DE103516C - - Google Patents

Description

IMPERIAL

PATENT OFFICE.

PATENT LETTERING

CLASS 57: Photography.

According to R. Ed. Liesegang (Photo (Korrespondenz 1898, p. 561) has a cone solution of ammonium persulphate under certain as yet unspecified circumstances on the a silver image embedded in gelatine in such a way that initially it is completely bleached of the image takes place, whereupon the originally black areas can be seen by immersing it in lukewarm water can dissolve.

So a relief is created from a negative in which the unexposed areas are highest lie while the exposed ones are more or less eaten away.

However, as Liesegang states, the creation of a relief does not always succeed by name not with panels, which makes working with this method very unsafe.

It has now been found through experiments that a weakly acidified hydrogen peroxide solution Gelatin silver pictures also transferred into gelatin reliefs. In contrast to the effect of the ammonium persulphate is however the effect of the hydrogen peroxide solution is entirely reliable; the enigmatic Failure, which Liesegang mentions in his procedure, occurs in the present one not a; this fact is decisive for the technical usability of the process.

When the peroxide of hydrogen acts on the silver image produced in gelatin the most covered parts are attacked first, and in such a way that they are attacked by the Surface of the layer of a gradual peeling of the silver together with the gelatin, in which the silver particles are embedded occurs. With prolonged exposure will also the midtones and finally also the thinnest parts of the image are removed.

This behavior of the hydrogen peroxide can weaken the lights too harshly Developed silver bromide gelatin negatives can be used. Of far greater scope it appears, however, that the gelatin silver pictures treated with hydrogen peroxide show a well-developed relief even after drying, which is suitable for the purpose the light press printing process can be used.

To carry out the process, mix z. B. 100 ecm three percent hydrogen peroxide solution with 2 ecm of pure hydrochloric acid from the spec. Wt 1.19.

Put the gelatin silver picture in question (negative or positive) into this solution and move the bowl in the usual way. The first action takes place after 5 to 10 minutes noticeable as the most covered parts begin to peel off. After 10 to For 20 minutes the procession has already been prepared so far that all the silver collects the same thing enveloping gelatin is dissolved out. The treatment of an im Warnerke sensitometer exposed the plate and then developed it quite hard and clearly, by considering the gradual progression of the action from the most subdued to can follow the thinnest parts of the picture very well.

Claims (1)

If there are larger areas in the picture with so much coverage that the silver precipitate reaches down to the surface of the picture carrier, it is advisable to pass the layer through Bathing in a 5 proc. Alum solution before the Hardening treatment with hydrogen peroxide. Pa ten τ-An s ρ ruch: , Process for the preparation of gelatine relief form, consisting in the fact that a weakly acidified hydrogen peroxide solution is used to act on silver images (negatives or positives) produced in gelatine.