Oil Painting Medium Recipe
Oil paint straight from the tube has varying consistency so to get your paint to that nice buttery consistency that makes it workable, it may need to be thinned. Ideally you wouldn't do this, as it's better to avoid breaking the paint down at all but the reality is that paint comes out of each tube differently.
To thin oils, some painters just use gum turps (also known as refined turps). This is quick and easy and tends to give a flat or dull finish to the paint. The main problem with using just turps is it can thin the paint out so much that the binder is unable to hold the pigment together, resulting in the paint surface breaking down over time. In fact that's why it has a dull finish, the gloss surface has been broken down and absorbs more light.
If you really love that thinned-out wash-of-paint technique then perhaps acrylics are a better option. Oils are, well... oily and shiny by nature.
So back to the medium...
Basically, there are three things involved in preparing paint for application, the oil paint from the tube, a binder and a volatile solvent (Depending on quality, the paint may already have lots of ingredients in it too but let's forget that for the moment).
You can of course buy a ready-made medium but they generally don't tell you what's in them and it may work out less expensive to mix your own - although I haven't done the calculations on that. I also find something meditative about preparing my own. It's a method of procrastination that feels as if you are doing something art related - anything but actually face the risky business of painting.
The recipe for the medium I use is in the proportions 1:2:5. That is, one part damar varnish, two parts stand oil and five parts refined turpentine.
5 Parts - Gum Turpentine
The turps is the obvious bit, it's the volatile solvent, the stuff it's all mixed in that evaporates off rapidly and leaves the other elements behind.
Oil paint doesn't dry as a result of this evaporation, it drys by a process of oxidation. So the turps is just there to get everything mixed up and flowing.
If you're working from lean to fat, as you should, then you can use this base recipe as the fat mix and pour some off and add more turps for your lean mix for use in earlier layers of painting.
2 Parts - Stand Oil
Stand oil is just linseed oil that has been heated to the point where it's molecular structure changes.
When linseed oil is heated to somewhere around 275-300 degrees Celsius for several hours it polymerises. Something to do with the polyunsaturated fats in the linseed I think. This has to be done in the absence of oxygen too, so probably not something to try at home. Go buy some up at the art shop.
The stand oil in the medium provides elasticity and counteracts the brittle nature of the damar varnish.
1 Part - Damar Mixing Varnish
Damar is resin from trees and is included to give gloss and along with the stand oil, becomes the binder the paint pigment is suspended in after the turps has evaporated off.
You can buy damar resin already been dissolved in turps as a Finishing Varnish for use over finished paintings. A good thing for conservation purposes as it can be removed later with turps. For an oil painting medium the damar and turps are mixed in different proportions as a Mixing Varnish. I buy the damar crystals and mix it with a resin to turps ratio of around 1:1.67.
To avoid a brittle paint finish the total resin content in the final mix, excluding the turps, shouldn't be much more than 15% by volume.
So there's some sort of turps-calc like this...
v = damar mixing varnish solution
d = damar resin
t = gum turpentine
s = stand oil
I'm sure there are many variations people have on this. Feel free to let me know your thoughts in the blog.
Published: 17 March 2007