I can't offer any opinions on the use of Sandorac resin as an emulsion
component for gum printing since I am not a "gum crank" stevea@cse.unsw.edu.au (yet).
However, here is what Herbert Wolfe said in his book _Printing and
Litho Inks_ [4th ed. New York: MacNair-Dorland, 1949]:
SANDARAC. This resin resembles mastic very closely and comes
on the market in the form of tears. It is the dried exudation of the
tree "Tetraclinis" indigenous to the Near East. It is used for the
manufacture of hard white spirit varnishes for labels, cardboard, wood
and metals. It is more soluble than mastic.
for Mastic Wolfe writes:
This is a resinous exudation from the "Pistacia lentiscus," a
tree cultivated in the Grecian Archipelago. Incisions are made in the
trunk and large branches, from which the sap on exuding either hardens
on the bark in tears, or drops to the ground, where it is caught in
cloths. It is of light yellow color and is nearly oderless. It is
often employed in the manufacture of high grade varnishes of pale
color for the protection of oil paintings. It is soluble in both
alcohol and turpentine.
Wolfe also notes:
All natural resins, with the exception of shellac, are formed
by the solidification of the resinous sap of trees, and are
classified, according to their age, into recent and fossil types. The
recent resins are obtained either by the accidental wounding of living
trees, or by the deliberate tapping to collect the sap. The fresh sap
contains both resins and volatile oils. The latter are removed either
by distillation or evaporation. The hardness and solubility in oils
and solvents of the recent resins depends, in large measure, on the
percentage of volatile oils remaining after treatment.
Just for fun here are two formula using sandarc from a paper titled
"History of Varnish Making" by T. Hedley Barry [VARNISH MAKING.
London: Oil & Colour Chemists', 1939]:
White hard spirit varnish.
5 galls. sandarac,
2 galls. spirit, 60 o.p.
Warm till dissolved, then add
1 quart turpentine.
Brown hard spirit varnish.
3 lbs. sandarac,
2 lbs. shellac,
2 galls. spirit.
-greg
>===for PGP Key finger Greg Schmitz <gws1@cunix.cc.columbia.edu>===
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Key ID: A7026B1D Key Size: 1024 bits Created: 1994/11/10
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