A glaze is simply a thin, transparent layer of paint and glazing is simply building up the color by applying thin, transparent layers one on top of another, dry layer. Each glaze tints or modifies those beneath it. So why is glazing something that can trouble, and even threaten, artists so much? Well, while the theory may be simple, putting it into practice takes patience and persistence to master.
If you’re a painter who needs instant gratification, glazing is probably not for you. But if you’re a painter wanting to take your paintings up a notch, glazing will give you colors with a luminosity, richness, and depth you cannot get by mixing colors on a palette. Why is this? In very basic terms, it’s because light travels through all the transparent layers (glazes), bounces off the canvas, and reflects back at you. Your eyes mix the layers of color to ‘see’ the final color, giving a luminosity you don’t get with a physically mixed color.
Take the time to learn which pigments are transparent, semi-transparent, or opaque. Some manufacturers state this on their paint tubes (see How to Read a Paint Tube Label), but you can also test for yourself.
Transparent colors work best for building up rich, subtle colors through layers of glazes, but this is not to say you shouldn’t experiment with opaque colors. But if you’re just starting to investigate glazing, stick to transparent colors for your glazes and keep opaque colors for the lower layers that will be glazed over.
If you apply a glaze onto paint that isn’t totally dry, the layers of paint will mix together, which is just what you don’t want to happen. Be patient rather than sorry. If you’re working in acrylics, you can speed up things up by using a hair drier to dry a glaze. How soon an oil glaze will be dry depends on the climate you live in and your studio condition; do some sample glazes to find out. The paint must be dry to the touch, not sticky. Work on several paintings at once so you can move from one to another while you wait for a glaze to dry.
A glaze is a thin layer of paint which should lie smoothly on top of the previous layers. You don’t want it to collect or puddle on any roughness on your support, or rather not when you first start glazing. (It’s something to experiment with once you’ve mastered the basics of glazing.) A smooth hardboard panel or fine-weave canvas is ideal to start with.
Use a light-colored or white ground, which helps reflect light, rather than a dark one, which helps absorb light. If you’re not convinced, do a test by painting exactly the same glazes on a white ground and a black or dark brown one.
Glazing mediums thin the paint you’re using to the right consistency for glazing and, if you buy a fast-drying formula, speed up the rate at which the paint dries. They also solve any possible adhesion problems arising from diluting the paint too much, particularly with acrylics (see How Much Medium Can You Add to Acrylic Paint?). Experiment with the ratio of medium to paint to get a feel for how much to add; too much and you sometimes get a glassy, excessively glossy effect.
Glazes want to be painted smoothly, without visible brush marks. Use a soft brush with rounded edges, such as a filbert brush. You can glaze with a stiff, hog-hair brush, but it’s not ideal if you’re new to glazing. Flicking over the top of the paint with a dry fan or hake brush is a useful way to eliminate visible brush marks.
When the painting is finished, apply one final glaze over the whole painting. This helps to unify all the parts of the painting. An alternative is to apply a final unifying glaze to just the elements in the focal point.