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Binder - that which binds the pigment together in a paste and then adheres it to the surface of the painting. In oil paintings, it is usually linseed or poppy oil, in watercolour it is gum arabic, etc.
Conservation - keeping a painting in a condition of high quality so that it both looks as it should, and will resist physical change and damage. This prevents the need for restoration.
Egg tempera - the medium used before oils became popular during the Renaissance. The yolk of an egg is mixed with the ground pigment and applied with a soft brush usually with sharp, short strokes, and which dried very rapidly. Oil painting allowed for greater freedom, was easily blended, stayed wet for hours and days, and so eclipsed the use of egg tempera in the 15th century.
Glaze - A translucent layer of paint through which other layers of paint can be seen. This usually increases the sense of depth and luminosity of a painting, but if a painting is dirty or has an old varnish over it, then the effect of the glaze is neutralized.
Light-fast - the permanency of a pigment. Some pigments will stay virtually the same over decades and even centuries if proper care is taken, other are fugitive and will fade or darken over a short period of time when exposed to light. No painting should be exposed to direct sunlight. The proper varnish and the proper care can affect a pigment's permanence.
Linen - The material traditionally used as canvases for
oil paintings.
Linseed - a type of oil most commonly used in painting. In excessive quantities, it can yellow somewhat, which has led some artists to use poppy oil.
Medium - the type of binder used in painting, e.g. oils, acrylics, watercolor, etc.
Panel - a rigid support for painting, usually wood. This was used for egg tempera, because it is not as flexible as oil and has the tendency to crack when painted on linen. As oil became the medium of choice during 15th century, panels became less and less popular, as large (and small) canvases were lighter and easier to construct. However, some later artists preferred less flexible surfaces for oil paintings, and panels have remained in use.
Pigment - the mineral or organic source for paint, which is finely ground and mixed with a binder. Minerals that have traditionally been used are metals, types of earth, and even semi-precious stones in the case of lapis lazuli (ultramarine blue). Organic substances have included plant roots, and although they have been fairly widely used, they are not considered as light-fast as the most commonly used minerals. However, modern chemistry has come up with some organic pigments that have very high light-fast ratings.
Poppy - after linseed oil, the most commonly used oil in painting. It is considered not to yellow as much as linseed oil, but also is not quite as strong and permanent a binder.
Primer - a layer of paint put on a canvas after it has been
sized. Traditionally, this has been a lead based paint, but other
materials have come into use over the last few decades. The lack
of a primer, or a poor quality one, can cause paint to crack or peel
off the surface of the canvas.
Re-lining - the thin layer of oil is removed from its support and put onto a new, fresh canvas. This is usually done to prevent further deterioration if the old support is defective, or if the paint is peeling away from the surface. It is a delicate operation that must be done with much care and precision.
Restoration - repairing of damage done to a canvas to make it look as close to its original state as possible. This may include removal of dirt, filling in large cracks, re-lining, and delicately over-painting scratches. Proper conservation and care may prevent such eventualities.
Stretcher - the wood frame behind the painting over which
the canvas is stretched.
Size - usually rabbit skin glue, which comes in crystal form, is soaked in water, then gently heated and applied to the linen. This prevents the acids in the oil paint attacking the material, which would rot the canvas and cause it to become very brittle.
Varnish - a transparent, protective coating applied to the
canvas after the oil is completely dry. It can prevent scratches
from accidental blows, and is fairly easily removed if there is
a long term accumulation of dirt. Otherwise, the dirt becomes embedded
into the paint surface, and cleaning becomes a painstaking task.
However, varnishes, especially when old, can become yellow, and
need removal if the painting is to be seen properly.
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