What is glazing
A glaze is a thin, transparent layer of paint and glazing is building up colour by applying thin, transparent layers one of top of another. This can only be done when the layer beneath is completely dry. Each glaze tints or modifies those beneath it.
Glazing will give you colours with a luminosity, richness, and depth you cannot get by mixing colours on a palette. This is because light travels through all the transparent layers (glazes), bounces off the canvas, and reflects back at you. Your eyes mix the layers of colour to ‘see’ the final colour, giving a luminosity you don’t get with a layer of physically mixed colour.
Transparent colours work best for building up rich, subtle colours through layers of glazes, but this is not to say you shouldn’t experiment with opaque colours. But if you’re just starting to try out glazing, stick to transparent colours and keep opaque colours for the lower layers that will be glazed over. Usually, the tubes of paint will state if it’s transparency.
If you apply a glaze onto paint that isn’t totally dry, the layers of paint will mix together, which is just what you want to happen. 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 and keep a journal to record the findings. The paint must be dry to the touch, not sticky. The trick is to 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. 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-coloured 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. 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. A good rule of thumb is not to use more than 10% water when diluting acrylic paints. It is much better to use a flow medium to change the viscosity of acrylic paint.
Glazes want to be painted smoothly, without visible brush marks. Use a soft brush with rounded edges, such as a filbert brush. A stiff, hog-hair brush can also be used for glazing. Although it’s more economical, it’s not ideal if you’re new to glazing. Flicking over the top of the paint with a dry fan brush is useful way to eliminate visible brush marks.
When the painting is finished, apply one final glaze over the whole painting. This helps unify all the parts of the painting. An alternative is to apply a final unifying glaze to just the elements in the focal point.