Glazing

Glazing was a technique employed  by painters since the invention of oil painting. Although in theory it is very simple, in practice glazing can be a very complex undertaking. In the simplest terms, glazing consists in brushing a transparent layer of paint over another thoroughly dried layer of opaque paint. The underpainting, as the dried layer is usually called, is usually monochromatic but it may also contain color. The two layers of paint are not physically but optically mixed. Glazing is similar to placing a sheet of colored acetate over a monochrome photograph. The paint used to glaze must be diluted by an oil to achieve the correct fluidity for brushing. Glazing creates a unique "shine through" stained glass effect that is not obtainable by direct mixture of paint.

Why Glaze?

Glazing is usually restricted to specific areas of the composition. Bright colored drapery were often glazed. Glazing was basically utilized for two reasons. One, the artist had very few of the brilliant colors that are available today. Strong purples and oranges where not always easy to come by. Purple had to be made by glazing blue over a reddish underpainting or vice a versa. Two, glazing created, as we have said, an extraordinarily luminosity impossible to achieve otherwise. In order to appreciate this effect one has to view the painting directly for no reproduction can convey its jewel-like quality. Only very transparent paints are suited for glazing. The principle pigments used traditionally for glazing were madder lake, carmine, natural ultramarine, verdigris, various organic yellow lakes, and  indigo. For further information on these pigments see Palette.

Glazing, however, has more than one drawback. It is very difficult to accurately anticipate the exact chromatic effect the glazed area will have in the overall harmony of the finished work. It also tends, due to its transparency, to attract the viewer's eye more than the surrounding painted surfaces. It is insufficient to know how a glaze is to be applied, one has to determine with the utmost precision, how thick or thin the glaze-paint should be, a little too scanty or a trifle too lavish an application can change a color or shade to an important degree. The same holds true for the underpainting which must also be brought to its final degree of detail since once glazed it can no longer be corrected easily. For these reasons glazing was not used for other than very specific areas of the painting.

Today there are various very informative studies which discuss glazing in Vermeer's paintings. However, some of them probably tend to overstate Vermeer's use of glazing and do not distinguish between glazing used as a corrective measure - very light glazes meant to alter only slightly the underlying paint layer which for one reason or another had not come up to the painter's original expectations - and true glazing which, instead, aims to create a very specific and otherwise unachievable pictorial effect. This difference might not seem a fundamental one but the idea that Vermeer built up his paintings in a series of successive glazes is incorrect and creates a distorted perception of Vermeer's painting methods. An oil painting cannot be created by a series of successive glazes as if they were water color washes. The bulk of painting in the 17th c. was executed with opaque and semi-opaque layers of  pigment.

Glazes also attract dust due to their high oil content. The particles of dust imbedded in the transparent paint in turn attract pigment in the glaze and ruin the visual effect. Successive glazes only multiply this problem especially in such finely detailed paintings such as Vermeer's. Dutch painters like Vermeer, used glazing very selectively according to well known formulas.

An excellent example of glazing can be found in Vermeer's Girl with a Red Hat. The young woman's  plumed hat was first modeled in vermilion and black. Vermilion, unlike red madder, is a very opaque pigment making it ideal for strong modeling and as can be seen in the image to the right, it has a distinct orange undertone. Once the underpainting was thoroughly dry, it was glazed with madder lake (probably with the aid of a badger brush) to produce the characteristic cherry red. This particular glaze was widely employed by painters since the beginnings of oil painting.