Mineral Spirits

[John Reidy]

I should know this but I must admit my lack of knowledge on this subject.

I have been working under the idea that Turpenoid is an odorless mineral spirit. I have used this in the past for clean up and for thinning a final varnish.

Is this a good idea?

[Michele Rushworth]

It's not the same stuff and I've heard bad things about it.

[John Reidy]

Thanks, Michelle,

What brand do you use?

Anyone else have any opinions on Turpenoid?

[Michele Rushworth]

I use Gamsol mineral spirits because I understand it 's less flammable than other brands.

[John Reidy]

Thanks, again, Michele,

One question regarding Gamsol. I read that it is not compatable when reducing Damvar varnish. I don't use Damvar but I wonder if you have heard the same.

[Richard Monro]

Pick your poison.

Turpentine is a distilled organic fluid obtained by the complex distillation of resin obtained from trees, mainly various species of pine. It is flammable and volatile.

Turpenoid is a distilled mineral spirit usually made from a petroleum base. It is reasonably nonflammable and has low volatility.

Ingesting either is bad. On the inhalant side turpentine is the bad actor.

Being a tree resin like damar, turpentine works well when mixed with damar. Turpenoid does not.

[John Reidy]

Thank you, Richard,

You've expained the difference and the cause very effectively. I appreciate your help.

[Richard Bingham]

A few other points of interest:

Turpentine, strictly speaking is the gum exudations of pine trees. Pure spirits of gum turpentine is the distillate. Rosin is the solid resin which that distillation leaves behind.

Currently, most "hardware store" turpentine is derived from the steam extraction of forest waste products (stumps and limbs) and smells nastily of creosote. This is to be avoided for purposes of oil painting. Good turpentine smells like a fresh pine forest, and in fact most of the "good stuff" goes into the making of all those pine-scented air-fresheners and other similar household products.

Cutting natural resins such as mastic or dammar with petroleum distillates results in a cloudy varnish.

Used as a solvent to control the viscosity of paint or mediums, turpentine has chemical advantages over mineral spirits; combined with linseed oil, turpentine forms hydroxides by absorbing free acids in the linseed oil. Hydroxides draw atmospheric oxygen, causing paint to dry throughout the film rather than only from the "top down" , which one notes when fresh paint "skins over".

In my opinion, mineral spirits is a convenient solvent for cleaning brushes and tools, but is best omitted from paints and mediums. Odorless or not, MS releases volatile hydrocarbons as it evaporates, same as turpentine. Adequate ventilation in the studio and sensible, sparing use of all solvents are necessary for safety. Turpentine is neither more volatile than MS, nor particularly flammable; a lighted match can be extinguished in it.

[Tom Edgerton]

Be careful, though, in this discussion. Inhalants are not the only problem. Turpentine is more toxic and is absorbed through the skin, and mineral spirits are much less of a problem in this regard.

The best discussion of the various solvents is, I think, at the Gamblin site.

--Tom

[Richard Bingham]

Originally Posted by Tom Edgerton

Be careful, though . . .

Absolutely. Painting at the easel, a competent adult will "be careful" enough by dint of reasonable workmanship. Poor ventilation is less obvious, and more insidious. However, it's no more adviseable to drench painting surfaces, tools, brushes and hands with MS than with turps.

Gouache is a better material choice for those terrorized by possibilities of toxicity.

Tom, could you be so kind as to point us to a qualified source of factual information on the toxicity of turpentine? The Gamblin site appears to be a "sales pitch" in the main, and states nothing more substantive than turpentine is "a known respiratory irritant". It goes on to speculate on the misuse of turps by "painters of 50 years ago . . . [who] created huge canvases of oil colors diluted with turpentine".

Further, "Rembrandt used no painting mediums." A statement knowledgeable painters should find at least controversial if not ridiculous. The intent is to convince readers of the adviseability of using Gamblin's proprietary mediums.

Gamblin's market strategy has been to emphasize that their products are non-toxic and ecologically friendly. Certainly laudable aims in themselves, no doubt reflecting a realistic assessment of the sensibilities and anxieties of their customer base. However, they seem insecure enough with that stance that information on the site for the most part evades hard facts, and tends toward hyperbole and unsubstantiated opinions.