U of S | Mailing List Archive | alt-photo-process-l | Re: Gum Humidity Question

Re: Gum Humidity Question

P.S. I will say, however, just as a general anecdotal observation, that I haven't seen noticeable differences in contrast between prints I've made at 100% humidity (in the air, not in the gum coating) and those I've made at 60%.

On Sep 26, 2006, at 2:31 PM, ericawd wrote:

According to Christina Z. Anderson and Kosar:

7. Humidity: The presence of a certain amount of moisture in a coated and
dried layer is necessary for the hardening reaction. When dry, the moisture
remaining varies with relative humidity. Completely dehydrated or fully
swollen coatings do not show any light sensitivity at all, but in between
the sensitivity is high when the humidity is high. Sensitivity doubles with
increase of 30% humidity.

In my experience, I have found the above to be true. My question is, in the experience of the gum printers, what effect might humidity have on contrast? Lower humidity equals higher contrast or vice versa? All other things being as equal as they can be with gum.

Candace Spearman