Process of oil painting

Splined canvas, stapled stretched canvas and canvas boards


The Frankfurt Paradiesgärtlein, a German panel painting from circa 1410




A palette


The Cliffs at Etretat, Claude Monet, 1885

Process of oil painting

The process of oil painting varies from artist to artist, but often includes certain steps. First, the artist prepares the surface. 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. Before that it was panel, which is more expensive, heavier, less easy 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.

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, an artist mixed his or her own paints for each project. Handling and mixing the raw pigments and mediums was prohibitive to transportation. This changed in the late 1800’s, when oil paint in tubes became widely available. Artists could mix colors quickly and easily without having to grind their own pigments. Also, the portability of tube paints allowed for plein air, or outdoor painting (common to 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. Brushes made from miniver, which is squirrel fur, might be used for finer details. Sizes of brushes also create different effects. For example, a "round" is a pointed brush used for detail work. "Bright" brushes are used to apply broad swaths of color. 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, a method first perfected in the Egg tempera painting technique, and adapted in Northern Europe for use with linseed oil paints. The first coat or "underpainting" is laid down first, painted normally with turpentine thinned paint. This layer helps to "tone" the canvas, and cover the white of the gesso. Many artists use this layer to sketch out the composition. This layer can be adjusted before moving forward, which is an advantage over the 'cartooning' method used in Fresco technique. After this layer dries, one way the artist might then proceed is 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 layer is then left to dry before applying details. The artist may apply several layers of details, using a technique called 'fat over lean.' This means that each additional layer of paint is a bit oilier than the layer below, to allow proper drying. As a painting gets additional layers, the paint must get oilier (leaner to fatter) or the final painting will crack and peel. After it is dry, the artist will apply "glaze" to the painting, which is a thin, transparent layer to seal the surface. A classical work might take weeks or even months to layer the paint, but the most skilled early artists, such as Jan van Eyck, also used Wet-on-wet painting for some details. Artists in later periods such as the impressionist era often used this more widely, blending the wet paint on the canvas without following the Renaissance layering and glazing method. This method is also called "Alla Prima." When the image is finished and dried for up to a year, an artist would often seal the work with a layer of varnish typically made from damar gum crystals dissolved in turpentine. Contemporary artists increasingly resist the varnishing of their work, preferring that the surfaces remain varnish-free indefinitely.

Panel painting is very old; we know it was a very prestigous medium in Greece and Rome, but only very few examples of ancient panel paintings have survived. A series of 6th century BC painted tablets from Pitsa (Greece) represent the oldest surviving Greek panel paintings. The first century BC to third century AD Fayum mummy portraits, preserved in the exceptionally dry conditions of Egypt, provide the bulk of surviving panel painting from the Imperial Roman period - about 900 face or bust portraits survive. The Severan Tondo, also from Egypt (about 200AD) is one of the handful of non-funerary Graeco-Roman specimens to survive. Panel painting has always been the normal support for the Icons of Byzantine art and the later Orthodox traditions, the earliest of which (all in Saint Catherine's Monastery, Mount Sinai) date from the 5th or 6th centuries, and are the oldest panel paintings which seem to be of the highest contemporary quality. Encaustic and tempera are the two techniques used in antiquity; encaustic largely disappears after these early Byzantine icons.

In the late 12th century panel painting experienced a revival in Western Europe because of new liturgical practices—the priest and congregation were now on the same side of the altar, leaving the space behind the altar free for the display of a holy image—and thus altar decorations were in demand. The earliest forms of panel painting were dossals (altar backs), altar fronts and crucifixes. All were painted with religious images, commonly the Christ or the Virgin, with the saints appropriate to the dedication of the church, and the local town or diociese, or to the donor. The donor and members of his family are also often shown, usually kneeling to the side.

Italy in the 13th and 14th centuries was a great period of panel painting, mostly altarpieces or other religious works. However, it is estimated that of all the panel paintings produced there, 99.9 percent have been lost. The vast majority of Early Netherlandish paintings are on panel, and these include most of the earliest portraits, such as those of Jan van Eyck, and some other secular scenes. However, one of the earliest surviving oils on canvas is a French Madonna with angels of about 1410 in the Gemäldegalerie, Berlin, which is very early indeed for oil painting also.


The Frankfurt Paradiesgärtlein, a German panel painting from circa 1410.

By the 15th century with the increased wealth of Europe, and later the appearance of humanism, and a changing attitude about the function of art and patronage, panel painting went in new directions. Secular art opened the way to the creation of chests, painted beds, birth trays and other furniture. Many such works are now detached and hung framed on walls in museums. Many double-sided wings of altarpieces (see picture at top) have also been sawn into two one-sided panels.

Canvas took over from panel in Italy by the first half of the 16th century, a change led by Mantegna and the artists of Venice (which made the finest canvas at this point). In the Netherlands the change took about a century longer, and panel paintings remained common, especially in Northern Europe, even after the cheaper and more portable canvas had become the main support medium. The young Rubens and many other painters preferred it for the greater precision that could be achieved with a totally solid support, and many of his most important works also used it, even for paintings over four metres long in one dimension. His panels are of notoriously complicated construction, containing as many as seventeen pieces of wood (Het Steen, National Gallery, London). For smaller cabinet paintings, copper sheets (often old printmaking plates) were another rival support, from the end of the 16th century, used by many artists including Adam Elsheimer. Many Dutch painters of the Golden Age used panel for their small works, including Rembrandt on occasion. By the 18th century it had become unusual to paint on panel, except for small works to be inset into furniture, and the like. But, for example, The National Gallery in London has two Goya portraits on panel.

Many other painting traditions also painted, and still paint, on wood, but the term is usually only used to refer to the Western tradition described above.


Panel construction and preparation

Russian icon by Andrey Rublev, early 15th century, on a three piece panel. The raised edges are probably gesso rather than woodThe technique is known to us through Cennino Cennini's The Craftsman's Handbook (Il libro dell' arte) published in 1390, and other sources. It changed little over the centuries. It was a laborious and painstaking process:

A carpenter would construct a solid wood piece the size of the panel needed. Usually a radial cut piece was preferred (across rather than along the length of the tree; the opposite of most timber cuts), with the outer sapwood excluded. In Italy it was usually seasoned poplar, willow or linden. It would be planed and sanded and if needed, joined with other pieces to obtain the desired size and shape.
The wood would be coated with a mixture of animal-skin glues and resin and covered with linen (the mixture and linen combination was known as a "size"); this might be done by a specialist, or in the artists studio.
Once the size had dried, layer upon layer of gesso would be applied, each layer sanded down before the next applied, sometimes as many as 15 layers, before a smooth hard surface emerged, not unlike ivory. This stage was not necessarily done after the 16th century, or darker grounds were used.

Painting techniques

Landscape with rainbow 94 x 123 cm, 1636-8. A large Rubens panel painting, with a panel made out of many piecesOnce the panel construction was complete, the design was laid out, usually in charcoal.

The usual ancient painting technique was encaustic, used at Al-Fayum and in the earliest surviving Byzantine icons, which are at the Saint Catherine's Monastery, Mount Sinai. This uses heated wax as the medium for the pigments.

This was replaced before the end of first millennium by tempera, which uses an egg-yolk medium. Using small brushes dipped in a mixture of pigment and egg-yolk, the paint was applied in very small strokes. Because tempera (like encaustic) dries quickly and is not conducive to mistakes, each stroke had to be perfect each time. This exacting perfection shaped the nature and style of the art produced.

By the beginning of the 15th century, oil painting was developed. This was more tolerant, and allowed the exceptional detail of Early Netherlandish art. This used a very painstaking multi-layered technique, where the painting, or a particular part of it, had to be left for a couple of days for one layer to dry before the next was applied.


Conservation and scientific analysis

Wood panels, especially if kept with too little humidity, often warp and crack with age, and from the 19th century, when reliable techniques were developed, many have been transferred to canvas or modern board supports.

Wood panel is now rather more useful to art historians than canvas, and in recent decades there has been great progress in extracting this information - and many fakes discovered and mistaken datings corrected. Specialists can identify the tree species used, which varied according to the area where the painting was made. Carbon-dating techniques can give an approximate date-range (typically to about a range of about 20 years), and dendrochronology sequences have been developed for the main source areas of timber for panels. Italian paintings used local or sometimes Dalmatian wood, most often poplar, but including chestnut, walnut, oak and other woods. The Netherlands ran short of local timber early in the 15th century, and most Early Netherlandish masterpieces are Baltic oak, often Polish, cut north of Warsaw and shipped down the Vistula, across the Baltic to the Netherlands.[1] Southern German painters often used pine, and mahogany imported into Europe was used by later painters, including examples by Rembrandt and Goya.

In theory dendro-chronology gives an exact felling date, but in practice allowances have to be made for a seasoning period of several years, and a small panel may be from the centre of the tree, with no way of knowing how many rings outside the panel there were. So dendro-chronological conclusions tend to be expressed as a "terminus post quem" or an earliest possible date, with a tentative estimate of an actual date, that may be twenty or more years later.

Canvas
Etymology

The word canvas is derived from the Latin word for cannabis -- hemp was popularly used to make canvas.

The online etymology dictionary shows a more expanded etymology [1]:

1260, from Anglo-Fr. canevaz, from O.Fr. canevas, from V.L. *cannapaceus "made of hemp," from L. cannabis, from Gk. kannabis "hemp," a Scythian or Thracian word. PGT


Physical characteristics

Modern canvas is usually made of cotton. It differs from other heavy cotton fabrics, such as denim, in being plain weave rather than twill weave. Canvas comes in two basic types: plain and duck. The threads in duck canvas are more tightly woven. In the USA, canvas is graded two ways: by weight (ounces per square yard) and by number. The numbers run in reverse of the weight; so, number 10 canvas is lighter than number 4.


Canvas for painting

Canvas has become the most common support medium for oil painting, replacing wooden panels. One of the earliest surviving oils on canvas is a French Madonna with angels of about 1410 in the Gemäldegalerie, Berlin, which is very early indeed for oil painting also. However panel remained much more common until the 16th century in Italy and the 17th century in Northern Europe. Mantegna and Venetian artists were among those leading the change; Venetian sail canvas was readily available and regarded as the best quality.

Canvas is usually stretched across a wooden frame called a stretcher, and may be coated with gesso before it is to be used; this is to prevent oil paint from coming into direct contact with the canvas fibers, which will eventually cause the canvas to decay. A traditional and flexible chalk gesso is composed of lead carbonate and linseed oil, applied over a rabbit skin glue ground; a variation using titanium white pigment and calcium carbonate is rather brittle and susceptible to cracking. (Of course lead-based paint is also poisonous so care has to be taken in using it.) Various alternative and more flexible canvas primers are commercially available, the most popular being a synthetic latex paint composed of titanium dioxide and calcium carbonate, bound with a thermo-plastic emulsion. Notwithstanding the concern for deterioration of materials, many modern artists, such as Jackson Pollock, Kenneth Noland, Francis Bacon, Helen Frankenthaler, Dan Christensen, Larry Zox, Ronnie Landfield, Color Field painters, Lyrical Abstractionists, and others sometimes paint onto the unprimed, or "raw canvas".

Early canvas was made of linen, a sturdy brownish fabric of considerable strength. Linen is particularly suitable for the use of oil paint. In the early 20th century, cotton canvas, often referred to as "cotton duck", came into use. Linen is composed of higher quality material, and remains popular with many professional artists, especially those who work with oil paint. Cotton duck, which stretches more fully and has an even, mechanical weave, offers a more economical alternative. The advent of acrylic paint has greatly increased the popularity and use of cotton duck canvas. Linen and cotton derive from two entirely different plants, the flax plant and the cotton plant.

One can also buy small, prepared canvases which are glued to a cardboard backing in the factory, called "canvas board". However, these are only available in certain sizes, and are not acid-free, so their lifespan is extremely limited. They are usually used for quick studies. Gessoed canvases on stretchers are also available. These pre-stretched, pre-primed canvases are suitable for all but the most exacting professional standards. They are available in a variety of weights: light-weight is about 4 oz. or 5 oz.; medium-weight is about 7 oz. or 8 oz.; heavy-weight is about 10 oz. or 12 oz. They are prepared with two or three coats of gesso and are ready for use right out of the package. Artists desiring greater control of their painting surface often add a coat or two of their preferred gesso. Professional artists who wish to work on canvas may prepare their own canvas in the traditional manner.

One of the most outstanding differences between modern painting techniques and those of the Flemish and Dutch Masters is in the preparation of the canvas. "Modern" techniques take advantage of both the canvas texture as well as those of the paint itself. A novice artist often finds it nearly impossible to approach the realism of such classic art, despite skill in applying the paint. In fact, Renaissance masters took extreme measures to ensure that none of the texture of the canvas came through. This required a painstaking, months-long process of layering the raw canvas with (usually) lead-white paint, then polishing the surface, and then repeating. The final product had little resemblance to fabric, but instead had a glossy, enamel-like finish. Though this may seem an extreme measure to the modern painter, it is crucial if photographic realism is the end goal.

With a properly prepared canvas, the painter will find that each subsequent layer of color glides on in a "buttery" manner, and that with the proper consistency of application (fat over lean technique), a painting entirely devoid of brushstrokes can be readily achieved.

To un-wrinkle the material, use a warm iron (not a hot iron) over a piece of wet cotton to flatten the wrinkles, although hot water on the back works just as well.

Canvas can also be printed on digitally to create canvas prints. After printing, the canvas can be wrapped around a stretcher and displayed.


Splined canvas, stapled stretched canvas and canvas boards

Splined canvasSplined canvases offer advantages that the traditional side-stapled canvas does not. The most obvious is that the edges of the stretched canvas are staple-free. This allows the painter to incorporate painted edges into the artwork itself. It also allows the artwork to be displayed without a frame. Splined canvas is easier to restretch. It's far easier to remove from the stretcher bars (just pull the spline out) and is easier to attach to another support since there is more fabric at the back to work with. Additionally, there are no unsightly staple holes to deal with.

Stapled canvases stay stretched tighter over a longer period of time, but are more difficult to re-stretch when the need arises.

Canvas boards are made of cardboard with canvas stretched over and sealed on the backside. The canvas is typically linen primed for a certain type of paint.


Non-traditional uses for stretched canvas
It has become popular to use the myriad of stretched canvas's sizes and shapes for unconventional creative expression. Artists create miniature works on business card sized stretched canvas and use them as trading cards to make connections with other artists. Many artists use canvas for altered art pieces as well as for scrapbook pages—because stretched canvas is available in many sizes, from miniatures to wall size, it is used for decoupage and needlework projects, made into lamps, or painted simply for home decor.