Hello!
was on my way to a hike when I got your email..
yes, oil of turpentine is well, just turpentine..
HOWEVER hardware or house painters turpentine is usually of TERRIBLE quality.
For fine art painting, and probably for luthiers as well, I always recommend
Windsor and Newton English Distilled which can be purchased at any decent art
store in various quantities and it is really excellent turpentine. It flows
like water, is very pure and very white... Beware of the fumes though... and
avoid getting it on the hands .
While most turpentine related health issues come from extended exposure as
measured in years, it is important to note that some people are allergic to
turps and will fairly quickly develop headaches, dizziness etc on short term
exposures.
I enclose a quick discussion about turpentine as related to our work as luthiers
Natural turpentine is obtained from tapping or scraping the wounds on a variety
of coniferous trees. The crude turpentine (scrape) is about 20% essential oils,
60% solids, and 20% water and waste material.
While the range of products known as turpentine includes balsam oil,
Stroudsbourg and Venetian turpentine; the rosin oils, and oil of turpentine,
have specific but limited applications in the making of varnish. By far the
most important is pure gum spirits. Separating the essential oil and solid
content of crude turpentine makes pure gum spirits. The crude gum is heated,
refined, and separated by distillation into gum spirits and rosin. The
standards for the manufacture of pure gum spirits dates, in the US, to colonial
times when the colonies were a prime source for "naval stores". These same
standards remain in effect today.
In the manufacture of varnish pure gum spirits has a variety of roles. It is a
solvent, a flowing agent, and a drier.
As a solvent in linseed oil varnish, turpentine is unique. Turpentine cannot be
considered a solvent in the same way that alcohol dissolves shellac or water
dissolves salt. These are solutions where a specific quantity of solid combines
with the solvent to form a diluted copy of itself. Evaporate the solvent and
the solid is left unaltered. Linseed oil is highly solvent in turpentine at
room temperature. Once combined however, the turpentine and linseed oil cannot
be separated by distillation into the original components. Turpentine and
linseed oil are mutually soluble. Some resins are directly soluble in
turpentine. Some resins require processing to make them soluble. Natural
varnish resins are compounds. A mixture of turpentine and resin will contain
dissolved and undissolved elements suspended in the mixture. Resin solutions
are colloidal in nature and once established will not break down into their
original components. Natural varnish resins and turpentine are mutually s!
oluble. In the varnish making process turpentine is added to the resin and oil
to promote the mutual solubility of the three elements.
As a flowing agent turpentine is superior to other solvents. If a linseed oil
varnish is made in the same way, except mineral spirits is used instead of
turpentine, and samples of each are brushed on the same surface, the brush
marks will flow out of the turpentine varnish first and most completely. As the
varnish film cures mineral spirits will evaporate completely. Turpentine never
completely evaporates. A small percentage remains in the varnish as an elastic
resinous substance.
Turpentine acts as a drier in linseed oil varnish. When pure turpentine is
exposed to the atmosphere at room temperature it begins to thicken and gain
molecular weight. It absorbs oxygen from the air faster and more efficiently
than linseed oil. In varnish it passes oxygen from the air to the oleo-resinous
compound.
----- Original Message -----
From: Clive Titmuss & Susan Adams
To: lute-builder
Sent: Saturday, March 17, 2007 10:57 AM
Subject: [LUTE-BUILDER] more on mastic inlay
Thanks all for those suggestions. Great to hear from you all and as always
profitable in the saving in time and effort.
The suggestions appear to come down to;
-A ground vegetable pigment to stain the mastic, rather than dye or ink, to
prevent absorption into the softwood grain. Vegetable pigment could be
charcoal, ebony dust coarsely ground (per Stradivari, no less). I also have a
substance referred to as "vegetable black" in a set of earth pigments, which
are clays ground finely.
-Mixing the ground mastic with turpentine by in a bath/filter bag, adding the
pigment when the paste is workable, say with a palette knife, then evaporating
to create the proper consistency. I expect there might be some shrinkage and
that a subsequent fill might be neccessary?
{I have also located a source from a lab supply company in the US for what
appears to be prepared mastic paste, though I could not confirm this with the
supplier, it's still on order. Cost is pretty high, $45 for 25 g. versus about
$17 for the raw tears from Celtic Moon, incense supply. I have a feeling it may
be used for preparing biological specimens such as insects or microscope
slides. Here is the listing and website address:
Mastic Gum, Tears
CAS: 61789-92-2
Consists of Approximately 2% Volatile Oil, Masticinic and Masticonic
Acids, Masticoresene
http://www.sciencelab.com/page/S/PVAR/10420/SLM3196}
-Sealing the rosette rabbett with some untinted resin before filling with
mastic and placing the squares, in this case paua abalone. I have a feeling
this one will be very good advice.
-Making a glue filler with thick hide glue and a (vegetable) pigment or wood
dust. I have done this often in the past, it's very workable and hard, does
not shrink, takes finish and scraping well and is easily prepared.
Only one question: is oil of turpentine the same as turpentine as one would
buy as paint solvent, in other words thin consistency and volatile, or oil
consistency?
[I'm making two Juan Pages six course guitars with all the decor in koa
(quite anachronistic, but beautiful). Very large body, lovely shape, long
string length, a great model.]
Clive Titmuss
[EMAIL PROTECTED]
www.earlymusicstudio.com
early music downloads and cd's
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