Details of exhibit
- Exhibition:
- 1890 [Thirty-fifth] Photographic Society of Great Britain Exhibition
- Exhibit title:
- Photographic Application of "Primuline," a new coal-tar dye
- Exhibitor:
- Green, Cross & Bevan
- Section:
- Apparatus
- Exhibit No.:
- 748
- Description:
- Diazotype Printing
A "positive" process based upon the fact that the diazo derivatives of a newly-discovered group of coal-tar colouring matter - known under the name of Primuline - are extremely sensitive to light, and therefore rapidly decompose on exposure.
The diazo compounds react with a variety of coal-tar derivatives - phenols and amines - to form colouring matters of very rich shades; when decomposed by light this property is entirely lost in the product of decomposition, which is an inert substance.
After exposing a surface sensitive with the diazo compound to the graduated action of light, such as results from the varying tones of a positive, the destruction of the diazo compound is found to have taken place in exact proportion, and the subsequent development produces a coloured picture with an accurate reproduction of the details of the original. In the fully discharged portions (high lights) the colour is the neutral tint of the product of decomposition of the diazo compound. - Exhibit type:
- Photographic equipment and supplies
- Process:
- [Not Listed] ()
- Award:
- medal
