Ever since the 15th century, when oil paint first started to become popular as a fine art medium, painters have been using a technique known as "glazing" to create their fantastic colors. Glazing takes a lot of practice to master, but it is not a complex process in an of itself, so with some patience and diligent effort, you can get that same depth and richness in your own paintings!
In Part 1 of this subject we'll look at the history of the glazing technique, how it developed and who some of the major players were, and we'll also delve into the mechanics of glazing with the intention of gaining an understanding of why glazes look so wonderful.
Let's begin with the mechanics. A glaze, by definition, is a thin, semi-transparent layer of colored paint. Typically a small amount of colored paint is mixed with some proportionally greater amount of clear medium to form the glaze, with the exact proportions being dependent on how much of the underlying paint surface you which to see through the glaze. The glazing technique is accomplished by first rendering a monochromatic underpainting, usually with white and another color like burnt sienna, ivory black or green earth. The underpainting should present a rough, sketchy version of the final painting, showing the different forms that make up the composition and presenting basic areas of value that delineate the lights and the shadows. Once the underpainting is COMPLETELY dry, a glaze of a particular color is prepared and then painted over the top of it. Because of the transparency of the glaze layer, the underpainting will still be visible, but it will now be tinted with the hue of the glaze. In most cases it is proper to wait until the glaze layer is dry before applying another one. Each successive layer adds greater complexity and richness to the colors and provides an opportunity for the artist to refine the forms and accentuate the details in the composition. This is just a brief description, we'll get more into the actual step-by-step process in the next chapter of this subject.
So you can probably see already that glazing allows for the creation of very developed and purposeful color schemes because it separates the process into a series of layers and allows the artist to contemplate exactly how much of a particular color to put in a certain area of the painting. Over time, the glazes will build up to create a level of complexity that closely matches that of the real world, which is why glazed paintings can be startlingly photorealistic. In this way, glazing is a technique that can be used to good effect in any painting medium that allows for transparency: oil, acrylic and watercolor being the main ones. However, while glazing is an important technique in both acrylics and watercolors, it is in oil painting that the true majesty of it becomes apparent. The reason for this is because of the physical nature of oil paints which make them different from other media.
Oil paint is essentially pigment mixed with a drying vegetable oil, typically linseed oil, although walnut and poppyseed oil can also be found in certain cases. When oil paint dries, the chemical properties of the oil actually change on a molecular level, becoming a totally different substance from the wet version. This is important because it means that when a wet layer of oil paint is layered over a dry one, the wet layer will stick to the dry one, since it has adhesive properties, but the two will always remain separate layers. With both watercolor and acrylic paint on the other hand, painting one layer over another results in a complete bonding of the two layers that results in one thick layer with stratifications of color. So the secret to the oil painting's beauty is the way that light reflects off the surface of the glazes.
Since glaze layers are translucent, the light passes through them until it reaches the opaque underpainting, then it is reflected back out through the glazes again and goes into the eyes of the viewer. With an acrylic or watercolor painting, the light reacts to the glazes as if they were all one layer, no matter how many layers went into the creation of the color, so it passes through the one layer, reflects off the underpainting and comes back out through that one layer, with the result being one-dimensional (so to speak). With an oil painting, the light passes through each layer as a separate stage before hitting the underpainting, and as the light passes from one layer to the next it becomes slightly refracted resulting in an increase in depth and richness to the color. So, if you have a painting that has three glazed layers on it, the light passes through each of those layers, refracting each time, reflects off of the underpainting and passes back through all three layers again, refracting even more and resulting in a much more complex and realistic looking color.
Now imagine the painting with ten layers of glaze, or twenty! This refraction of light through the translucent layers of glazed color is the secret to why those paintings in the museum look so great and, since this quality is unique to oil paint, it is one of the reasons why oil painting has never been eclipsed by newer varieties of paint like acrylic.
Although oil paint was in use for quite some time beforehand, the peculiar qualities of the glazing technique did not become apparent until the 1400's. The primary medium for painting up until that time was egg tempera, a type of paint that is very opaque and did not lend itself to glazing at all. The early experimenters with glazing still used egg tempera when creating the underpainting, which had it's advantages since egg tempera dries very rapidly. The most famous of these early experiments is the "Arnolfini Portrait" by the Dutch painter Jan van Eyck in 1434. The technique seems to have been immediately and spectacularly successful as is evident from the richness of the colors in this early work by a master artist. The possibilities were not lost on the art world of 15th century Europe and within the next hundred years oil paint came to supplant egg tempera almost completely. With the development and ensuing popularity of canvas as a support, tempera was no longer used even in the underpainting, so oil paint became the dominant painting medium for the next 500 or so years until the invention of acrylic polymer.Next week we'll look at the actual process of how a painting is constructed using glaze layers!
