Glossary of Common Terms
abrasion: Material loss caused by excess
friction. Examples include paint loss caused during improper varnish removal or a varnish loss caused by friction.
acrylic: A family of synthetic resins made
by polymerizing esters of acrylic acids.
alkyd: A synthetic resin which is the
condensation product of a polybasic acid such as phthalic, a polyhydric alcohol
such as glycerin and an oil fatty acid.
alla
prima: An Italian
phrase meaning painted solely wet in wet and usually, but not necessarily, at a
single sitting. It is used most commonly with reference to oil painting.
binder: The nonvolatile portion of a
coating vehicle which is the film-forming ingredient used to bind the pigment
particles together.
blanching: A term applied to lacquer when
they become partially opaque, cloudy or transparent upon application or
drying. Fast-evaporating solvents may cool the film enough to cause water
condensation, precipitating solid materials.
blending: Blending is most commonly used
with reference to academic painting to mean the blending together of separate
touches of color for half tones until the graduations of tone and the marks of
the brush are imperceptible.
blocking-in: Usually refers to the broad
application of masses of light, shade, and color, in the early stages of a
painting. It helped to obliterated rapidly the glaring bright of the
ground.
bloom: A bluish fluorescent coat which
forms on the surface of some films.
body: Common term for the degree of
viscosity of a paint or varnish, as "a lot of body" or "not much
body." A practical term used to give a qualitative picture of
consistency.
chalking: The presence of a loose powder on
the surface of a paint after exposure to the elements.
chiaroscuro: The use of graduation of light
and dark to describe forms in drawing and painting.
color: A generic term referring
exclusively to all colors of the spectrum, including white and black.
Color is described by three properties: hue, lightness and saturation.
(1) Hue (color, character, dominant wavelength): blue, green, red, etc.
(2) Lightness (brightness, reflectance, value): position on the gray scale
between pure black and pure white (3) Saturation (purity, grayness,
cleanliness, muddiness, chroma): purity or intensity of color.
craquelure: A pattern of cracks that develops
on the surface of a painting as a result of the natural drying and aging of the
paint film.
crawling: The tendency of a liquid to draw
up and bead on the surface.
crazing: Fine lines or minute surface
cracks occurring on painted surfaces due to unequal contraction in drying or
cooling.
crocking: Removal of color on abrasion or
rubbing.
direct painting: Using paint in an opaque manner in a single application.
drier: Any catalytic material which when
added to a drying oil accelerates drying or hardening of the film.
drying
oils: Oils which
have the property of forming a solid, elastic surface when exposed to air in
thin layers. The drying oils most commonly used in oil painting were
linseed oil, walnut oil and poppy oil. Examples of non-drying oil
unsuitable for painting are olive oil and almond oil.
efflorescence: A phenomena whereby a whitish
crust of fine crystals forms on a painted surface. These are usually
sodium salts which diffuse through the paint film from the substrate.
egg
tempera painting: Egg (either whole, yolk or white) can be used as a pigment binder.
Tempera painting was very popular until the late fifteenth century.
emulsion: A suspension of fine particles or
globules of a liquid within a liquid.
enamel
paints: Historically, enamel has described decorative and protective glassy coatings on
metal as well as glassy, decorative coatings on glass. Enamel has also
implied certain organic coating such as paints or lacquers.
extender: A pigment which contributes very
little hiding to the system, but does reinforce the film and alter the gloss.
fly
specks: The bodily
waste discharged by flies. Fresh specks can be cleaned off with
moistened cotton swabs; however, aged specks can not be cleaned off but are sometimes removed mechanically.
fugitive
pigment: A phrase
used to describe a pigment's impermanence and tendency to fade or change color
under the influence of natural effects such as sunlight.
gesso: Traditionally a lean layer of
size and chalk to form a ground on which to paint.
glair: Egg white. It is used in
egg tempera painting and as a coating material.
glaze: 1) To cover paler under painting
with a layer consisting of transparent pigments and excess medium.
Traditionally used to add color to forms modeled in monochrome opaque
paint. 2) To impart a glass-like surface. Aged glaze is very
sensitive to solvents.
gloss: The shine, sheen or luster of the
surface of a coating. Specular gloss: the ratio of reflected to incident
light at specified angles of incidence. Most common are angles of 20, 60
and 85 degrees. See also sheen.
grime: Surface dirt: a combination of
air-borne soot, nicotine, and cooking grease. Dirt can be in the varnish,
on top of the paint layer, or on top of the varnish.
ground: A layer of opaque paint applied
to a support to provide a suitable color and texture on which to draw or paint.
haze: The dullness of a surface
removable by polishing. It usually results from faulty solvent balance or
incompatibility of ingredients.
impasto: The texture created in a paint
surface by the movement of the brush. Impasto usually implies thick,
heavy brushwork, but the term also refers to the crisp, delicate textures found
in smoother paint surfaces.
inpainting: Paint applied over losses
only. This is a technique commonly used by conservators to unify a
painting that has suffered paint loss.
lacquer: A term which usually indicates
that the material dries by evaporation and forms a film from the nonvolatile
constituents.
lake: A colored natural or synthetic
dye absorbed onto a semi-transparent base and used as a pigment.
latex: a generic term describing stable
dispersions of resin particles in a water system.
leaching: When solvents are applied to a
paint film, solvent soluble compounds are removed and the film becomes more
brittle.
lean
paint: Lean oil
color is paint in which the oil or fat content has been reduced, usually by
indirect means such as diluting the paint with turpentine.
light
fastness:(1)
ability to withstand color changes on exposure to light (2) the relative degree
of change or lack of change in color of materials exposed to the same amount
and character of light.
lightness: (Brightness, reflectance, value)
Position on the grey scale between pure black and pure white.
linseed
oil: The most
popular drying oil used as paint medium. The medium hardens over several
weeks as components of the oil polymerize to form an insoluble matrix.
Driers can be added to accelerate this process.
loaded: A painting is said to be loaded
when it is painted thickly, often with a heavy impasto. A loaded brush is
one charged to its full capacity with paint.
luster: The gloss of a finish.
medium: The component of paint in which
the pigment is dispersed.
mildew: Organic surfaces exposed to high
temperature-humidity atmospheres are attacked by fungus growth. This dark
discoloration, usually a mold type of fungus but more commonly called
"mildew."
mineral
spirits: A
petroleum fraction with boiling range between 300 to 400ºF.
mottling: A film defect associated with
spraying. Appears as circular imperfections.
natural
varnish: Tree
resins (mastic and dammar), fossil resins (copal and amber), and insect resin
secretions (shellac).
oil: A general term from a
water-insoluble viscous liquid
oleoresinous: Indicating a material which has
been made by the combination of an oil and a resin.
opacity: Hiding power or the degree of
obliteration.
opaque: Impervious to light or not
translucent.
orange
peel: A pebbled
film surface similar to the skin of an orange in appearance. It is caused
by too rapid drying before leveling takes place.
over
paint: This paint
was not applied by the artist but applied at a later date. It not only
covers the original paint, but its presence often indicates an excessive
alteration of the image. Over painting is not an acceptable conservation
technique
paint
layer: The paint
layer is the actual layer or layers of color more-or-less opaque applied by the
artist in the execution of the painting.
pentimento: Derived from the Italian meaning
"repentance." Pentimenti are the changes in composition which a
painter makes while producing a painting. These alterations are often
visible in the infra-red, to x-rays and sometimes to the naked eye.
pigment: A finely divided, insoluble
substance which imparts color to the material to which it is added.
polar
solvents: Solvents
such as alcohols, ketones, etc., which contain oxygen, etc. These have
high dielectric constants.
polymer: A large molecule formed when many
molecules are linked together by polymerization.
priming: The application of sizes and/or
grounds to a support to prepare the painting's surface, modify its absorbency,
texture and color.
resin: An organic polymer in the form of
a crystalline or amorphous solid, or viscous liquid, of wither natural or
synthetic origins.
retouching: The work done by a restorer to
replace areas of loss or damage in a painting.
sagging: The tendency of a wet paint film
to flow downward and become thicker on vertical surfaces.
saturation: Purity or intensity of
color. Degree of freedom from grayness.
scumble: Very thin layer of opaque or
semi-opaque paint that partially hides the underlayer.
shade: The difference in appearance between
colors of similar hue.
sheen: A specular reflectance taken at a
low angle, usually 85 degrees.
sinking: The absorption of paint medium by
a lean underlayer to produce a matte or dead surface.
size: An adhesive diluted in
water. Usually means and animal glue consisting of collagen and gelatin,
rabbit skin glue, parchment glue, and edible jelly are all forms of gelatin.
stretcher: A rigid wooden frame over which a
canvas is usually stretched. The stretcher can be expanded by tapping
keys (wedges) inserted at the corners.
strainer: A stretcher from with fixed
corners. It cannot be expanded.
synthetic
resin: Complex,
substantially amorphous organic semi-solid or solid materials built up by
chemical reaction of simple molecules.
synthetic
varnishes:Polyvinyl
acrylate.
tacking
edges:The outside edges of a stretched canvas through which tacks are inserted attaching it onto the stretcher.
tempra: Usually refers to egg (either
whole, yolk, or white) used as the medium but can also refer to glue size.
thermoplastic: The term applied to resins which
soften and flow when heated.
thermosetting: The term applied to resins which
become hard after heating and cannot be resoftened.
toughness: The ability of a material to take
bending, impact, etc., without cracking.
turpentine
(spirits):The
traditional solvent or thinner for a drying oil (such as linseed oil) distilled
from the resin that is exuded by certain trees, e.g., the European larch, white
fir, and American longleaf pine.
ultraviolet: The light rays which are outside
of the visible spectrum at its violet end.
varnish: An applied surface film, usually
of a transparent, cloudless resin. It imparts an even gloss to the
surface, wetting the paint, and providing protection for it.
water
sensitive binder: Glue, gum arabic, starch, cellulose esters. These materials were used by
artists in the past and present in the construction of oil paintings.
white spirit: Turpentine substitute consisting
of naphtha thinners (solvent distilled from petroleum). They are
colorless hydrocarbons, boiling range 100 to 160ºC, used as a paint thinner.
Source: Smithsonian Museum Conservation Institute website http://www.si.edu/MCI/english/learn_more/taking_care/painting_glossary.html