Preparation of the Painting: Support, Sizing and Grounding

Of all 35 (36?) surviving paintings by Vermeer, only two works, Girl with a Flute and Girl with a Red Hat, were not painted on canvas but on thin (oak ?) panels. However, in the artist's death inventory of 1676 there were listed 10 unpainted canvases and 6 unpainted panels in his studio, which indicates that the artist's preference for canvas was not so accentuated as the proportions of his surviving paintings would lead us to believe.

Although canvas as a support for painting was know to the ancients, it became widely used in Italy for oil painting by the end of the 15th century. Until then, both tempera and oil painting had been done primarily on wood panels. The word canvas does not refer to any specific material in the field of textile fabrics, it is applied to number of closely woven materials of relatively course fibers. Linen is preferred for its superior strength. It tears with great difficulty. It is also less hygroscopic than other fabrics that, instead, draw moisture from the air and throw it off upon drying. In this continual expansion and contraction the dry pigment cannot participate, which causes the paint to crack .

Unless treated, canvas is very absorbent and quickly swallows up the oil content of the paint causing it to sink into the fabric. The final chromatic effect of the picture would be impossible to calculate and the roughness of the raw canvas world destroy any illusionistic effect. Canvas must first be properly stretched, sized and grounded before painting.

The Mairrage of Cana, Paolo Veronese
The Marriage at Cana
Paolo Veronese
1563
Oil on canvas, 666 x 990 cm.
Musée du Louvre, Paris

Canvas has various advantages over panel: it is easily transportable, it is far less laborious to prepare, and it can be used to make paintings of far greater dimensions. The Marriage of Cana, the largest known oil painting in the world, measures an astounding 22 x 32 1/2 ft. (666 x 990 cm.).

The tooth and spring of the prepared canvas facilitate a more rapid and expressive execution. It is also possible to effectively use greater quantities of paint and achieve more varied aesthetic solutions. At the same time canvas also permits the painter to obtain fine detail, although not as much as a perfectly smooth panel. Various tones, degrees of roughness and absorption of the canvas can be achieved by altering the materials and preparation methods.

The sizes of canvases may sometimes be associated with local units of measure. The width of a roll of cloth was governed by the width of the 100m: most looms in Twente and Brabant, the main sources for canvas in the Northern Netherlands were two ells (ca. 138 cm) wide, whereas 100m widths of Italian canvases tend to range between 106 and 110 cm. It is now believed that some 17th-century painters bought their canvases ready-made from specialized colormen.

Format and Stretching

Antique strainer
Painter in His Studio, Painting a
Musical Company
(detail)
Jan Miense Molenaer
1631
Oil on canvas, 86 x 127 cm.
Staatliche Museen, Berlin

Vermeer's paintings are often similar in dimensions in different periods of his career. This cannot be due to chance, rather it suggests that Vermeer used standard sizes.1 The 1: 1:14. width to height ratio he generally employed is very nearly square. The square format is the most visually reassuring and stable of all geometrical forms and was used widely in the Netherlands although painters have generally avoided using the perfect square because it tends to have a stifling effect on the expressive content of a work of art.

Over centuries, wood has been the material of choice for the stretchers or strainers used to support the stretched canvases.

Vermeer generally attached his canvas directly on the final stretcher, contrary to the practice of attaching it onto the oversize strainer. This latter method was a widely used and can often be observed in representations of painters in their studios (right). Although this method was employed principally for preparing the canvas, some painters also painted while the canvas was still on the strainer (see detail image left). The function of the oversize strainers must have been to provide a simple and effective way of stretching and restretching slackened canvases. The space between the threads holding the canvas, consolidated by the dry paint, resulted in the traditional scallop appearance of the canvas, exhibiting areas of extreme tension and some intermittent slack. Today's familiar expandable stretchers, which take up the lost tension by means of wedges inserted in the corners, became common only in the 1750s.

Vermeer's Guitar Player, unique among 17th-century canvases, is still on its original strainer with the original wooden pegs used to fix the canvas.

Sizing

animal skin glue
Animal skin glue with water
makes medium strength jelly

Before apply the ground, canvases were first sized. Sizing effectively seals the canvas against the ground and paint layers, both of which contain drying oils that would be damaging if applied directly to the raw canvas. Sizing was made of clippings of rabbit hide, pig-skin or parchment which are sold in the form of thin brittle sheets or course crystallized grains. Size is first soaked in cold water, where it swells considerably. It is then heated in a double boiler until it becomes completely fluid. Animal skin glue must never boil because it will crack shortly afterwards.

The warm glue, about the consistency of honey, is spread on the canvas with a palette knife with quick, energetic strokes so it will penetrate fill up the open pores of the canvas. Size was also employed as a binder for some pigments such as smalt. The presence of animal skin glue can be detected by laboratory analysis for its protein content.

Grounding

After the sized canvas is dry, it is smoothed with a pumice stone, and then grounded. Grounding, or priming as it is also called today, provides the final surface suitable for painting. Grounding must produce a smooth surface that can be easily painted upon, it must be hard but not brittle (which causes cracking), and lastly, it must be porous enough to allow the oil paint to adhere to the canvas .

The Dutch and Flemish often prepared their canvases with two layers of ground, called the Netherlandish double-ground. Generally, the first coating consisted of a mixture of earth pigments. Sometimes this layer may also contain palette scrapings or the sediments from the jar of turpentine used to clean brushes. This produces a dirty grayish color, which may contain a large variety of pigments from the cleansing oil. Its purpose was simply to provide a smooth surface economically. The second ground layer, or imprimatura, usually consisted of a mixture of lead white and carbon black. In order to ensure optical neutrality, small amounts of iron oxide reds or other earth pigments were almost always added to the second coating, thus preventing the so-called "Raleigh scattering," an optical effect which makes a light-toned gray over a darker color appear a harsh bluish gray.

Vermeer generally used light grounds composed of chalk (an inert, inexpensive filler), linseed oil, white-lead and various combinations of earth pigments. For example, the ground of the Woman Holding a Balance contains chalk, white-lead, black and an earth pigment, most likely brown umber. The ground mixture was applied in one layer. The grounded canvas had a warm buff tone that can be seen in various areas of the painting where little or no paint was applied. It would seem that Vermeer prepared his canvas in the conventional manner. There is no evidence that he bought commercially prepared canvases although it is not out of the question.

The Value of Colored Grounds

Painters were aware that the color of the ground influences the perception of the tones and hues of the pigments which are applied to it, especially those used to render shadows, which were generally executed with thin layers of transparent paint. Dark toned canvases greatly aid the rendering of shadowed areas but require repeated layers of lighter paint to represent the strongly illuminated areas.

On the other hand, a ground which is very light obviously does not evidence light tones which painters use in abundance. On a pure white ground any color is darker than the ground allowing the artist to paint in only one direction—from light to dark. Pure white canvas grounds were rarely used until Impressionism because it is very difficult to to create harmony with strongly colored paints of such grounds. Moreover, while on a white ground all tones must be applied deliberately, a tinted ground acts as a middle tone, a sort of tonal safety net. For these reasons neutral or warm light grays were used by Vermeer as well as many other Dutch painters of the time, although he known to have once used a white ground only once at the beginning of his career and a strongly reddish toned in The Love Letter.

Ground material was applied with a sickle-shaped palette knife.

  1. Jørgen Wadum, Vermeer Illuminated. Conservation, Restoration and Research. With contributions by L. Struik van der Loeff and R. Hoppenbrouwers, The Hague, 1994.