Everything You Need to Know About Glazing Oil Paintings

One of the most asked about techniques in oil painting is glazing! Old masters like Vermeer used it to achieve luminous skin tones, but there are many other uses for this method and also advantages to using it, too. First let's define what it is:

What is the Glazing Technique in Oil Painting?

A screenshot from Lesson 6 of Foundations of Oil Painting, with glaze applied to much of the painting. You can still see the grisaille in the mouth/jaw area and below.

Glazing means using transparent color over a dried paint layer. Usually this transparent color is relatively dark without the use of white or other light colors. However, this is a technicality: Glazes in the purest sense don't use white, light, or opaque colors, but that doesn't mean there isn't a time and place for them in combination with glazing.

We'll talk more about these variations, but let's focus first on why you might want to use this method and how to get oil paint to be transparent.

What are Advantages to Glazing an Oil Painting?

If you're using an underpainting like a grisaille, glazing transparently can help you retain your drawing and values that you've already established, as opposed to opaque paint which might cover up all your hard work. It's not necessary to glaze over monochromatic paintings, though: You can glaze over color as well!

When you use transparent oil paint, more light is allowed to bounce through the layers of paint. This creates luminosity as light travels through the color, bounces off lighter opaque paint underneath, and then passes through the transparent layers again. The effect can be like a stained glass window.

Using glazes can also help you achieve colors that are otherwise impossible. As an example, when you add white to a color it takes some of the chroma (or intensity) away. So, fire engine red becomes pink, and ultramarine blue grays a little. When you glaze, you use the color straight out of the tube, so you're able to use lighter colors behind the paint to illuminate and lighten the value, without taking away the chroma. 

How to Achieve Transparency in Oil Paint

Some oil paint colors are transparent or semi-transparent right out of the tube, so it helps to use these in your glazes when possible. Many brands write on the tube whether a color is transparent, semi-transparent, or opaque, so check your tubes!

Some colors which are typically transparent or semi-transparent include:

• Ultramarine Blue
• Phthalocyanine Turquoise
• Alizarin Crimson
• Quinacridone Rose
• Magenta
• Burnt Sienna
• Yellow Ochre
• Hansa Yellow
• Zinc White

It is not necessary to use transparent colors for glazing, but it does significantly help the process. 

You can also use a little bit of medium (not solvent! We're talking oil, alkyds, etc.) to help the process, but don't use too much. We don't want it to feel like watercolor, or be drippy. The idea is to use the medium to help you spread the paint out thin, rather than applying an abundance of sloshy paint. If you have too much medium, you'll find that the results are pretty streaky and tough to control. The right amount will help you spread out the paint and get an even surface.

To prepare for glazing, you can oil out your painting (more on that below) or you can simply add medium to the paint mixtures on the palette. When adding to paint on the palette, only use enough so that you can see through the paint when you drag the brush across it, and there are no lumps of thicker paint. Try not to use more than 20% medium to paint, because more than that can cause problems in the curing process.

Apply the glaze with a brush, and scrub or wipe off excess if you need it to be thinner, rather than adding more oil.

Another screenshot from Foundations of Oil Painting, all the vessels in this image have been glazed.

How to Oiling Out Your Painting

“Oiling out” a painting means to apply oil or another medium to a dry painting in a thin layer before applying more paint. This can have a couple purposes: Oiling out restores the luster colors (especially dark, rich colors) had when wet that were lost during drying, and it creates a slick surface over which paint can glide. This helps with blending, subtle transitions, and clean edge work.

Always use the least amount of oil possible to achieve the desired effect. Follow these steps to oil out without using too much medium:

• Apply oil with a brush or with your hand. Work the medium into the surface as much as possible so that the existing paint absorbs it.
• Wipe the excess oil off with a clean rag or paper towel.

If you apply oil paint over oiling out and it spreads out like watercolor, you need to wipe more oil off. The oil should make the surface shiny, but there should be no dripping. When paint is applied it should glide on but maintain the shape of the brush stroke.

Variations on Glazing

When glazing, you can 'break the rules' and introduce some opaque paint, dry paint, or light color, and mix methods as needed. There are many techniques similar to or that work well with the same concepts used in glazing.

Scumbling, for example, is similar to glazing in that it uses a thin layer of paint, however it is applied dry and is thinned by using the brush to scrub the paint around rather than adding medium. Also, scumbles tend to be done with a color lighter than the color of the existing layer, whereas glazes are generally darker or more chromatic.  

Scumbling and glazing can be combined. Also, once a glaze is applied, you can “scumble’ into the wet glaze to add lights and other variations. Above you can see a white being applied into the wet glaze layer in the Vermeer copy from the beginning of this article, but only in the lightest passages. This creates a little more opacity in the lightest areas, but keeps the transparency in other areas with more chroma or which are darker.

Somewhere between a glaze and a scumble, here I am using light paint on a painting which has been oiled out to create some atmosphere and fogginess to a scene.

 Resources

If you'd like more in depth study on these topics, you can find both the copy of Vermeer's Girl with a Pearl Earring and the entire demo of the Three Vessels painting in Foundations of Oil Painting, where you'll also learn imprimatura, grisaille, alla prima painting, atmospheric perspective, color mixing, and more.

If you'd specifically like to study portrait painting, here's a course that leads you through imprimatura, grisaille, glazing, opaque painting, and color mixing specifically geared toward skin tones: Portrait Painting in Oil

You can access both of these courses by signing up for an affordable monthly membership! Check out our membership options here: https://www.schoolofrealistart.com/membership