Hardener-added emulsions

[Neanderman]

Elsewhere on this site, a statement was made that incorporating a hardener into an emulsion resulted in a one-stop reduction in effective film speed ((there was a url link here which no longer exists)).

PE, can you comment? Is this true and, if so, can you explain why?

Thanks.

Ed

 

[Photo Engineer]

Hardener does not necessarily decrease speed.

With keeping, as hardening goes on with some hardeners, the emulsion swells less and it loses the ability to develop well and therefore it appears to lose speed. Increasing development time might get the speed back, but the hardener tends to increase fog with time so it is a circular situation which can lead to an effective loss in speed.

I have low levels of hardener in my films and papers. They don't suffer speed losses with hardening or keeping as far as I can determine.

The hardeners that I worked with at Kodak worked so efficiently that they were hard when coated and so no further effect was seen.

In that post, I doubt if hardening caused the speed difference. There would also have been a contrast change.

PE

 

[Neanderman]

hardening goes on with some hardeners, the emulsion swells less and it loses the ability to develop well and therefore it appears to lose speed.

Thank you. That was the direction my thinking was going.

Ed