Glazing is a procedure used by painters since the development of oil painting. Although glazing appears to be very simple on paper, it is a rather complex undertaking in practice. In its simplest form, glazing involves- usually with a brush that is wide and soft- applying a thin layer of paint over another carefully dried layer of thick paint. The dried layer, or under-painting, normally has just one colour, but it may also contain some other colours as well. The two layers of the paint are not necessarily mixed physically, but they are mixed optically. Glazing can be very much likened to placing a foil of coloured acetate over a colourless photograph. The paint used to glaze has to be altered a little bit by an oil medium produce the right flexibility for brushing. What glazing does is that it creates a kind of unique shine through, stained glass effect that cannot possibly be obtained directly mixing the paint.
Glazing is always limited to clear passages of the layout. Shiny coloured clothes were often glazed. Glazing was used essentially for two reasons. First, ancient artists had very few of the bright colours that are available today. For instance, colours such as greens, oranges, and strong purples were either scarce or rocky and had to be combined with available stain. Glazing blue over a reddish underpinning (or vice versa) was approximated for purple. Second, glazing produces an exceptional brightness that is impossible to achieve otherwise. Only naturally transparent stains, called lakes, are adapted for glazing. The primary colouring’s used for glazing were carmine, natural ultramarine, madder lake, and various organic yellow lakes and indigo.
There are, however, many downsides with using glazing. It is tough to predict with certainty the final multicoloured effect of the glazed area in the overall balance of the finished work. Due to the transparent nature of a glazed work, it produces a visual depth that draws the attention of the viewer’s eye more than the surrounding layers of blurred paint which usually covers a greater part of the painted surface of the canvas. Moreover, it is not entirely known how a glaze is to be applied: one has to determine with maximum accuracy, how thick or thin the glaze-paint should be: a little too revealing or a tad too excessive an application can change the paint layer’s colour or tonal value to an important degree. Same can be said of the under-painting which is usually brought to its final point of detail- once the under-painting is glazed, it can no longer be amended easily. These were the reasons why glazing was not used for anything other than very distinct areas of the painting.
These days, there are studies that make reference to the glazing technique in the paintings of Vermeer. However, Vermeer’s use of glazing tend to be overstated by art historians and do not usually differentiate between glazing used a way of making corrections – light glazes that are meant to change the underlying paint layer slightly which had failed to meet the painter’s original expectations – and real glazing, which, instead, wishes to create by plan an explicit and a pictorial effect that is otherwise unbelievable. Although this distinction might not seem important, the idea that Vermeer built up his paintings in successions of glazes is incorrect and often creates an inaccurate perception of Vermeer’s painting methods. Glazes usually attract dust due to their high oil content. For this reason, Dutch painters like Vermeer used glazing selectively according to well-known formulas.
One well-preserved example of glazing can be found in Vermeer’s “Girl with a Red Hat” painting. Various stages of the 17th-century multi-stage painting process can be observed in the reconstruction to the left. The red hat, in line with common practices for painting bright red objects, is first designed with shades of pure vermilion and black. Afterwards, once the under-painting is well dried, the lighter areas will then be glazed with thin layers of pure madder lake while the shadowed areas would be expanded with a thicker glaze of madder lake and, probably, some black.
The background drapery is smartly effected with the so-called wet-in-wet technique using several earth colours and natural ultramarine. Still, in the under-painting stage, the blue satin garment is modelled with raw brown and small about of white in the highlights.