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Solvents The volatile essential
From Gum Turps to plain water solvents have many uses as you make paint
both in the process of paint making and for cleaning up equipment
afterwards. They are dealt with here in 4 main groups of which 2, water
and turpentine are by far the most important.
Related Links:
Pigments
Binders
Paint characteristics
Warning Use with care
With the exception of water, solvents are flammable substances and
particularly so in the form of confined vapors. Always use solvents
with adequate ventilation, and be careful to avoid open sources of
ignition. The risk increases as the strength of the solvent increases,
but even solvents thought of as being safe to handle such as Grain
Alcohol should be used and stored in a way mindful of possible harmful
effects.
Also with the exception of water all solvents are toxic to at least
some degree including the inhaling of vapors. Any artist who has
experienced headaches after painting with oil paint in an enclosed
studio is experiencing the toxic effects of Turpentine vapors. This is
not recommended, and good ventilation is required when using these
substances.
Water Cleaner as well as
paint ingredient
Water is the only solvent that is used for making all forms of paint,
although it is less likely to be used as a direct ingredient in oil
paint, so much as as a cleaner.
As a paint
ingredient.
Distilled water is the only form that water is ever added to paint
mixtures. Ordinary tap water may contain impurities that can chemically
react with, or discolor some pigments. Untreated water is also likely
to contain microscopic life which can spoil paints, especially when
stored for long periods. In the Renaissance artist's dealt with this in
2 ways. Firstly they collected pure water directly in earthen
containers as it rained (and not off a roof) and also paint when not
used in a very short time was discarded as not being fresh enough. Now
that we use tubes spoilage like this becomes an issue. Egg tempera
needs particular care in this regard as it is a food product and
particularly prone to spoilage, so always use distilled water only.
As a cleaner.
Clean tap water is fine for cleaning equipment. Aqueous paints dried
on equipment are best softened in hot water first and alcohol will
usually dissolve aqueous mediums. Acrylic is always soluble in
alcohol, and so long as your clothes are not an acrylic fiber, alcohol
can always be used to remove water based paint from most surfaces
including clothes With clothes it is wise to test first in case the
dyes in the fabric are also alcohol soluble or otherwise affected
by the alcohol.
Clean oil based paint from equipment while still wet as oil based
paints once dry are insoluble except in the strongest solvents. Use
turpentine to dissolve the bulk of the paint, and then wash the residue
of in warm soapy water, and then rinse in pure clean water. Metal tools
need to be dried carefully so as to prevent corrosion.
Wetting agents Helping
solvents work
Some pigments resist getting wet. This is particularly true of organic
pigments. Alcohol and Turpentine are solvents that are already
excellent wetting agents for oil based paints but water based paints
need a hand at
times too from an outside substance. Ox Gall is the traditional product
for
this and is readily available in any store that sells watercolor
supplies. A product of the acrylic manufacturers is proving to be even
more effective. It is sold under the name Surface Tension Breaker by
Matisse.
Alcohol Aka Methylated
Spirits or Grain Alcohol
For most purposes denatured alcohol, often called Methylated Spirit is
suitable. In places where the denaturing includes noticeable dyes this
is less desirable. Pure grain alcohol is available where the common
denatured product is objectionable. 94% grain alcohol contains water
but
is fine in most cases. Absolutely water free alcohol is called
anhydrous. Many jurisdictions require permits to use these non
denatured alcohol's. Rubbing alcohol should never be used as it
contains
up to 25% water and various denaturants that are unsuitable for paint
use.
Denaturants commonly found in Methylated Spirit include Methanol and
Pyridine both of which are included to make the mixture less palatable
for drinking. Methanol is more poisonous than grain alcohol but is
actually a better solvent and can be substituted for grain alcohol
where the denatured product is objectionable if suitable precautions
are observed for handling this more toxic substance. Methanol is also
called Wood Alcohol.
Alcohol can be used as a wetting agent for certain pigments such as
those organic pigments that resist wetting easily when grinding. This
alcohol should subsequently evaporate during the grinding process and
not cause long term problems. Denaturants such as Methanol will
likewise evaporate without problem, but some other denaturants
including dyes may be more long lasting.
Turpentine The universal
solvents for oil paints
Turpentine and Mineral Spirits have been known since Greek and Roman
times but were made in small quantities for use in medications only.
They were not adapted for use in paints until the Renaissance when
large scale production methods were devised. It has been pointed out
that the use of oil paint as an artist's medium began due to the
introduction of volatile solvents as before then the paint was too
difficult to handle and so was unpopular because of this.
Gum Turpentine
The smell of Gum Turps permeates the oil painter's studio and is
attractive in a way that no other studio smell is. To hear painters
talk of the smell of Gum Turps you would think they were addicted to
it. Unfortunately in many cases that is literally true, at least mildly
so, just as it is for those who regularly sniff other volatile
substances such as glue.
Gum Turpentine despite its attractive odor is toxic and should
never be used without adequate ventilation and should never be used in
open pots or jars. The practice of keeping dirty brushes soaking in
open jars of Turpentine should be avoided. Despite the toxicity, Gum
Turpentine is one of the least flammable of the volatile solvents.
Turpentine is distilled from the sap of various Pine trees. In old
writings the word turpentine refers to oleo resinous substances that we
now call Venice or Strasbourg turpentine. These turpentine's still
contain the resinous element. It was only in the 19th century that the
Gum Turpentine that we are familiar with was born when manufacturers
started to distill the volatile portion from the resin (which is called
rosin).
Gum Turps should always be fresh stock as it deteriorates with exposure
to both air and light. There is no quality difference between the
expensive product sold in small bottles for artist's and the far
cheaper industrial supplies as they both come from the same source.
However the industrial product is likely to be far fresher as it is
sold in greater quantities. Some of the larger hardware stores
sell pure Gum Turpentine, and if you can access this supply it is an
excellent choice, although be wary that it is not reduced with wood
Turpentine which you can tell by smell.
Gum Turpentine is the only thinner and solvent that the artist can use
for damar, as it does not dissolve well in Mineral Turpentine.
Mineral Turpentine
As a general solvent it is an excellent choice as it has few of the
drawbacks of Gum Turpentine. It is cheaper and it does not deteriorate
with time. It is also less toxic and is easier for those with allergies
to use. Despite these advantages most artist's won't use it because
either they don't like the smell or are not aware that it is just as
good as Gum Turpentine as a solvent.
Its general properties are similar to Gum Turpentine with the exception
that is cannot be used to dissolve damar or be used to thin paints that
have a resin content.
Odorless Turpentine
Various substances are sold under this name from Mineral Turpentine to
various Turpentine's distilled from various trees. Citrus Turpentine is
one that is common these days. I am unaware of any investigations of
any of these other than Mineral Turpentine by respected artist's
materials authorities, although the manufacturers claim they are not
problematic. Mineral Turpentine is fine to use but I am wary of the
other products for the time being until independent testing is done
that is relevant to artist's usage. As Mineral Turpentine is the least
allergenic of these solvents and is known not to harm the paint film it
should be the first choice for those who are allergic to Gum
Turpentine, or wish to avoid Gum Turps toxicity. For those who are
still affected by any solvent I would recommend investigating the many
good features of Egg Tempera or other water based media.
Historic solvents.
Oil Of Spike
Lavender.
This is quite different to Oil Of Lavender which comes from a different
plant, Oil of Spike comes from the Lavendula
spica which grows wild in Europe. Until the 19th century (when
today's Gum Turpentine originated) it was the most common solvent used
by oil painters. It is therefore found in many early recipes. It has
the drawback that it retards the drying speed of the oil and it
deteriorates quickly in air. Gum Turpentine or Mineral Turpentine are
both superior products and should replace Spike Oil. It has been
suggested that the only reason that it was more popular in early
centuries was because as a common wild plant it was easy to make.
Venice Turpentine
and Strasbourg Turpentine.
These oleoresins are used less as solvents than as resinous additives
to paints. They have the benefit of imparting greater flexibility to
oil films. They are considered relatively non yellowing and durable
Strasbourg Turpentine was regarded in past centuries as superior but it
is harder to find and is expensive. Venice Turpentine is conversely
easy to get and cheaper. Neither is used in industry anymore and
artist's are the only users of these Turpentine's. They have a good
reputation in Egg Tempera when a egg-resin type of Tempera is desired.
Mixed with stand oil Venice Turpentine makes an excellent varnish.
Go to Historic Pigments page
Stronger solvents 'Thinners'
For most making of artist's paints these stronger and therefore more
toxic and dangerous solvents are never necessary and should not be
used. They come with exotic names such as Xylol, Toluol, Benzol and
N-Hexane. Automobile paints are usually thinned with substances such as
these and are sold as 'thinners' for spray painting. Avoid their use
unless you are experimenting with epoxy resins or other paints that
require stronger thinners. They are more toxic than traditional
solvents and very flammable. Experiments with these sorts of paints
should not be conducted in the average studio but in appropriately
equipped workshops and garages.
Go
to Safety page
References
Alberti, L B, On Painting 1435
(Penguin Classics)
Cellini, B, The Life Of Benvenuto
Cellini, finished 1562 but not published until 1730
(Heron)
Cennini, C d'A, The Craftsman's
Handbook. 1437 (Dover)
Doerner, M, The Materials Of The Artist And Their Use
In Painting, 1921 (Harcourt Brace)
Eastlake, Sir C L, Materials For A History Of Oil
Painting, 1847 (Dover)
Feller, R L, Artists Pigments 1986
(National Gallery Of Art / Cambridge University)
Gettens, R J, and Stout, G L, Painting
Materials: A Short Encyclopedia, 1942
(Dover)
Gottsegen, M D, A Manual Of Painting Materials And
Techniques, 1987 (Harper & Row)
Maire, F, Colors: What They Are And What To Expect Of
Them, 1910 (Drake)
Mayer, R, The Artists Handbook Of Materials And
Techniques, fifth edition 1991 (Faber
& Faber)
Merrifield, Mrs. M P, Medieval And Renaissance Treatises
On
The Arts Of Painting 1849 (Dover)
Muther, R, The History Of Painting From The Fourth
Century To The Early Nineteenth Century, 1907 (Putnam)
Parkhurst, D B, The Painter In Oil 1898
(Lothrop, Lee & Shepard)
Patton, T C, Pigment Handbook, 1973
(Wiley)
Porter, N Webster's Revised Unabridged
Dictionary, 1913 (Merriam)
Pliny, The Elder (Gaius Plinius), Natural
History, 77 AD (Penguin Classics)
Roy, A Artist's Pigments: A Handbook Of
Their History And Characteristics, 1994
(Oxford University Press)
Taubs, F, A Guide To Traditional And Modern Painting
Methods, 1963 (Thames & Hudson)
Theophilus, On Divers Arts, 1125 (Dover)
Various, Encyclopedia Britannica,
fifteenth edition 1981 (Encyclopedia Britannica, Inc)
Various, Paint And Painting, 1982,
(Winsor & Newton / The Tate Gallery)
Various, The Artist's Colormen's
Story, 1984 (Winsor & Newton)
Vasari, G, The Lives Of The Most Excellent Painters,
Sculptors And Architects, 1568 (Penguin Classics)
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