532 
POPULAE SCIENCE EEVIEW. 
The JEJhurneum Process . — During the past three months several other new 
processes have been wrought out and published ; amongst them, that called 
the Eburneum, by which pictures possessing great brilliancy, softness, and 
perfection of detail have been secured. A mixture of gelatine and zinc 
white is prepared — gelatine 5 oz., water 20 oz., glycerine ^ oz., oxide of zinc 
1 oz., — adding the latter to a warm, and not too thick or hot, solution of the 
former, and mixing thoroughly, so as to produce an opaline effect. This is 
then put aside, and allowed to settle, and then carefully decanted into a clean 
bottle ready for use. A clean plate of patent glass is next rapidly coated 
with a saturated solution of the best white bees-wax in methylated ether, 
applied with a tuft of clean cotton wool. When the ether has evaporated, 
or, to use other words, in a few seconds, the plate is rubbed with a piece of 
clean linen kept for this purpose, until a scarcely perceptible coating of wax 
is on the polished surface of the glass. Another solution of 6 grs. of india- 
rubber in 1 oz. of benzole is next used, by dipping therein a camel-hair 
pencil, and passing it round the edges of the glass to the width of about 
one-eighth of an inch. The plate is next coated with some good negative 
collodion, giving a tough horny fibn, and immersed in the usual silver bath. 
On this the positive is printed in the camera, in the way usually adopted for 
obtaining transparent positives. The developing solutions recommended are 
the following — No. 1 for positives from vigorous negatives ; No. 2 for use with 
weaker negatives : — ’ 
No. 1. 
Proto-sulphate of iron 
Citric acid 
Glacial acetic acid 
Water 
No. 2. 
Pyrogallic acid 
Citric acid 
Glacial acetic acid 
Water 
The development is conducted in the usual way, and the image fixed in a 
solution of cyanide of potassium, \ oz. to a pint of water, after which it is 
subjected to a thorough washing for a quarter of an hour, and put up to dry 
in a place free from dust. If the plate is not a small one, slips of paper are 
next pasted round the edges of the glass, so that the edges stand up round 
above the surface, thus forming a kind of dish, into which, when placed on a 
levelling-stand, the gelatine and zinc-white solution is poured. When this 
has set, it is put into a box, having a covering of perforated zinc, in which it 
rests on nails in the sides. Gas or a spirit-lamp is applied, to subject it to a 
heat of about 60° to 70° Fahr., and it becomes hard and dry in about thirty- 
six hours. A coat of plain coUodion or varnish is applied, and when this is 
dry, a penknife passed round the edges releases the whole from the glass 
plate, when the edges are trimmed and the picture complete, — the perfectly 
-smoothed and polished surface given by contact with the glass being one of 
3 to 6 grs. 
3 
20 mms. 
1 oz. 
5 grs. 
5 „ 
10 mms. 
1 oz. 
