In truth, the basic principle of glazing in oil painting is easy to understand, although it is a painting technique that requires patience, since it is necessary to wait until each layer is completely dry before applying the and a good knowledge of the colors you are using, in order to "predict" the result of the glaze. This is mainly why beginners do not know for a long time the technique of glazing and the fabulous results it can bring.
Glacis is the name used for a thin layer of transparent paint, mainly in oil paint and acrylic. Glazes are used on top of each other to create depth and change colors in a painting. A glaze must be completely dry before applying another on top, so as not to mix the colors.
Each shade of glaze changes the color below. When you look at the painting, the color is optically blended, resulting in deep and rich colors. For example, painting a glaze of red on a blue gives a richer purple than if you mixed red and blue on your palette before applying it.
To simplify the scientific explanation behind this phenomenon: the purple you see is created by light reflecting from the canvas through the blue layer, then from the red layer, into the eye, producing a deeper color as if she had thought from a single coat of paint.
It is not absolutely necessary to use the glazing technique. For example, for our reproductions in normal quality, we do not use it and have very good results. But, it is a technique that should not be dismissed until you have spent some time in it, because it gives spectacular results. The terms "shiny" and "luminous" are commonly used to describe the effect.
A glaze is a single layer of a single color. How many layers you can use depends on the result you want to achieve and comes with experience. Glazing works best if you use just one pigment per coat, not a mixture of two or more. The more pigments you use, the faster you will achieve a brown or gray (tertiary colors).
Using a paint color that contains a single pigment rather than a mixture also makes it easier to predict the effect layering will have, helps control saturation, and reduces the risk of creating dull colors.
Pigments in paint are classified as opaque, semi-transparent or transparent.
You can use opaque colors for a glaze - the result just isn't the same as with transparent colors. We use it, for example, to reproduce a hazy effect when painting a picture with fog.
Glazing in oil paint is a fabulous technique, which gives excellent results. We mainly use it for our luxury online painting reproductions; this is also why the realization takes more time.