Miscellanies. 335 
9. Method of permanently fixing, Engraving, and Printing from 
Dag uerréotype Pictures: by Dr. Brrres, of Vienna. 
- The method of permanently fixing the Daguerréotype picture with 
a transparent metal coating, consists in the following process :— 
I take the pictures produced in the usual manner, by the Daguerré- 
otype process, hold them for some minutes over a moderately-warmed 
nitric acid vapor, or steam, and then lay them in nitrie acid of 13° to 
14° Reaumur, in which a considerable quantity of copper or silver, 
or both together, has been previously dissolved. Shortly after being 
placed therein, a precipitate of metal is formed, and can now be 
changed to what degree of intensity I desire. I then take the helio- 
graphic picture coated with metal, place it in water, clean it, dry it, 
polish it with chalk or magnesia, and a dry cloth or soft leather, 
After this process, the coating will become clean, clear, and transpa- 
rent,* so that the picture can again be easily seen. The greatest care 
and attention are required in preparing the Daguerréotype impres- 
sions intended to be printed from. The picture must be carefully 
freed from iodine, and prepared upon a plate of the most chemically 
pure silver. : 
That the production of this picture should be certain of succeed- 
ing, according to the experiments of M. Kratochwila, it is necessary 
to unite a silver with a copper plate; while upon other occasions, 
without being able to explain the reason, deep etchings or impres- 
sions are produced, without the assistance of the copper plate, upon 
pure silver plate. 
The plate will now, upon the spot where the acid ought not to have 
dropped, be varnished ;| then held for one or two minutes over a 
weak warm-vapor or steam, of 25° to 30° (Reaumur) of nitric acid, 
and then a solution of gum arabic, of the consistence of honey, must 
be poured over it, and it must be placed in a horizontal position, with 
the impression uppermost, for some minutes. Then place the plate, 
by means of a kind of double pincette, (whose ends are protected by 
a coating of asphalt or hard wood,) in nitric acid, at 12° or 13° (Reau- 
mur.) Let the coating of gum slowly melt off or disappear, and 
commence now to add, though carefully and gradually, and at a dis- 
a solution of nitric acid, of from 25° to 30°, 
for the purpose of deepening or increasing the etching power of the 
solution. After the acid has arrived at 16° to 17° (Reaumur,) and 
gives off a peculiarly biting vapor, which powerfully affects the sense 
of smelling, the metal becomes softened, and then generally the pro- 
ae EE Dt 
however thin, can be trans- 
tance from the picture, 
* We do not well see how a film of metallic silver, 
parent. 
i This and some other passages, are a little obscure. 
