Solving the Solvent Problem
Dangerous chemicals can wreak havoc on our bodies. Here's how to avoid some of them when painting.
Years ago, as an illustrator, I was painting a castle in the mountains for a book cover, when I began to sneeze. Within minutes, my entire head had become a mucous machine and my head was pounding. I thought I had caught the worst cold ever.
Turns out, that one of my favorite painting mediums, Copal, had undergone a shift in composition. They had created a synthetic version instead of using the traditional tree resin. I had just gotten a new bottle, and I was very allergic to this new chemical compound.
It took me a while to discover what the cause was, and many years before I learned the reason why I suddenly developed an allergy to Copal Painting Medium. I eventually gave up oil painting for a variety of reasons, but before I did, I learned a lot about the stuff. Here’s a run-down of what I know about the dangers of solvents and mediums, based on experience and memory of past research. I think everything is pretty accurate, but I’m using my own terminology. Don’t get made if I say something different than what you have learned. Comments are welcome!
There are 4 basic kinds of oils:
1. Permanently viscous - never “dries”
Avoid these with painting (includes many cooking oils)
2. Volatile - evaporating
Includes oil solvents, and is used for cleaning, thinning, and making washes with bleed-blending. Common solvents are turpentine, mineral spirits, and paint thinner, and these will evaporate out quickly, turning from liquid into gas, and filling the surrounding atmosphere. The very thin layer of paint in a color wash that a solvent leaves behind, can lose tackiness much quicker than oils normally do.
3. Oxidizing - hardening
This is the binder for paints, or a medium to mix into the to change consistency or extend. They never actually dry or evaporate out. These oils react chemically with oxygen in the atmosphere to become harder and harder over time. Oxidation for a durable surface hardness takes 3 days to 3 weeks depending on composition of the medium and the thickness of it.
4. Water soluble
A physics-busting chimera, water-soluble oil paints have compounds added to regular Oxidizing oils, that allow water to become a solvent for it. Behavior is slightly different than regular oils and it takes longer to lose tackiness.
More about the most common 2 types of oils for painters
Solvents
All thinners will permeate the air with harmful fumes. Most “odorless” thinners have smell-cancelling chemicals added to make them harder to detect, but the fumes are still there. Gamsol is the best thinner. They remove some of the volatile compounds so it’s a little safer and less smelly. However, we still can’t have it in the studio.
Alternatives to traditional solvents depend on the function you're duplicating: a) thinning for painting washes; b) cleaning brushes and other items.
Using solvents to clean brushes is fast and easy, but has dangerous fumes that are harmful to humans and pets, and are a bigger fire hazard. Another big drawback that's often overlooked, is how hard solvents are on brushes, especially natural bristles. Bristles are damaged by paint thinner style solvents.
Making washes without solvents.
Oils that can evaporate more quickly, but are not dangerous are rare. Lavender spike oil has the properties of #2 and #3 oils and is the only widely available "thinner" to paint washes without solvents that really works like them. (One other alternative is using water based oils and making washes with water. The look and feel is different though.)
The only drawbacks to using lavender spike oil are 1) the cost, and 2) like onions, the vapors can irritate eyes and the respiratory system, but it is fairly mild. Lavender oil is used in aroma therapy.
Cleaning without solvents.
Turpenoid Natural is a brand of citrus based cleaner oil. It's not harmful but is a viscous oil, so it never hardens. So it is only used as the first stage of a two-step cleaning and only after you've finished painting so none gets accidentally mixed into your paints. Turpenoid Natural can be put in a coil jar to clean brushes. Afterwards though, the brush needs to be washed with soap to remove the Turpenoid.
It's surprisingly easy to clean brushes during painting using regular oxidizing oils. A small jar - or several - of thin linseed or walnut oil is great for cleaning a brush so you can switch colors. Having two or three jars, going from most dirty, to cleaner ones in succession, allows brushes to be cleaned quickly without the dangers of solvents. This is my recommendation for oil painters who work indoors or without serious ventilation.
After painting, the brushes can be cleaned with Turpenoid Natural and then soap, or just going straight to soap. Hard bars of oil brush cleaner soaps are great for this. The soap can be left in the brush to hold the shape, enhancing the points or edges of brushes. Natural bristle brushes also benefit from hair conditioner treatment, but nylon brushes don't need it.
Oxidizing oils
Linseed oil is the binder in oil paints and is the traditional oxidizing oil. It comes in several consistencies. Sun-thickened is good as a thick medium, and light (thin) can be used to make a kind of wash - but it won’t evaporate out. It has to oxidize before it can be painted over without new layers of paint mixing into it.
ZEC is a thick paste that comes in a tube. It’s a good extender. It doesn't have odor or noticeable fumes.
Other mediums are generally synthetic versions of resins that used to come from trees and plants. These synthetics are much harder on the human respiratory system and should be avoided. Copal painting medium is common, but causes allergic reactions in some people. I have a severe allergy to it.
Many oil painting varnishes are available, and many are synthetic. I don’t have any information on these but I assume they’re using volatile solvents in them. Damar varnish is made from tree resin, and is not synthetically manufactured as far as I know, however, it has volatile solvents in it, making it dangerous to use without adequate ventilation.
Allowed in our studio
Oil pastels
All oil paints and sticks
Linseed oil
Walnut oil (using precautions since some are severely allergic to it)
Lavender spike oil
Turpenoid Natural
Soaps