ENGRAVING WITH A SUNBEAM. 
151 
and is conducted in tlie following manner : — A press is made in 
the form of a very shallow box, with a hinged lid. In the 
bottom of the box is placed a thick plate of glass, a similar 
glass plate forming the lid. The bottom plate rests on four 
screws, which serve to adjust the plate to any height. On 
this plate is laid, face upwards, the metal intaglio mould, and 
the lid being closed down, the screws in the bottom are so 
adjusted as to bring the upper surface of the mould in equal 
contact with the glass lid. The cover being again raised, a 
small quantity of ink is now poured on the centre of the 
mould, the sheet of paper destined to receive the impression 
is then laid down on the top of the small pool of ink, and the lid 
having again been closed down, the ink is spread out between 
the mould and the paper, filling up the cavities in the former, 
and the superfluous portion escaping over the edges. The 
lid should remain closed for nearly a minute, or until the ink 
sets sufficiently to allow of its being* removed in contact with 
the paper, to the surface of which it is eventually found adher- 
ing. The conditions required in a suitable ink are fluidity 
with rapid setting, transparency, and facility for removal from 
the mould with perfect adherence to the paper. These conditions 
are fulfilled in gelatine, to which any colouring matter may be 
added ; and as the range of transparent pigments is very 
extended, so are the colours in which prints may be produced 
by the process in question. The gelatine is dissolved in the 
same manner as that described in the preparation of the 
mould, and a small quantity of a suitable pigment mixed 
with it. The lampblack of the ordinary capsuled tin colour- 
tubes, with the addition of a little carmine or crimson lake, 
forms an agreeable tint ; but this is entirely dependent upon 
the taste of the operator or the nature of the subject. A 
picture may be printed either in the most sombre black, 
the most intense red, or the richest violet or blue. The 
most suitable thickness of the gelatine ink is best determined 
by experience, and it will generally be found necessary occa- 
sionally to add to it a little water. The ink must be kept warm 
by means of a gas stove or otherwise, the heat and strength 
of the gelatinous ink being such as to ensure its setting in the 
mould in a reasonable time. To prevent the ink from adhering 
to the mould or parting from it readily, the latter must, from 
time to time, be slightly moistened with a sponge or pledget 
of cotton charged with oil. 
When a suitable time has elapsed — usually from half a mi- 
nute to a minute — the lid is raised and the paper removed 
from the mould, taking with it the whole of the coloured 
gelatine, which at this stage forms a picture on the paper in 
relief, and to which peculiarity the name of the process — 
