van Monckhoven, Désiré van. A Popular Treatise on Photography. Translated By W.H. Thornthwaite. London, 1863.

Chapter XI.
Varnishing the Picture

WHEN the proof is fixed, washed, and dried, its surface exhibits by reflected light a fine metallic appearance; if the development has been carried too far, the coating

appears covered with a metallic dust, which, however, can be partially removed with the aid of a very soft brush. By transmitted light the picture has an entirely different appearance, perfectly opposite to that exhibited by reflection.

As a collodion negative is required to furnish a considerable number of positive proofs upon paper, and for which purpose the collodion surface requires to be placed in contact with the sensitive paper, it becomes necessary to protect this coating by a sufficiently hard varnish, so that the plate can be easily handled without risk; other. wise the soft coating would be very liable to injury.

There 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-

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.

It constantly happens that a number of transparent round spots appear on the negative, which require stopping out before the positive proofs are obtained from it, otherwise these white spots would form corresponding black ones on the prints, which cannot be removed. If; on the contrary, the spots on the negative be black o opaque, white spots are formed on the positive proof which are comparatively easy to be touched out by a little water colour.

Fig. 70. Apparatus for touching out Glass Proofs.

Touching out a negative requires very careful manipulation, and a properly arranged apparatus for the purpose will be found very convenient, Fig. 70. The wooden top of a small table is removed, and a thick sheet of glass, supported by an iron framing, is substituted. Below is arranged a large sheet of white paper, stretched upon a frame, or else a looking-glass, of which the inclination can be varied by some such contrivance as shown in the figure.

The light reflected from the looking-glass or paper, enables the proof, which is laid on the glass-plate forming the top of the table, to be conveniently examined by transmitted light.

The transparent spots are then touched out with a very fine camel's hair pencil, and some dark colour mixed with honey or oil.******

Some persons touch out the spots with Indian ink, mixed with a small quantity of Prussian blue, before the plate is varnished. This plan, however, cannot be recommended, as the subsequent varnishing is apt to destroy the colour applied.

Light spots on paper proofs 'are easier to touch out with water colour of the same tint as the print, than glass negatives are; therefore, whenever circumstances allow a choice to be made, preference should be given to the former. For example, if there should be a white spot on the negative, with which nothing can be done, it will be better to make it a black one, which, by printing white on the paper proof, can be then easily tinted of the proper colour.