What solvents are safe for Oil Painting?
With the hot weather this summer in the UK, I became increasingly concerned about using Turpentine (Turps) as a paint thinner and brush cleaner when painting with oils. This is an historically important solvent distilled from pine trees and has a strong (but not unpleasant) odour. It can give some artists headaches but I just found the aroma a bit overpowering in a small room.
But what really caught my attention was the article by Julie Caves on the Jackson Art Website:
I noticed that in the solvent safety table the “flash point” of Turps (the temperature at which a solvent gives off enough vapour to ignite in air in the presence of a spark or flame) is 35 ºC. As the temperature in my studio got to around 35ºC some days, this was a cause of some concern!
White spirit (often used as a Turps substitute) was only a little better with a flashpoint of around 39ºC and has its own hazard problems reported after long-term exposure (including chronic effects on the central nervous system and severe skin irritation).
The table given in the article described several safer alternative solvents with higher flash points so I decided to try some of these.
“Citrus turpentine” is distilled from citrus fruits rather than pine trees and has a pleasant odour with a flashpoint around 53ºC. This sounds safer and useable but, for me, it still had quite a strong aroma in a small room.
Other solvents such as “Studio safe citrus solvent” are composed of less volatile compounds. These are less flammable than turpentine-like compounds and Studio safe citrus solvent is given as “non-flammable”. They have less of a pungent odour and I found the Studio safe orange solvent to have a mild and fairly pleasant orange fragrance.
However, another solvent I tried and now generally prefer is “Zest-it solvent (Citrus Free)” which seems to have very little odour and a flash point of 70ºC. It seemed good both for brush washing and for diluting paint.
From the same manufacturer, I also tried “Clear Painting Medium” for mixing with paint, and liked it because is had more body than the Zest-it solvent alone. It is a mixture of a Zest-it solvent, Linseed Oil (to give it some body) and Orange terpene (a solvent distilled from the zest of oranges with a flash point of about 50ºC). It produces a good combination of paint flow with viscosity and dries with an elastic film that should not yellow.
Also from Zest-it is “Glazing Medium” which is useful for adding thin transparent glazes of oil paint. It is also a mixture, this time with a Zest-it solvent, Linseed Oil and Damar Varnish.
So I have now stopped using Turps and White spirit in favour of safer and less odorous solvents. These can be used for brush cleaning and, when mixed with the very safe Linseed Oil and other terpenes or Damar varnish, give relatively safe painting media that I find are pleasant to use in my studio.
PC Newell September 2019