U of S | Mailing List Archive | alt-photo-process-l | Re: Bottem of the Van Dyke Barrel

Re: Bottem of the Van Dyke Barrel

Very complicated question.

Some emulsions do gain speed over time. Some emulsions fog over time. Some just lie still as you would like.

However, assuming the use of fresh materials, the most important issue in emulsion speed and contrast of iron sensitive materials is RH, or relative humidity. Iron based processes may be as much as 2-3 stops faster in RH of 80% or more than in in RH of 30% or less.

If you want o calibrate these processes, stabilize RH.

Sandy King

At 6:57 PM -0600 3/2/07, Michael Koch-Schulte wrote:
At first I thought it was my printer and inks. Then I thought it was a
change in my workflow somewhere. Maybe it was my coating method. No. It may
seem like a silly question but is it just normal that emulsions like VDB,
Cyanotype and others start to gain speed over time? I don't do a lot of VDB
but recently I was testing some of my remaining solution from a batch from
last year and it seems to be printing three or four times faster than it did