‘Glazing is when we apply a layer, or multiple layers, of transparent colour over an existing part of a painting,’ says Jackie Garner. ‘The initial marks remain visible, but the colour is modified. The effect is similar to thin washes of colour in watercolour, but the colour is usually stronger with acrylic.

‘Glazing relates to velatura, which means a translucent layer or layers of paint. The underlying layer must be completely dry before applying the glaze so each layer retains its own colour. This is known as optical mixing, as the two colours are not physically mixed together. The result is rich, luminous colours that each contribute to the whole.

‘Paint is usually applied with a soft, wide brush. I often use an old nylon flat brush, about an inch wide.’

Uses for glazing techniques

Glazing is a useful technique in several different ways:

  • Start with a monochrome image and use glazes to add colour.
  • Glaze over an existing colour to adjust or correct it.
  • Create a rich, intense background for a portrait or still life.

Glaze medium

You can glaze by diluting a colour with water, but this carries a risk of underbinding, whereby the paint separates as the emulsion becomes too weak to support the pigment.

A better alternative is to use glaze medium, which makes the paint film stronger and increases gloss and transparency.

How to use glaze medium

Simply put a small dollop of medium on your palette and mix a little with the colour. The resulting mixture will be thick enough to retain some brushmarks. As you add more glaze medium, the colour becomes thinner and more transparent.

Other options include diluting the mix by adding more glaze medium, adding a little water (not more than 25 per cent), or using a more fluid form of acrylic colour.

Like many other acrylic mediums, glaze medium looks milky when wet, but dries clear.

If you want to glaze with a secondary or tertiary colour, mix the desired colour first then add glaze medium. It’s more difficult to judge the colour if you’ve added the milky-looking medium from the outset.

A glaze may be removed while it is still wet. Use a clean rag, kitchen roll or brush to dab or brush away unwanted excess. Once dry, the glaze cannot be removed.

Mixing the glaze with a little retarding medium keeps the colour workable for longer.


Glazing techniques - Exercise one

Begin by making a grid with pencil and ruler, with squares the width of your brush and a little space between each square.

Take each colour in turn and paint a line across the grid.

I’ve used my three primaries from the Sennelier Abstract range, alternating a cool and a warm version of each.


Fortunately for this exercise, each primary is transparent, except for cadmium red. Check your tube or a paint chart to see if a colour is transparent or opaque.

Once the initial layer is dry, repeat the exercise with stripes perpendicular to the first.

You will create a range of luminous colours that vary slightly within each square.

Glazing techniques - Exercise two

This time try three secondary colours: purple, orange and green.

Have fun building a mini abstract by repeated overlapping glazes.

Notice how you can build rich darks by layering colours, with each contributing to the final result.

Demonstration: Beetle Mania

Beetle Mania, acrylic on hardboard, (30x30cm)

This demonstration is inspired by the glossy iridescence of beetles, beginning with a line drawing and adding colour with successive glazes.

Top tips
  1. If you don’t have glaze medium, you can dilute your paint with water, but the effect won’t be quite as transparent or luminous.
  2. You will gradually build up the image, without making strong statements too early on.
  3. The painting evolves gradually so it’s a good exercise in creative decision-making and self-discipline.
  4. Be sure to constantly evaluate which areas to glaze and which have sufficient colour.
  5. For my reference material I’ve used a selection of images: sketchbook drawings, historic watercolours and an Egyptian scarab hieroglyph.
  6. You can make the image your own with other insects or different reference material.

Jackie’s reference sketch for the finished painting, taken from a variety of sources