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| A Pallete |
Oil painting is the
process of painting with pigments that are bound with a medium of
drying oil. Commonly used drying oils include linseed oil, poppyseed
oil, walnut oil, and safflower oil. The oil may be boiled with a resin,
such as pine resin or frankincense to create a varnish; often prized for
its body and gloss. Different oils confer various properties to the oil
paint, such as less yellowing or different drying times. Certain
differences are also visible in the sheen of the paints depending on the
oil. An artist might use several different oils in the same painting
depending on specific pigments and effects desired. The paints
themselves also develop a particular consistency depending on the
medium.
Although
oil paint was first used for the Buddhist Paintings by Indian and
Chinese painters in western Afghanistan sometime between the fifth and
tenth centuries, it did not gain popularity until the 15th century. Its
practice may have migrated westward during the Middle Ages. Oil paint
eventually became the principal medium used for creating artworks as its
advantages became widely known. The transition began with Early
Netherlandish painting in northern Europe, and by the height of the
Renaissance oil painting techniques had almost completely replaced
tempera paints in the majority of Europe.
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| Tubes of Paint |
In recent years,
water miscible oil paint has come to prominence, to some extent
replacing the usage of traditional oils. Water soluble paints contain an
emulsifier which allows them to be thinned with water (rather than with
paint thinner), and allows very fast drying times (1–3 days) when
compared with traditional oils (1–3 weeks).
Techniques
Traditional
oil painting techniques often begin with the artist sketching the
subject onto the canvas with charcoal or thinned paint. Oil paint is
usually mixed with linseed oil, artist grade mineral spirits or other
solvents to create a thinner, faster or slower drying paint. Because
these solvents thin the oil in the paint, they can also be used to clean
paint brushes. A basic rule of oil paint application is 'fat over
lean'. This means that each additional layer of paint should contain
more oil than the layer below to allow proper drying. If each additional
layer contains less oil, the final painting will crack and peel. There
are many other media that can be used in oil painting, including cold
wax, resins, and varnishes. These additional media can aid the painter
in adjusting the translucency of the paint, the sheen of the paint, the
density or 'body' of the paint, and the ability of the paint to hold or
conceal the brushstroke. These variables are closely related to the
expressive capacity of oil paint.
Traditionally,
paint was transferred to the painting surface using paint brushes, but
there are other methods, including using palette knives and rags. Oil
paint remains wet longer than many other types of artists' materials,
enabling the artist to change the color, texture or form of the figure.
At times, the painter might even remove an entire layer of paint and
begin anew. This can be done with a rag and some turpentine for a
certain time while the paint is wet, but after a while, the hardened
layer must be scraped. Oil paint dries by oxidation, not evaporation,
and is usually dry to the touch within a span of two weeks. It is
generally dry enough to be varnished in six months to a year. Art
conservators do not consider an oil painting completely dry until it is
60 to 80 years old.
History
Although
the history of tempera and related media in Europe indicates that oil
painting was discovered there independently, there is evidence that oil
painting was used earlier in Afghanistan. Surfaces like shields — both
those used in tournaments and those hung as decorations — were more
durable when painted in oil-based media than when painted in the
traditional tempera paints.
Most
Renaissance sources, in particular Vasari, credited northern European
painters of the 15th century, and Jan van Eyck in particular, with the
"invention" of painting with oil media on wood panel. However,
Theophilus (Roger of Helmarshausen?) clearly gives instructions for
oil-based painting in his treatise, On Various Arts, written in 1125. At
this period it was probably used for painting sculptures, carvings and
wood fittings, perhaps especially for outdoor use. Early Netherlandish
painting in the 15th century was, however, the first to make oil the
usual painting medium, and explore the use of layers and glazes,
followed by the rest of Northern Europe, and only then Italy. Early
works were still panel paintings on wood, but around the end of the 15th
century canvas became more popular, as it was cheaper, easier to
transport, and allowed larger works. Venice, where sail-canvas was
easily available, led the move. The popularity of oil spread through
Italy from the North, starting in Venice in the late 15th century. By
1540 the previous method for painting on panel, tempera, had become all
but extinct, although Italians continued to use fresco for wall
paintings, which was more difficult in Northern climates.
Ingredients
The
linseed oil itself comes from the flax seed, a common fiber crop. It is
interesting to note that linen, an important "support" for oil painting
(see below) also comes from the flax plant. Safflower oil, or the more
traditional walnut or poppyseed oil, are sometimes used in formulating
lighter colors such as white because it "yellows" less on drying than
does linseed oil, but it has the slight drawback of drying more slowly.
Recent
advances in chemistry have produced modern water miscible oil paints
that can be used with and cleaned up with water. Small alterations in
the molecular structure of the oil creates this water miscible property.
A
still-newer type of paint, heat-set oils, remain liquid until heated to
265–280 °F (130–138 °C) for about 15 minutes. Since the paint never
dries otherwise, cleanup is not needed (except when one wants to use a
different color and the same brush). Although not technically true oils
(the medium is an unidentified "non-drying synthetic oily liquid,
imbedded with a heat sensitive curing agent"), the paintings resemble
oil paintings and are usually shown as oil paintings.
Supports for oil painting
Traditional
artists' canvas is made from linen, but less expensive cotton fabric
has gained popularity. The artist first prepares a wooden frame called a
"stretcher" or "strainer". The difference between the first and second
is that stretchers are slightly adjustable, while strainers are rigid
and lack adjustable corner notches. The canvas is then pulled across the
wooden frame and tacked or stapled tightly to the back edge. Then, the
artist applies a "size" to isolate the canvas from the acidic qualities
of the paint. Traditionally, the canvas was coated with a layer of
animal glue (size), (modern painters will use rabbit skin glue) and
primed with lead white paint, sometimes with added chalk. Panels were
prepared with a gesso, a mixture of glue and chalk.
Modern
acrylic "gesso" is made of titanium dioxide with an acrylic binder. It
is frequently used on canvas, whereas real gesso is not suitable for
that application. The artist might apply several layers of gesso,
sanding each smooth after it has dried. Acrylic gesso is very difficult
to sand. One manufacturer makes a sandable acrylic gesso, but it is
intended for panels only, not canvas. It is possible to tone the gesso
to a particular color, but most store-bought gesso is white. The gesso
layer will tend to draw the oil paint into the porous surface, depending
on the thickness of the gesso layer. Excessive or uneven gesso layers
are sometimes visible in the surface of finished paintings as a change
in the layer that's not from the paint.
Standard
sizes for oil paintings were set in France in the 19th century. The
standards were used by most artists, not only the French, as it was –
and evidently still is – supported by the main suppliers of artist
materials. The main separation from size 0 (toile de 0) to size 120
(toile de 120) is divided in separate runs for figures (figure),
landscapes (paysage) and marines (marine) which more or less keep the
diagonal. Thus a 0 figure corresponds in height with a paysage 1 and a
marine 2.
Although
surfaces like linoleum, wooden panel, paper, slate, pressed wood, and
cardboard have been used, the most popular surface since the 16th
century has been canvas, although many artists used panel through the
17th century and beyond. Panel is more expensive, heavier, harder to
transport, and prone to warp or split in poor conditions. For fine
detail, however, the absolute solidity of a wooden panel gives an
advantage.
Process
The
artist might sketch an outline of their subject prior to applying
pigment to the surface. "Pigment" may be any number of natural
substances with color, such as sulphur for yellow or cobalt for blue.
The pigment is mixed with oil, usually linseed oil but other oils may be
used as well. The various oils dry differently, creating assorted
effects.
Traditionally,
artists mixed their own paints from raw pigments that they often ground
themselves and medium. This made portability difficult and kept most
painting activities confined to the studio. This changed in the late
1800s, when oil paint in tubes became widely available. Artists could
mix colors quickly and easily, which enabled, for the first time,
relatively convenient plein air (outdoor) painting (a common approach in
French Impressionism).
The
artist most often uses a brush to apply the paint. Brushes are made
from a variety of fibers to create different effects. For example,
brushes made with hog's bristle might be used for bolder strokes and
impasto textures. Fitch hair and mongoose hair brushes are fine and
smooth, and thus answer well for portraits and detail work. Even more
expensive are red sable brushes (weasel hair). The finest quality
brushes are called kolinsky sable; these brush fibers are taken from the
tail of the Siberian mink. This hair keeps a superfine point, has
smooth handling, and good memory (it returns to its original point when
lifted off the canvas); this is known to artists as a brush's "snap."
In
the past few decades, many synthetic brushes have come on the market.
These are very durable and can be quite good, as well as cost efficient.
Floppy fibers with no snap, such as squirrel hair, are generally not
used by oil painters. Sizes of brushes also are widely varied and used
for different effects. For example, a "round" is a pointed brush used
for detail work. "Flat" brushes are used to apply broad swaths of color.
"Bright" is a flat with shorter brush hairs. "Filbert" is a flat with
rounded corners. "Egbert" is a very long "Filbert" and is rare. The
artist might also apply paint with a palette knife, which is a flat,
metal blade. A palette knife may also be used to remove paint from the
canvas when necessary. A variety of unconventional tools, such as rags,
sponges, and cotton swabs, may be used. Some artists even paint with
their fingers.
Most
artists paint in layers, which is simply called "Indirect Painting".
The method was first perfected through an adaptation of the egg tempera
painting technique and was applied by the Flemish painters in Northern
Europe with pigments ground in linseed oil. More recently, this approach
has been called the "Mixed Technique" or "Mixed Method". The first coat
(also called "underpainting") is laid down, often painted with egg
tempera or turpentine-thinned paint. This layer helps to "tone" the
canvas and to cover the white of the gesso. Many artists use this layer
to sketch out the composition. This first layer can be adjusted before
moving forward, an advantage over the 'cartooning' method used in Fresco
technique. After this layer dries, the artist might then proceed by
painting a "mosaic" of color swatches, working from darkest to lightest.
The borders of the colors are blended together when the "mosaic" is
completed. This mosaic layer is then left to dry before applying
details.
Artists
in later periods, such as the impressionist era, often used this
Wet-on-wet method more widely, blending the wet paint on the canvas
without following the Renaissance-era approach of layering and glazing.
This method is also called "alla prima". This method was created due to
the advent of painting outdoors, instead of inside a studio. While
outside, an artist did not have the time to let each layer of paint dry
before adding a new layer. Several contemporary artists use a blend of
both techniques, which can add bold color (wet-on-wet) as well as the
depth of layers through glazing.
When
the image is finished and has dried for up to a year, an artist often
seals the work with a layer of varnish that is typically made from damar
gum crystals dissolved in turpentine. Such varnishes can be removed
without disturbing the oil painting itself, to enable cleaning and
conservation. Some contemporary artists decide not to varnish their
work, preferring that the surfaces remain varnish-free.