3 Ways to Thicken Your Oil Paint for Impasto Techniques

Impasto oil painting means to paint with thick paint. Impasto paint will hold the imprint of your brush or palette knife. For oil painters there are a few ways you could add bulk to your paint. This blog post presents some ideas. If you have any others, please let us know by commenting below.

A detail of my painting ‘Blossom’. For this painting I really tried to lay the paint on thick and not blend them at all – placing the paint and leaving it. I did not add any medium to the paint for this painting.

1. Laying on the oil paint in large quantities

The obvious way to thicken your paint is simply to apply lots of it! However it’s also the most costly approach. But it is also the slowest drying. Oil paint hardens as it reacts with air, so if you’ve laid down a thick brush-stroke, the outer layer will harden (and shrink as it does so) while what’s underneath stays wet. This could cause cracking or wrinkling  on the surface as the paint dries. The thicker you lay it on, the more unpredictable the end result.

When I know I will want to paint with thick paint, I squeeze some out on to card a day before. The card draws some of the oil out of the paint. I always keep the boxes my Jackson’s orders come in for this reason!

Top Tip:
It will help to remove some of the oil content of your paint. My favoured way of doing this is to squeeze your paints into blobs on to a piece of card a day or 2 before you’re due to paint. The oil will be drawn out of the paint and turn to a thick, putty-like consistency that is perfect for impasto painting. The painter Peter Clossick describes ‘Tonking’ his paint – blotting the paint with newspaper to get the oil out of the paint – in this blog post here.

Adding marble dust to Oil Paint

2. Adding dry mediums

Painters have been known to add bulk to their oil paint by mixing in dry matter such as sand or marble dust into their paint. The paint takes on a different texture when this is done, losing much of its satin sheen. How fine the dust is will affect how the paint looks. Coarser grit (such as this sand) will show in the paint and make it look crumbly. Fine dust such as marble dust can give paint added elasticity. It will also allow you to get ‘stringy’ effects with the paint when you spread it across your substrate with a palette knife. Derivan Dry Mediums are worth exploring to see what interesting textures can be achieved with your impasto oil paint mixes. This post by Julie Caves shows her findings when she gave them a try with both oil and acrylic.

Thickening oil paint with Michael Harding’s Beeswax Paste. You’ll notice in the bottom left picture that the painto n the right is lighter and softer looker than the paint on the left. This is because the paint on the right has had beeswax mixed with it, which is transparent. As it extends the colour it also increases its transparency. The marble dust is more opaque, and gives the impression of darkening the colour slightly. I was surprised at how different the paint looked after adding these 2 mediums.

3. Adding impasto painting mediums

There are also a number of specially blended mediums intended for impasto effects in oil paint. Beeswax pastes are a traditional and popular choice. It thickens the paint and increases its translucency. The paint tends to look slightly more matte when you use it, and a little crumbly. Beeswax pastes have the added advantage of also having a lovely scent.

If you need something that will dry more quickly, then one of the Alkyd Impasto mediums will serve you well. Oleopasto is a favourite, and will level the brush marks of thick oil paint, while Liquin Impasto lets your brush marks show. There are also some beautiful impasto mediums to explore by Michael Harding, Lukas, Wallace Seymour, Gamblin and others – click here to have a browse.