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Sussing Out Solvents

For oil painters solvents are essential to the painting process. Without solvents oil paints couldn’t be thinned, mediums and varnishes couldn’t be made or used, and brushes couldn’t be cleaned. Fortunately, that is not a situation we have to consider because we have plenty of solvents, but with so much choice it can be difficult to know what the difference is between them all, and that’s just why I’ve written this piece!

Turpentine is easily recognised by its strong and aromatic smell, heady with pine. It is an art material with an especially long and strange history which is very much worth mentioning. It has been in production since antiquity, but only began to be used in painting in the fifteenth century. Before then, in ancient times, turpentine was distilled locally in a primitive manner by boiling the fresh resin from pine trees in a vessel covered with a sheepskin laid over it fleece side down. When boiled the volatile liquid would evaporate, condense, and accumulate in the fleece. Afterwards the condensed liquid was squeezed out and kept in an amphora, or something antiquated like that, perhaps a lekythos (yes, I like history!). A more refined process using a still was devised in the 3rd century by physicians in Alexandria. However, these early alchemists did not use the product in the way we do today, rather they used it as medicine. Today’s doctors would most definitely advise against ingesting it all, but for thousands of years, that’s practically all people did. The Romans drank it to treat depression, during the 16th century naval surgeons injected it hot into wounds, and in the 19th century it was a popular choice as a tonic to kill internal worms. In 1821, one doctor ordered a patient afflicted with tapeworms to drink turpentine every few hours! At the same time in the USA (the age of snake oil salesmen), a certain “Wizard Oil” was being sold, claiming to cure “neuralgia, toothache, headache, diphtheria, sore throat, lame back, sprains, bruises, corns, cramps, colic, diarrhoea, and all pain and inflammation”, it was, of course, just turpentine, and you know what? It probably worked! By killing you! 

Undoubtedly, whilst ingesting turpentine certainly does have strong purgative qualities capable of emptying one’s entire gut (not really a good thing anyway), its toxicity, and ability to cause everything from kidney damage to bleeding in the lungs wholly outweighs any short term potential benefit. So please DO NOT INGEST TURPENTINE.

Anyway, that’s the curious history of turpentine very briefly covered, I’m sure there are many more horrors to be discovered. Thankfully, the idea of using turpentine for painting really took off and that is what we are going to explore next. 

Turpentine is the classic artists’ solvent, and being very old it has many names including distilled turpentine, spirit of turpentine, and oil of turpentine, but they are all the same thing, a highly refined essential oil distilled from pine resin. As a solvent, turpentine is oily and ever so slightly viscous. Turpentine evaporates from paint mixtures at an even rate, reducing the chances of colours sinking unevenly when thinned down whilst having more viscosity and a more even drying time means turpentine gives you more colour control when painting. Importantly, turpentine has a very strong solvent action and is the first stop for dissolving various resins and is the key ingredient to all sorts of mediums and varnishes. 

The downsides of turpentine are that it is inflammable and emits vapours which can be irritable to the skin, the eyes, and the lungs of a lot of people, though often these problems can be mitigated by a well-ventilated studio and the use of barrier cream on your hands, and big scuba goggles for your eyes (maybe a bit far…hahaha! Too funny!). The other downside is the cost which is rather more than that of white spirit. It is important to note that whilst there is no difference between say, spirit of turpentine and oil of turpentine, there is a difference between artists’ turpentine and household turpentine which is often less refined and can still contain gummy residue which can stop your painting from fully drying or cause yellowing over time. Artists’ turpentine has been rectified, or even better, double rectified which means the gummy residue in pure gum turpentine has been fully removed. Of course, many painters do use household turpentine for their painting, and this is usually fine as long it is kept in a sealed container and kept away from the light (which can trigger gumminess). The cost of turpentine means that it should be reserved for painting use only. It would be a real waste to use it to clean brushes.

In contrast to turpentine there is white spirit, a petroleum-based solvent distilled from coal. It is more watery than turpentine, but also has a drier presence which means it evaporates more rapidly and unevenly which can lead to colours looking uneven and flat whilst it also doesn’t give you much time to play around with your paints. White spirit can be stabilised as a paint thinner by mixing in a small amount of linseed stand oil. By doing this you help the solvent settle out and evaporate more evenly whilst painting. The good thing about white spirit is that it is much cheaper than turpentine and whilst it can be used for painting, it is best reserved for sketches and practices, and is really just ideal for cleaning brushes and palettes. Importantly, white spirit is not a strong enough solvent to be used in the making of mediums and varnishes. But usefully white spirit, unlike turpentine can be stored for a long, long time without deteriorating. There are pros and cons to everything!

As well as turpentine and white spirit, there is Zest-it, a citrus-based equivalent, which is non-flammable, non-aromatic, and is classified as biodegradable. Zest-it is similar to turpentine because it dilutes natural resins, including dammar, and so can be used to make excellent mediums and varnishes on a par with those made of turpentine, it is therefore an ideal alternative if you find turpentine is affecting your health. Zest-it is also especially good for painting when on holiday, because being non-flammable, it can travel by road, sea, and air. To dispose of the sludge-like remainder after painting the makers suggest putting it into damp sand or soil, where it will gradually biodegrade (you could not do this with the other options). Importantly, whilst Zest-it is non-aromatic and does not affect one’s health its zesty and zippy Valencian orange perfume is rather powerful.

For artists wishing to avoid the strong odours of white spirit, turpentine, or Zest-it, Sansodor, is a low odour solvent for oil painting. Like white spirit, it is petroleum-based, but is of a higher quality as it keeps the paint ‘open’, if anything, for slightly longer than turpentine, about 6-8 hours (meaning a nice, even finish). By low odour, I really mean low odour, you can only smell if you really go close to the bottle (inadvisable).

Another odourless solvent is Gamsol which is an absolutely top quality solvent. Gamsol evaporates evenly and completely without leaving behind any residue like turpentine can (sometimes) and it beautifully thins colours as well as mediums made by the wider Gamblin brand. Gamsol is also safer than turpentine as it does not emit so many vapours. The downside of Gamsol is that it is very expensive, more so than turpentine, so needs to be used very sparingly. 

One final solvent to note is Winsor & Newton Brush Cleaner which is unusual in that it is water-miscible and is excellent at removing dried oil, alkyd and acrylic from brushes.

I hope this has cleared things up for you. For me, there’s nothing more evocative of the artists’ studio than the heavy scent of turpentine. It is undoubtedly an absolute classic, but because I don’t actually paint that much, and I don’t have a studio, its Sansodor for me!


By Ned Elliott