Oil painting mediums and solvents like Liquin, Maroger, Venice Turpentine, Gamsol, or Oleogel are used by tens of thousands of artists around the world.  If we’re wanting to be toxic-free in our studios (solvent-free) what mediums are safe to use – both for our personal health and for the health of our paintings? Is it necessary to use mediums? How do we get those wonderful Richard Schmid type initial washes without using mineral spirits (is it even possible)?

I am going to talk about that today in the video below and throughout this post. I will also discuss what I consider best practices for the use of oil painting mediums and solvents.

My Recommendation for the use of Mediums and Solvents

Before we go into some detail about some of the popular oil painting mediums and solvents let me tell you my recommendation. Use paint straight from the tube only, as much as possible. Stick with linseed or walnut oil as a medium when you need a little punch to the fluidity of your paint (or a solvent-free medium). Use high-quality paints – not student grade.

With all mediums use them sparingly!

Stay away from mediums and solvents if you can. And when you feel it is necessary to use something like Gamsol mineral spirits, use it only in small amounts.

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Toxic-Free Mediums

Oil painting is a non-toxic pursuit. As long as you don’t eat, spray, or sand the paint, you never have to worry about the toxicity of oil paint. The heavy metals and pigments in oil paint will not absorb through your skin.

If you are not allergic to oils, like linseed, walnut or poppyseed, you will not be harmed by oil paint. There are no fumes or VOC’s. There is nothing harmful about oil paints even in an enclosed studio.

Walnut oil - M Graham and Company

Walnut oil – M Graham and Company

The trouble comes from solvents and mediums that many artists use. They leak harmful fumes into the air and some can be absorbed through your skin.

The best toxic-free mediums I am aware of are the oils themselves – linseed, walnut, or poppyseed, but it depends on the particular effect you are after. Safflower, sunflower, and others are usable, but they generally do not dry to as hard and tough of a paint film. Oils should be used sparingly so the paint doesn’t become too fat, especially in the lower layers of paint, otherwise, it might cause wrinkling, cracking, and excess yellowing. Why? If the upper layer dries faster than the lower layer then the lower layer may cause the upper layer to stretch and then contract which causes wrinkling and the possibility of cracking. The yellowing effect seen in oil paints is from the oil binder – more oil often equals more yellowing. That’s why glazes should be left to the final stages if possible. Of course, most of the problems associated with excess oil in the early stages don’t apply when painting Alla Prima (wet-into-wet).

If you want to experiment with other ‘safe’ mediums, watch for those that do not contain petroleum distillates. Mineral spirits is a petroleum distillate that is often used in mediums.

Oleogel is one of the few I have found that is completely non-toxic (just don’t eat it). It does not contain driers like alkyd mediums (they do make an alkyd version). Alkyds make the paint film tougher, but also are thought to make them more brittle which may, in turn, crack excessively in the future. When I talked to George at Natural Pigments he told me Oleogel will not change the characteristics of oil paint. The mark-making remains the same. It can make the paint more transparent without thinning the paint – avoiding the limitations of just using oil since the silica adds strength. The density of the paint can be thinned or remain thick depending on how much you work the paint because it is thixotropic (think of sand at the beach – it remains solid to walk on unless you agitate it and make it more fluid by bringing water to the surface). That thixotropic character allows it to be used for both thin glazes and for thick impasto.

Oleogel non-toxic oil painting medium

Oleogel non-toxic oil painting medium

 

Supposed “Old Masters’ Mediums and Solvents

Turpentine was used for hundreds of years. It is not a petroleum product like mineral spirits, it comes from tree resin (balsam or sap). There are two general types of turpentine used in oil painting: the refined turpentine solvent and the unrefined balsam (like Larch Venice or Venetian Turpentine). The solvent is highly toxic. It emits aromatic fumes (hydrocarbons) that are extremely harmful, and it can absorb through the skin bringing heavy metals from paints with it into your body. Don’t use mediums that require turpentine! Turpentine weakens the paint film as well as our health.

Larch Turpentine (or equivalent) is thick and not refined, but most contain some refined turpentine. Tree resin mediums are best avoided unless you have a critical technique you use that demands it. Larch turpentine, Canadian Balsam, Venice Turpentine, Dammar and any other soft (or hard) resin weakens the paint film compared to oil paint straight from the tube.

Maroger medium is a favorite of art legends David Leffel and Sherrie McGraw. If they use Jacques Maroger’s Rubens, Italian, or Venetian Mediums then they probably contain a mixture of some or all of mastic, linseed oil, leaded oil (black oil), turpentine, and wax – definitely toxic and not good for the oil paint film strength. Also, conservators have found no evidence to support the use of Maroger or Megilp mediums by Rubens. His paintings show evidence of the opposite scenario – the oil paint film without those mediums is much stronger and solvent resilient compared to those like Turner who used mediums like Megilp.

Spike oil (lavender oil) is not recommended. It is used as a painting solvent or medium much like Turpentine or mineral spirits. I tried it out and it quickly caused a flushed feeling in my skin and gave me a headache. I have also read that it weakens the paint film compared to straight paint.

Spike Oil by Rublev used as a painting medium

Spike Oil by Rublev (Natural Pigments) used as a painting solvent or medium much like Turpentine or mineral spirits

 

Modern Mediums and Solvents – NOT Toxin-Free

Mediums and solvents are used to add more gloss, less gloss (matte), make paint thinner or to add impasto thickness. They can be low viscosity (fluid like water) and high viscosity (thick like syrup). There are also gels that help extend paint or add luminosity while keeping the brush texture. Let’s discuss a few of them.

Gamsol is the least toxic mineral spirits I know of. They have removed almost 100% of the aromatic hydrocarbons that are the most harmful part of solvents. It still causes problems with some artists though, and emits fumes (although, the fumes seem to be harmful only to those with extreme sensitivity to chemical fumes). As with all things on this earth, some artists are more sensitive than others. If you find you can’t live without it, then make sure your studio is well ventilated or use it mostly outdoors. Gamblin wrote an interesting article about the use of mineral spirits in schools and the non-toxic nature of Gamsol here: https://gamblincolors.com/studio-safety/guideforschools/

Alkyds are generally fast-drying mediums. Most are toxic to some degree (I’m not sure of any that are not). Some of the leading alkyd mediums are Winsor and Newton Liquin, Gamblin Galkyd, Gamblin Solvent Free Gel, and M Graham Walnut Alkyd. Alkyds can be used as a medium during Alla Prima (wet-into-wet) painting as well as for glazes. I don’t like them because they are generally sticky – I like the smoother flow of straight oil paint. The long term effects on paintings are not known since they have only been in wide use since about the ’60s. Some research suggests that alkyds make the paint film stronger, but also potentially more prone to cracking.

Alkyds should never be used for varnishing a painting because they cannot be easily removed (if at all) for cleaning purposes (the reason for varnish).

You may hear artists talk about Liquin as a non-toxic medium – it is not non-toxic. It is made with petroleum distillates. Now, some may not be affected by Liquin at all. For others, however, I have read that consistent use over several years caused lung and skin problems such that when they used Liquin they suffered and when they stopped using it the problems stopped. If you’ve been using Liquin and love it, then follow what you think is best for your art. My recommendation still stands – use it sparingly. It will not make the paint film last longer – the paint is better without it (probably – not enough studies to know for certain). But, for some artists they love the effects they get from it (it will cause a satin sheen, slightly de-glossing the typical oil paint luminosity which is why I only used it for a short time in the ’90s).

Conclusion

If you’re going to use a medium, alkyds are probably the least harmful to the paint film (as far as we know at this time) compared with soft and hard resin-based mediums like Damar.

Oleogel looks like it might offer the best option for adding some fluidity to paint for early washes, maintaining the gloss and brush-mark benefits of oil paints, and not being toxic. As with all mediums, use it sparingly.

To see links to the products I use like solvents and paints go to the blog post: Art Supply List