Advantages of glazing

• Tones can be adjusted and corrected subtly with glazes, so the artist may feel confident to try a more lively, experimental approach early on in the picture.
• Glazing creates luminous areas of colour. If the undercoat is darker than the glaze, the effect may not be particularly noticeable. However, if the underpainting is lighter or more intense in colour than the glaze, it will glow through, reflecting the light through the translucency of the glaze – an effect that is difficult to achieve in any other way.
• Glazing helps to capture some of the difficult, intense colours in nature, such as the intense red of a geranium, particularly when seen in sunlight. Scarlet pigment, in oil or acrylics, has far less intensity and sun-lit glow than a bright yellow undercolour glazed with a rich transparent scarlet.
• Glazing can adjust the temperature of a passage – changing warm to cool, and vice versa.
• Glazed complementaries on the colour wheel will create sophisticated neutrals.
• Glazed analogous colours – those next to each other on the colour wheel – can add interesting nuances of colour to a painting.
• Glazing will quieten a too-vibrant or garish passage in a painting.
• Glazing enables you to adjust your tones gradually.
• The overall glazing of a painting can pull a picture together, by creating a more unified look.

Mixing a glaze

There is no hard and fast formula – I favour transparent pigments mixed with acrylic medium and water or even just with clean water for small areas. There are various different types of medium, gloss and matt, and flow improver can be used, as can texture gels which increase the transparency of a pigment. Oil painters can try Wingel, a clear, quickdrying gel that is good for glazes and will speed up the drying time of oils.
The proportion of pigment to glazing medium needs testing; with acrylics, a very thin glaze can be achieved with about five per cent pigment, 45 per cent medium and 50 per cent water, but do try different proportions. Most acrylic mediums are milky-white when liquid and only become transparent when dry – a red glaze might look pink until dry, when it will be pure red and transparent. Glazing can also affect surfaces in unexpected ways. I recommend you do not launch yourself into glazing without some practice first.

This feature is an extract from an article by Jackie Simmonds
'To glaze or scumble - that is the question'