When applying glazes to acrylic paintings, you have two options:

1. water
2. glazing medium.

Is there a benefit to using one over the other? Either will work, but there are distinct advantages to choosing a glazing medium. No matter which base you choose for your acrylic glazes, it’s also important that you mix them properly. You do not want to break down your pigment with too much water​ though a glazing medium can be used in any ratio you desire. Much of this depends on your style of painting and the look you’re going for.

The Benefits of a Glazing Medium

Glazing medium is preferred by many acrylic painters because it maintains or adds to the gloss or matte effect of the paint. These mediums are available in both gloss and matte finish. You will want to choose which works best with the paint you’re using as well as the effect you desire in the painting. The other (and more important) advantage of a glazing medium is that it retains the ‘stickability’ of the paint. The medium contains a binder (or glue) that gives the mixed glaze the ability to stick to the panel or canvas and any underlying layers of paint. Water, on the other hand, can break down the binders that are present in the paint and too much may lead to your paint peeling. You can use a glazing medium with paint in any proportion, adding as little paint as you like for the effect. This is because the medium is like a thin, colourless paint due to that binder.

The Issues with Water for Glazing

Water works fine for glazing up to a point. As mentioned, you do run the risk of the binder in the paint being diluted too much and it loses its ability to stick. Fifty percent paint to water is the general rule. Some paint manufacturers suggest no more than 30 percent water. Artists often don’t pay too much attention to these recommendations, particularly when it comes to glazing. You will know when you have too little paint in your water. If the paint lifts off when you paint over a thin layer with a stiff brush, then you’ve gone too far. It’s very similar to how watercolour paints work.

A Mix of Water and Gloss Medium

If you like, you can also use an acrylic gloss medium along with water to create a custom finish while glazing.

1. An equal proportion of water and acrylic gloss medium will produce a matte finish.
2. As you use a higher percentage of gloss medium, the finish will become more satin-like.
3. A straight gloss medium will, of course, produce a glossy finish.

You can vary these finishes any way you desire for the effect you’re going for in the painting. Also, consider using various finishes to bring out specific properties in certain areas. For instance, you might want a high-gloss glaze over a lake in your landscape and more of a matte or satin look for the pine trees. This approach can produce some very nice effects. As always, if the finish didn’t come out exactly as you planned or you don’t like the final results, you can always add a varnish. They too are available in matte and gloss.

Steps to painting with acrylic glazes

1. Squeeze out a tiny amount of glazing liquid or retarder. You only need to squeeze out the size of a US dime (17.91mm). You can add more as (and if) you run out.
2. Select your main colour, dab some on your brush and swirl it on your palette, loosening up the paint. Add a quick dab of water and/or glazing liquid to increase the fluidity of the paint. In general, you want the paint to be thin, not thick, for it to be a glaze.
3. Select the other colours you’re interested in, and mix them into your main colour. Add more water and/or glazing liquid as you see fit. If the paint seems too thick, keep adding more glazing liquid until your paint is nice and watery.
4. Use a small amount of paint, when making glazes, it goes a long way. The paint is so thin that you can see through the paint to the palette. This is the level of consistency that you are aiming for.

When creating a glaze, what you’re looking for is a mixture that is very fluid and thin. Not thick. So thin it almost looks inconsequential – it makes you think, “How can this tiny amount of paint have any effect on the canvas?” But you’d be surprised – when creating acrylic glazes for photorealist painting, a small amount has a great effect!

 Sometimes the acrylic glazes are very watery, as this creates a very subtle transition. When my acrylic glazes get watery, I lay the painting flat on a table and work on other things until the glaze is completely dry. This is important because if the painting was upright on an easel, the glaze would either flow down (if it’s too runny) or just a part of it would flow down, creating a little pool of intense pigment at the bottom of the area just painted. This isn’t desirable, so it’s best to lay the painting flat. Also, make sure that the glaze is totally dry before you work on it again. If you work on them too soon, you can ruin the glaze and will need to repaint that area. 

If you’re familiar with the properties of watercolours, then you’ll notice that acrylic glazes almost feel like working in watercolour, in terms of the thin quality of the acrylic paint. So if you can get your glazes to resemble the transparent fluidity of watercolors, you’re on the right track!

Of course, not everything you paint will need to be thin and watery. Sometimes you will need strong, bold, thick colours. Rather than load up the brush with lots of paint, I normally paint those areas that require solid, strong colours by building up to them. For example, instead of piling on the black to create a sharp shadow, I add a bit of black, let that dry, then add another bit of black, etc. until it looks finished. Although acrylic paints are very forgiving, it’s still easier to add paint than it is to “subtract” paint – that is, to paint over a mistake you’ve just made.

But if you do make a mistake, don’t worry. You can just paint over the problem area. This is the beauty of acrylics! Sometimes a mistake might be so whopping that it’s distracting and you can’t get your bearings in the painting. If this happens, just paint over the problem area with titanium white or titanium buff and start that area again.

So, to recap: after you paint your underpainting, in which you map out all the important areas of colour, begin working on your glazes. Continue building up these thin, watery acrylic glazes until the image takes form and comes to life!