How to Choose a Finish: What Happens when you Varnish/Glaze an Oil Painting?

glazing or varnishing oil paintings

Do Oil Paintings Need a Varnish or Glaze Finish?

Occasionally I am asked about the surface treatment of Oil Paintings. Should you glaze them? Varnish them? Leave them as-is?

To provide an answer, I’ve put together a video with examples in the form of a Custom Pet Portrait in Oil and one of my Still Life oil paintings.

For each one, we’ll take an up-close look at the surface before and after applying a finish, or glaze, to the oil painting.

Oil Painting Surface Options

The surface of an oil painting can vary a lot. The thickness of the paint,  as well as any medium, thinner or gel used, and the substrate (in other words, what you’re painting on) will all have an effect.

But whether you like the effect comes down to taste. So it’s a good idea to know what your options are.

One option is to use oil paints as they are, right out of the tube.
Another is to change how glossy they are by using additives like a thinner, medium, or gel. And lastly, you can coat the entire surface with a varnish that has a gloss level of your choice.

Untreated, or right out of the tube, oil paints usually dry to a semi-gloss that will stay looking “wetter” than most of acrylics will. Thicker paint will be glossier. Mixing a thinner or medium can adjust the finish of an oil painting up to a high gloss or down to a matte finish, but it won’t be perfectly even. You’ll get some variability in texture because of the uneven thickness of the paint.

A Note on Two Common Oil Paint Thinners:

  • Mixing Mineral Spirits into your paint will make your oil painting finish more matte.
  • Adding Linseed Oil will make the oil painting more glossy.
  • Both will thin the paint so that you can get smoother, longer brushstrokes.

Matte Oil Painting Surfaces

Matte painting surfaces will show the colour and texture of the piece similarly from any angle. An advantage if this is that you won’t get as many “hot spots” where lighting glare stops you from seeing your artwork.

Pet Portrait Painting Surface Matte

You can produce a matte finish in oil paints by using thin coats of paint, as in the above pet portrait. Thin coats allow the canvas substrate to show through even on the areas where the paint is thickest.

Variable Oil Painting Finishes

In the example below, you can see where I’ve used Linseed Oil as a thinner and the surface is glossy. This, mixed with the matte canvas, produces a variable surface.

pet portrait oil painting with linseed oil

Glazed Pet Portrait Surfaces

Glazing oil paintings, on the other hand, makes the surface uniform.

You gain a lot of the benefits of linseed oil, where the colours become more punchy and more vibrant, but you lose some texture along the way.

Some people find this uniformity desirable. But others prefer texture.

This photo shows the pet portrait from the video above after it’s dried over night. From this angle, you can see how uniform the shine of the paint has become.

The Bottom Line on Glazing or Varnishing Oil Paintings

The biggest question you need to ask yourself is what kind of texture you prefer. Glazing is completely a matter of taste.

If you like a uniform surface, maximum colour depth, and don’t mind some glare, a glaze might be for you.

But if you like like the variations that occur in hand-painted work, leave that canvas au-naturel!


Want to See More Oil Painting Examples?

Check out the Canadian Pet Portrait Gallery (or just Dog Paintings or Cat Portraits) Or, sign up for my newsletter below!

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Zann Hemphill

Zann Hemphill is a practising pet portrait artist, writer, and video producer.

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Pet Portrait art of a dog and kitten by Zann Hemphill

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