurro della magna (It.); azurita (Sp.); azurium
citramarinum.
Wittenburg (1999); Museum
of Fine Arts, Boston (2000)
Bibliography
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