primuline

When the material to print upon is thick and wholly impregnated with diazotized primuline, it is advisable, since the insulation could not be prolonged to effect the change through, to expose the back of the material for a certain but short period in order to _clear_ it.

Photographic Reproduction Processes Peter C. Duchochois

The sensitiveness of diazotized primuline to light, when united to organic substances and the different colors which can be obtained with the unaltered compound, have given rise to an interesting printing method, the invention of Messrs.A. G.

Photographic Reproduction Processes Peter C. Duchochois

By itself diazotized primuline is slowly influenced by light, but quickly acted on in presence of organic substances.

Photographic Reproduction Processes Peter C. Duchochois

All this, except the impregnation with primuline, should be done in the dark room.

Photographic Reproduction Processes Peter C. Duchochois

It is pretty certain, however, that nitrogen is set free, for if gelatine imbued with primuline be immersed in water after insulation, nitrogen is set free and can be collected as usual in a tub filled with water and inverted on the substance.

Photographic Reproduction Processes Peter C. Duchochois

Here we must state that the primuline process seems to be better adapted for the reproductions of drawings, such as made for the black process, and of opaque photo-clichés in lines, or white and black, than for printing in half tone.

Photographic Reproduction Processes Peter C. Duchochois

If the material so dyed be placed in an acidified solution of nitrous oxide, the primuline is diazotized, forming a derivative compound of a deeper color, which fades in the light, and which in presence of amines and phenols gives rise to a variety of dyes whose color depends on the reagent employed, while, when acted on by light, the resulting compound is entirely deprived of this property.

Photographic Reproduction Processes Peter C. Duchochois

Paper is impregnated with primuline either by floating or brushing.

Photographic Reproduction Processes Peter C. Duchochois

In other words, the diazotized primuline acts as a mordant only when not altered by the luminous action.

Photographic Reproduction Processes Peter C. Duchochois

The chemical change light effects in the diazotized primuline is not well known.

Photographic Reproduction Processes Peter C. Duchochois