U of S | Mailing List Archive | alt-photo-process-l | Re: How many gum layers (Re: ferri sesquichlorati)

Re: How many gum layers (Re: ferri sesquichlorati)

On Oct 25, 2006, at 9:27 AM, Keith Gerling wrote:

" Otherwise, why not just start with an image, invert it and make a negative of any unknown density without a curve and keep fiddling with it until you get what you want in the print."

Best Wishes,
Mark Nelson

Well, Mark, that is exactly my approach and it does seem to work. However, having been challenged by recent workshop participants as to why NOT use a curve of some kind I admit that I have been fiddling around with curves lately and have found that the curve that works best for me is a straight line, i.e., no curve at all. So I'm curious. Are there list members out there that DO use curves for gum printing? Might one of them be persuaded to share their curve with me so that I can try it? I'll figure out some way to repay a kind soul for this generosity.
Keith, I'm not sure it would be helpful for someone to "share their curve" since it's my understanding that a curve is specific to a specific emulsion and printing conditions. So the curve I've been developing is only for Prussian blue (and probably M. Graham Prussian blue at that) at a specific gum/pigment ratio, mixed 1:1 with saturated ammonium dichromate, and printed on Arches bright white sized with gelatin and glyoxal, under an EBV photoflood for 2 minutes, at a temperature of 60 degrees F and 75% RH, from an inkjet negative printed on the specific kind of cheap transparency I'm using (whatever it is). Any deviation in that protocol would necessitate drawing up a new curve, because the curve is intended to fit the protocol exactly.