Sunday, March 4, 2012

Solvent Riddle: Thinners, Turps, Turpentine, Mineral & White Spirit

Our hobby, and the wonderful network of blogs and fora that connects us, is spread clear around the globe. That's something worth celebrating! And so while we all sit down to a nice cup of Assam and a few biscuits, lets consider the impact that our local way of putting things, our vernacular, may have on our selection and use of an important hobby resource.

SOLVENTS
Since I began playing more and more with oil paints, pigments and commercially available enamel based filters and washes I have realised there are a few different common solvents that could be used with these products. Yet around this funny old world of ours the names for these solvents from region to region are easily mistaken or misunderstood.

Now these solvents essentially do the same job, but as they are different, they can have a real impact on our health and on the working properties and finish of what they are mixed with. Understanding these differences and considering that Turps for you, may or may not be Turpentine for me, could help get us closer to the results we hope for.

So lets have another cup of tea and munch a few more biscuits, while we take a look at some of these useful solvents and especially at their names as they appear about the interwebs.

HAZARD NOTE: All solvent vapours are toxic. Even the 'odourless' ones!
DO have plenty of ventilation when you work with this sort of stuff. You need both fresh air coming into your workspace and polluted air going outside. A small fan in a window close to where you work, blowing air out of the room, can be the difference between cool fun and sickness.

TURPENTINE
AKA: Turps, Gum Spirits, Distilled Turpentine, Spirit of Turpentine, Oil of Turpentine, Wood Turpentine, Venice Turpentine

Artists' grade Turpentine is what we want. Its consistency and long drying time can be either advantageous or frustrating. You decide.
Distilled from tree-resins -typically that of pines- pure turpentine is reactive to both light and oxygen and will thicken if not properly stored.

Avoid 'industrial' Turpentine from hardware stores; a poor choice for our work.

Turpentine is a very strong solvent and used in high ratios, or in contact with paint over time, it can break the emulsifying agents that bind your paint. This means that turpentine may not be a good choice if you want to thin and then store a mixture for future use. However, the slight* residue left behind by quality turpentine can be useful for setting pigments, whether you apply the turpentine before, with or after the pigment is up to you.
*Opposed to thick residue left by the cheap stuff!

MINERAL SPIRIT
AKA: Turps, Mineral-Turpentine, White Spirit
Aha! The term 'Turps' leads to some confusion! But it seems to be most widely used to refer to mineral-turpentine, or mineral-spirit; a substitute for turpentine. Here we begin to look at several varieties of petroleum distillate that are intended for a variety of purposes from cleaning-up only, to fine-art finishes.
All mineral spirit is quite fast drying, in fact when working with oil paints, this solvent will be dry long before the binding medium of the paint.This allows you to crack along with your projects fairly quickly.

Again, hardware store grade mineral spirit is not a good choice for our hobby work. While white spirit is also known as paint thinner, we need something that is more refined, and for good reason...

Artists' grade white or mineral spirit is refined to remove contaminants, particularly sulphur, that can react with paint pigments. Even better, the 'Odourless' varieties are further refined to remove more of the toxic volatile aromatic compounds. This is significant given that we tend to work very close to our subjects! These are multi-purpose thinners suitable for all the oil-paint based techniques as well as for the application of pigments.

THINNERS
What's this then? No biscuit for you... A prime example of the sort of term we need to drop from our common hobby vocabulary. It's like some kind of unrevealed secret ingredient. Go ahead and Google 'Thinners', I'll wait here and have another Garibaldi...
What did you find? Nothing specific I'll bet.
When someone does a nice bit of hobby advice and lists thinners as one of the necessary materials, ask them please to be specific. I'll need blood-thinners before this clears up.


THE RIGHT TOOL
I keep both a high quality Turpentine and Odourless Mineral Spirit in my tool-kit. I don't use the turpentine as frequently as the mineral spirit, but there are times when a slow-drying solvent is the best choice.
The Odourless Mineral Solvent that I prefer is really remarkable. Gamsol, by Gamblin. This stuff rocks. If you can find some near to you, try the 2oz bottle. As with much in our hobby, a little goes a very long way!

Peabody out.

6 comments:

  1. A really excellent and informative post, thank you very much. I have often wondered what the difference was - now I know. Fantastic. Thank you again

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  2. You are too kind sir!
    Glad to know I am punting in the right direction. :)

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  3. Welcome back Peabody! Glad to see you posting again. Thanks for the info. Very interesting stuff.

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    1. Thanks! 've been off the grid a bit too much it's true... But I have been hard at work and have a nice back-log of good stuff to post up!

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  4. Cheers for the info, very useful =)

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  5. Really informative thank you! I have just started an upholstery course and the polish I have to make specifically states pure turps (not easy to get and v expensive I have found). I have been true to the recipe and acquired the real thing, but just wanted to know what the difference is. (Still not sure 'why', but this was interesting nonetheless!)

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