Glossary.
Materials used in 19th and 20th century Plaster Architecture.
By: JoAnn Cassar and Roberta de
Angelis
A. (abrasive-alizarin)
Abrasive - Hard, fine
particles used to polish metals, stone, wood, glass and other materials.
Naturally occurring materials used as abrasives include diamond, emery,
corundum, sand, crushed garnet, quartz, pumice, diatomite, kaolin, fuller's
earth, talc, chalk and cuttlefish bone. Manufactured materials used as
abrasives include silicon carbide, aluminium oxide, zirconium oxide, titanium
dioxide, green rouge (chromic oxide), tin oxide, cerium oxide, glass, boron
carbide, boron nitride and diamond. Abrasives are sold as powders, slurries
and as abrasive clothes, papers and wheels. They are characterised by hardness
and particle size. Their hardness can be measured on the Mohs scale in
which the diamond is rated as a 10. Mild abrasives, such as chalk and talc,
have a hardness of 1-2 Mohs. Diamond and silicon carbide are hard abrasives.
Particle size depends on the mesh of the sieves used for separation, i.e.
a 600 grit abrasive contains particles 8 micrometers and smaller.
Synonyms: diamond; emery; corundum;
sand; garnet; quartz; pumice; diatomite; kaolin; fuller's earth; talc;
chalk; cuttlefish bone; silicon carbide; aluminium oxide; zirconium oxide;
titanium dioxide; green rouge; chromic oxide; tin oxide; cerium oxide;
glass; boron carbide; boron nitride; steel wool; abrasive paper; lubrisil,
micromesh; abrasive powder; crocus powder; jewellers rouge; rottenstone;
tripoli powder; whiting.
Museum of Fine Arts, Boston (2000)
AC - asbestos cement.
RS Means Building Glossary (undated)
Acceleration - (1) An
increase in velocity or rate of change. (2) The ordered or voluntarily
expedited performance of construction work at a faster rate than anticipated
in the original schedule, the purpose of which is to recapture project
delay. This is accomplished by increasing labor hours and other resources.
(3) The speeding up of the setting or hardening process of concrete by
using an additive in the mix. The process of acceleration allows forms
to be stripped sooner or floors finished earlier.
RS Means Building Glossary (undated)
Accelerator - A compound that
speeds up a chemical reaction. When added to paint, concrete, mortar, or
grout mix, it speeds the rate of hydration and thereby causes it to set
or harden sooner. For example, alum is used to decrease the setting time
of plaster of Paris or Portland cement and metallic soaps are used to hasten
the drying time for oil paints.
Synonyms: promoter; activator; accelerant;
drier.
Museum of Fine Arts, Boston (2000);
RS Means Building Glossary (undated)
Acoustical plaster -
A sound-absorbent plaster. Acoustical plasters, developed in the 1920s,
were made porous and sound-absorbing by the incorporation of fibrous or
porous aggregates, such as wood, mineral wool, cork or asbestos. An alternative
method called Hushkote, incorporated yeast in the plaster mixture to generate
bubbles that would increase the porosity. By 1945, spray-applied acoustical
coatings were available (Spray-Acoustic). These generally incorporated
mineral wool or asbestos in a fireproof binder.
Synonyms: Sabinite plaster; Akoustilith
plaster; Macoustic; Kilnoise; Kalite; Hushkote.
Museum of Fine Arts, Boston (2000)
Acrylic resin - Colourless,
thermoplastic polymer or copolymer of acrylic acid, methacrylic acid or
acrylonitrile. Acrylic resins are a commercially important family of polymers
that were first discovered in 1880 by the Swiss chemist Georg W.A. Kahlbaum.
Otto Röhm of Germany thoroughly described their production in his
doctoral thesis (1901) then later patented the process in 1915. Polymethyl
methacrylate was first marketed by Rohm and Haas in Germany in 1927. Acrylics
have been sold as glass substitutes and as adhesives, varnishes and
paint media. Acrylic resins range from soft, tacky materials to hard solids.
They are glossy, crystal clear with good shock and water resistance. They
are stable to outdoor weathering and resistant to chemicals including by
mild acids and bases. Acrylics are used as paints, coatings and adhesives.
Synonyms : acrylics; acrylate; methacrylate;
Plexigum® [Rohm & Haas]; Lucite® [DuPont]; Paraloid® [Rohm
& Haas]; Elvacite® [DuPont]; Plexiglas® [Rohm & Haas];
Perspex®; Magna [Bocour]; Liquitex [Permanent Pigments]; Shiva [Shiva];
Hyplar [Grumbacher]; Aqua-tec [Bocour].
Museum of Fine Arts, Boston (2000)
Additive - A substance
that is added to a material to enhance or modify its characteristics, such
as curing time, plasticity, colour, or volatility. Additives were used
for the preparation of stucco marble. The aim of inorganic additives is
to increase hardness, resistance, and durability and to retard setting.
They are added at some stage of the working process. The aim of adding
organic substances is either to improve the workability, to harden the
mass, to retard setting, or to influence the mechanical properties of the
stucco mass in a way that it can be polished so that a sufficient gloss
is obtained.
Wittenburg (1999); RS Means Building
Glossary (undated)
Adhesive - A substance that
adheres one surface to another. Those which have been used for several
millennia are also known as glues, the weaker, more refined ones often
being called size. Adhesives may be classified as inorganic and organic
adhesives. Examples of inorganic adhesives are water glass, plaster of
Paris and Portland cement. Organic adhesives may be subdivided by origins
into animal (hide, bone, blood, casein, etc.), vegetable (starch, gum,
resin, etc.) and synthetic (acrylic, vinyl acetate, cyanoacrylate, epoxy
, silicone, etc.). Adhesives provide a wide selection of properties, solubility,
tackiness, bonding time and bonding strength. They can be used on nearly
every kind of surface. In some cases, surface treatment, abrasion or an
adhesion promoter may be needed to increase the strength or durability
of the adhesive bond.
Synonyms: mastic; cement; glue;
size; mucilage; paste.
Trench (2000); Museum of Fine Arts,
Boston (2000)
Admixture - An ingredient
other than cement, aggregate, or water that is added to a concrete or mortar
mix to affect the physical or chemical characteristics of the concrete
or mortar. The most common admixtures affect plasticity, air entrainment,
and curing time.
RS Means Building Glossary (undated)
Air-entraining agent - An
additive to hydraulic cement or an admixture for concrete or mortar that
causes air to be incorporated in the form of minute bubbles on the concrete
or mortar during mixing, usually to increase its workability and frost
resistance. Air-entrained Ordinary Portland Cement contained agents, such
as calcium lignosulphate, which entrain 4%-5% minute, discontinuous uniformly
distributed air bubbles, The density reduction may mean a decrease in strength
of up to 15%.
Ashurst (1983); RS Means Building
Glossary (undated)
Air-entraining hydraulic cement
- Hydraulic cement containing an air-entraining addition in such
amount to cause the product to entrain air in mortar within specified limits.
RS Means Building Glossary (undated)
Albarium - A white lime used
for stucco.
RS Means Building Glossary (undated)
Alabaster - A fine-grained
marble-like mineral of gypsum (hydrated calcium sulphate). Alabaster is
usually a translucent white or pink but may also be a muted red, yellow
or grey. It is soft and can be scratched slightly with a fingernail. It
also dissolves slowly in wet environments. Alabaster was used since ancient
times in the Near East, Egypt, Greece and Italy for ornamental building
work, sculpture, vases and small decorative carvings. Powdered alabaster
has been used as a paint pigment called mineral white or terra alba. The
word alabaster is derived from the Greek word for substance. In ancient
times, it was used to refer to several other minerals such as limestone
onyx, travertine and calcite.
Synonyms: gypsum; satin spar; alabastrine.
Museum of Fine Arts, Boston (2000)
Alabaster-gypsum - It
is mentioned as the basic material of scagliola according to various written
sources.
Wittenburg (1999)
Albumen - The protein mixture
found in egg whites. It has and is used as an adhesive, coating, and binder.
See also egg white. Synonyms: egg white; albumin.
Museum of Fine Arts, Boston (2000)
Albumin - A naturally occurring,
water-soluble protein found in egg white, milk and blood. When spelled
as albumen, the use generally refers only to egg white protein. Albumin
is a strong, coagulating protein that is used in adhesives and varnishes.
Dried albumin powder is yellowish and forms a colourless solution in water.
Albumin proteins will remain water soluble used unless heated to temperatures
above 50*C (122*F) or exposed to intense or long-term light. Albumin is
listed among the organic additives used for the preparation of stucco marble
according to literature. According to Cröcker, egg-albumin was especially
used for white marble imitations on sculptures. See also albumen, egg white,
and casein.
Synonyms: albumen; egg white
Wittenburg (1999); Cröcker
(1736, reprinted 1982); Museum of Fine Arts, Boston (2000)
Alite - The primary
constituent of Portland cement clinker. Alite is composed of tricalcium
silicate and small amounts of magnesium oxide, aluminum oxide, ferric oxide,
and other materials.
RS Means Building Glossary (undated)
Alizarin, natural - Natural
alizarin is a red colorant extracted along with purpurin from the roots
of the madder plant, Rubia tinctoria. The chemical name for alizarin is
1,2-dihydroxyanthraquinone. It has been used as a dye and pigment since
ancient times. The colorant was first isolated in 1862 by Colin and Robiquet
in France. The synthetic form of alizarin was first made in 1868 by Carl
Graebe and Carl Lieberman, from anthracene.
Synonyms: madder; alizarine; 1,2-dihydroxyanthraquinone;
Natural Red 6, 8-12; CI 75330.
Museum of Fine Arts, Boston (2000)
Bibliography
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