A  visit to New York’s, Metropolitan Museum of Art, Old Masters Collection, provides the interested viewer with an opportunity to look closely at pictures painted on wooden panel, canvas, and occasionally, stone or metal. Here, we will refer to their collection and concentrate on the materials, techniques and physical history of European works from north of the Alps, with an eventual detour to Italy, which will be the subject of Part II of this article. The paintings being considered during the 15th-17th century belong to the genre now classified as “easel paintings” – rectangular in format, enclosed in a frame, and intended to hang or stand upright. Some of the very smallest pictures, especially those with a religious subject, might have been kept in a special box with other treasures. Other small pictures were originally diptychs or triptychs: two or three panels hinged together that could stand open during personal devotion and then be folded for transport or storage. Larger pictures, now all too often framed and presented in museums as separate entities, frequently belonged to multi-part structures – usually three parts or more (the latter referred to as polyptychs) – which functioned as altarpieces placed on or above church altars. Increasingly, as the Renaissance progressed, painters produced paintings with secular themes in single-field format, which also became the preferred form for religious pictures.Painting on wooden panels was a medieval practice that continued through the fifteenth century, although it began to disappear during the first half of the sixteenth century (more rapidly in Italy than in northern Europe). Hardwoods were preferred – oak in the Netherlands, and in other regions lime, beech, chestnut, and cherry among others, depending upon local availability. The fashioning of panels and wooden frames was undertaken by specialists: carpenters with their own workshops who were subject to guild regulations mandating high quality for their products, as were the painters in their guild. The wood was to be well seasoned and quarter sawn into planks, which were then joined with wooden dowels, and extra battens nailed to the reverse if the panel was a large one. The planks were usually aligned vertically if the panel was rectangular in shape. Looking closely at a painting on panel today, one may occasionally see the vertical joints of the planks, especially if a crack has opened along one of these seams. 

Panel supports were eventually supplanted by stretched canvas during the later part of the Renaissance, although for centuries past there had been an active industry producing painted works such as banners and wall hangings, often on linen. The canvas supports of easel paintings, of which there are numerous examples in any museum, were most often stretched onto wooden frames, although they could also be glued to panels. As the sixteenth century progressed, a taste developed for paintings on less traditional materials such as slate and copper. The nature of the support affected the finished appearance of the picture because paint layers tended to be fewer and thinner by then, and painters would exploit the roughness and more matte characteristics of canvas or the smooth and shiny surface of copper or slate. In the case of the latter two, the taste for these supports may have been prompted by their resemblance to the brilliantly opaque surfaces of expensive enamels. 

 

Painters had been aware for centuries before this, however, that the color, texture and reflectivity of the ground on which they painted would affect the finished appearance of the painting. Panels were primed before the pigment was applied to create a smooth, non-absorbent and brightly white surface. Upon arriving at the painter’s workshop a panel would receive multiple layers of gesso, ground calcium carbonate mixed with glue (the Italian painters typically used calcium sulfate instead). The first layer might be a piece of fabric glued directly to the panel to help hide seams and knots. Canvas was also gessoed, although the layers were much thinner to avoid cracking. By the sixteenth century the gesso layer could be so thin that it lodged only between the interstices of the fabric weave, allowing the texture of the canvas to play a role in the achievement of painterly effects. By this time many painters had begun to tint their grounds by adding pigments to the gesso, with noticeably darker colors by the end of the Renaissance (ca. 1600). One may occasionally see the color of ground priming when tiny cracks – craquelure – caused by various kinds of damage and wear reveal the under layers. 

The next stage was to apply the composition to the prepared surface. Painters often executed highly finished preparatory drawings, which could be transferred by tracing or pouncing – pricking holes along the contours of the drawing and dusting charcoal through the holes onto the gesso ground. A common method of transferring a compositional motif was “squaring”, which allowed the artist to alter its scale while maintaining the desired proportional relationships. Some painters executed freehand sketches directly, using pen and ink, chalk, or a brush dipped in a diluted pigment; and architectural details were incised with a stylus, although this latter practice was more frequent in Italy. One may occasionally see traces of underdrawing if one looks closely, especially where paint layers have become transparent over time. 

By the Renaissance period many painters were making more than one version of their pictures, especially the smaller ones that could be sold on the open market or customized to suit a client’s taste. It was essential to keep detailed preparatory drawings in the workshop for this purpose. In addition to copies or versions of their own work, ranging from studies of individual heads or hands to compositional sketches for large-scale works such as wall paintings. many painters began to answer the demand for copies of works by “famous” artists. This became an important sector of the painting industry throughout Europe, and the copyists, often reputable painters in their own right, would use prints as their source if an original was not close at hand. 

Netherlandish painters were the first to move from the traditional tempera technique to oil, although the two techniques could be mixed in a single painting, with tempera used for underdrawing and for base layers over which oil glazes were applied, or tempera used for lighter-colored areas and oil glazes for the deeper colors. By the end of the fifteenth century the oil technique had spread to Italy and tempera gradually disappeared. Tempera, defined broadly, refers to all water-soluble binders to which pigment is added, but applied to easel paintings, it usually meant pigment mixed with egg yolk. The paint was painstakingly applied by means of small brushstrokes placed side by side with little blending – the various color hues and values were mixed beforehand and kept in separate containers. Tempera produced a hard and rather shiny finish, which was generally quite opaque. 

The early oil technique was based on glazing, whereby pigments were mixed in walnut or linseed oil (sometimes heat-treated beforehand to speed up the drying time), and applied in relatively thin layers that allowed light to penetrate. Light would reflect off the underlayers, including areas of the white gesso ground, and travel back through the veils of colored glazes. In general, while tempera technique worked from dark to light, beginning with the most saturated hue of a pigment in the shadows and adding lighter mixtures for the midtones and highlights, oil glazing worked from lighter underlayers through successive layers of glaze selectively applied to deepen midtones and then to create the deepest shadows. Needless to say, it is virtually impossible to see any brushstrokes – the painter’s application of paint is entirely hidden. Glaze layers are the first to disappear if a painting undergoes any surface damage, which can alter the hues and color relationships. 

 

Fifteenth century painting technique in northern Europe, most especially in Flanders, was based on the reproduction of minutely-observed details of the material world and on the play of shadow and highlight that enabled the viewer to perceive them. Looking closely at a fifteenth century Flemish painting will reveal the painting of individual strands of hair, the highlights on the tiniest pearl or the transparent sparkle of a drop of water . By the sixteenth century, however, many painters were exploring other possibilities offered by an oil-based technique. In addition to exploiting oil’s translucency, they were experimenting with its opacity and malleability, building up highlights with thick daubs of pure pigment – impasto – and dragging and scumbling small amounts of pigment with a dry brush. The resulting picture surface can be rough and three-dimensional in places when viewed close up, yet from a distance the effects are optically convincing and often quite spectacular. This painterly approach was championed from the sixteenth century on by such famous painters as Titian, Rubens and Rembrandt and, in the nineteenth century by Corot and Degas, among others. 

The pigments used by European painters, north and south of the Alps, changed very little until the invention of synthetic pigments in the eighteenth and nineteenth centuries. Pigments were derived from inorganic materials, mostly minerals, that often had to be refined or synthesized with other ingredients to produce colorants such as red and white lead, vermilion, lead-tin yellow, the blues of azurite and lapis lazuli, various colored “earths”, and copper greens. Other pigments were derived from organic sources: black from burned wood, oil or bone; greens, yellows, reds and blues from plants or insects. The latter often produced highly prized red dyes that were turned into pigments by extracting the color from previously-dyed fabric. Gold, silver and tin were all used to highlight details such as crowns, swords and embroidery, and especially for elements that were intended to radiate sacred light such as haloes. Gold was the most expensive and the preferred choice. Gold coins were beaten into thin sheets which could then be cut to various sizes and applied, or the gold could be shredded, mixed with a binder and applied with a brush. One often sees a reddish-brown color showing through damaged areas of applied gold leaf. This is a clay called “bole” that was the preferred ground on which to adhere the gold. Its red hue gave the gold an extra fiery glow, and it formed an extra cushion when the gold areas were “tooled”, that is, designs were gently pressed into the leaf with small stylus-like implements bearing geometric shapes on their tips. The taste for using real gold in paintings slowly fell out of fashion. By the sixteenth century the optical effects of metals, jewels, and even rays of light were created with white and yellow paint instead. More value was placed on the painters’ skill at creating optical illusions than on the presence of the real material. 

Framing was the last step in the production of a painting. By the Renaissance period the frame was usually the responsibility of the painter even if he subcontracted the actual construction to a carpenter or sculptor. Frames were often gilded or painted, sometimes with a special technique intended to imitate colored marble. The elaborate frames for large altarpieces in the late Middle Ages and early Renaissance constituted a substantial part of the cost of the finished product, but as picture formats were simplified into the single-field, rectangular format, frames became considerably less important and often considerably less expensive than the image framed. The frames that presently surround older pictures are rarely original. It is only very recently that frames have themselves become objects of study and hence valued. For centuries, pictures were removed from their frames and re-framed according to the prevailing taste. This was easy to do with canvasses and panels with separate frames, but many early panels, particularly small ones that were originally parts of multi-part altarpieces, were constructed with integral frames, either carved from the same wood as the plank or molded out of gesso (often applied over pieces of wood molding nailed to the planks). These framed fragments are ubiquitous in museum holdings of late Medieval and early Renaissance pictures, and are invariably hung as separate and discreet works of art, having lost their original context entirely. 

Looking closely at pictures on museum walls provides us with glimpses of the process by which painters created their works. It also shows us how closely and carefully these painters regarded the world around them and sought to capture its appearances, including, one could argue, even the phenomenon of sight itself. Despite the damage caused by centuries of wear and aging, it is a tribute to the skill of their makers that these objects have survived as long as they have and still retain the capacity to amaze us. 

by Louisa Matthew- Contributing Writer