What Did Cadmium Do?

[Vlad Soare]

I'm just curious. What was the purpose of the cadmium in old papers? What exactly did it do? What can't today's papers do because of their lack of cadmium?
Thanks.

 

[Ian Grant]

The cadmium allowed far greater flexibility with regards to manipulation of image colour/tones of warm tone papers though over exposure and very dilute development.

These papers could be made to yield a wide range of image colours from reds through warmer browns to black purely by development.
The cadmium helped to maintain contrast with the papers, modern warm-tone papers with no Cadmium can't be manipulated by anything like as much.

Ian

 

[Vlad Soare]

I see. I did notice that such manipulations didn't seem to work with current papers, but didn't know it was because of the cadmium. I thought it had to do with emulsion thickness, incorporated developing agents, less silver, or other such things.
Do you happen to know how exactly it worked, I mean what chemical processes involving cadmium were responsible for allowing those manipulations to work?

 

[Cor]

Didn't cadmium also alow longer storage of paper? For sure it allowed better lith printing qualities (ie Kentmere Kentona)

Best,

Cor