d be quite desiccated within fifteen minutes.

_The paper is more or less yellow._

1st. The paper tinted with ultramarine.
2d. The sensitizing solution or the developer are not sufficiently acid.
3d. The washing (fixing) in the solution of hydrochloric acid was not
sufficient to eliminate the iron salts from the paper.

_The proofs harsh, devoid of half tones._

1st. The sensitizing solution contains too much iron chlorate.
2d. Exposure too short.

_The paper is stained._

The brush not kept clean while sensitizing.

_Black spots._

They are generally due to metallic dust in the paste of the paper, or from
particles of undissolved salt in the platinite solution.

NB: No good results can be expected unless the paper be kept absolutely
dry before, during and after exposure, when using the former (original)
process.

Impaired sensitiveness of the paper, want of vigor, tinged whites,
muddiness, indicate dampness.

ARTIGUES' PROCESS

The Artigues process, so called, is, without any doubt, the best to be
employed for the reproduction of plans and drawings in lines. It is
simple, expeditious, and yields black impressions on a very pure white
ground which are absolutely permanent. And this is of the utmost
importance when the copies are to be used for military purpose, or kept in
archives, such as those of the Patent Office, for example. Should it not
require the use of negative cliches, it would certainly supersede any of
the processes previously described; moreover, as it will be seen, it can
be employed for many other purposes than that of obtaining duplicates from
original drawings. The objection is not even very great indeed, for the
design can be, without great trouble, transformed into a negative by the
aniline method described in the beginning of this work.

The Artigues process is an adaptation for the purposes in question of the
carbon process invented by Poitevin. We shall describe it in extenso.

The paper can be prepared with any one of the following solutions:

1st. Dissolve 21/2 parts of ammonium bichromate and 5 parts of best gum
arabic in 15 parts of water and neutralize with a few drops of
concentrated aqueous ammonia; then add 100 parts in volume of whites
of egg and a certain quantity of thick India ink, and, this done,
beat the whole to a thick froth. In ten or twelve hours the albumen
will be deposited and ready for use.