From: Christina Z. Anderson (zphoto@montana.net)
Date: 03/08/03-06:51:31 PM Z
Good heavenly days, Judy and list, whoever else cares :)
I found this on the Bostick and Sullivan website in: van Monckhoven,
Désiré van. A Popular Treatise on Photography. Translated By W.H.
Thornthwaite. London, 1863.
Chapter 11:
"here are two excellent varnishes suitable for the purpose--amber varnish,
and the white gum, or Soehnee varnish.
The amber varnish is thus prepared. A quantity of yellow amber, broken into
small pieces, is placed in a bottle so as to occupy about three-fourths of
its capacity. A mixture of equal parts of chloroform and ether is now poured
into the bottle, in such a quantity that the amber is hardly covered. After
some few days the liquid contents of the bottle are poured upon a filter,
and the pale yellow liquid which passes through is amber varnish.
The solid fragments of amber are allowed to remain in the bottle, to which
can be again added the mixture of chloroform and ether, and a fresh quantity
of varnish obtained. The same amber will serve for a dozen or more times,
it' care be taken to keep the bottle well closed.
To prepare the gum-lac, or Soehnee varnish, place in a bottle-
Gum-lac White 2˝ ounces.
Alcohol 35 ounces.
The bottle is now well stopped and left several days, being well agitated at
frequent intervals; the liquid is then left to settle as much as possible,
the clear portion poured off, and the remainder filtered. The whole of the
liquid can be filtered; but it is not recommended, as it passes very slowly
through the paper. The colour of this varnish is of a pale yellow, less deep
than the chloroform.
Instead of making this preparation in a bottle at the ordinary temperature,
it will be found a more expeditious plan to employ a flask (containing the
materials), placed in hot water. If the flask, thus kept heated, be agitated
from time to time, the gum-lac can be dissolved in about halt an hour. There
is always a whitish deposit, which does not dissolve either in cold or hot
alcohol; this must be allowed to perfectly settle before the varnish is
poured off for use.
The amber varnish is very easily applied; the collodion surface of the
plate, on which the picture is formed, is covered with it in the same way as
the collodion was applied, the excess of liquid being received in the
bottle. In a few seconds this varnish is dry. It is well, however, to expose
the plate for an hour to the sun before being used for printing from.
It is more difficult to make use of the white gum-lac varnish, because the
plate then requires to be warmed. For this purpose it is carefully exposed
to the flame of a spirit lamp, or before a clear fire, taking care that the
heat is equally applied by moving about the glass plate at some distance
from the fire, or above the flame, it' this be employed.
The temperature of the glass should be such that, when applied to the back
of the hand, it can be borne without inconvenience. If too hot, the, varnish
flows. with difficulty over the surface; and if too cold, it does not dry
sufficiently quick, and becomes chilled or partially opaque. This varnish is
applied like collodion, the excess being received in the bottle, and when
the surface appears dry, the heat is continued a short time longer, so as to
cause a proper transparency and adhesion of the coating.
It is especially difficult to use the gum-lac varnish for plates of large
size, for which, all things considered, it is generally best to employ the
amber varnish. The negatives are less firmly varnished, and, in consequence,
not able to yield so large a number of proofs; but, on the other hand, it is
much more easily applied."
This archive was generated by hypermail 2.1.5 : 04/22/03-02:37:25 PM Z CST