From: Tom Ferguson (tomf2468@pipeline.com)
Date: 04/06/02-09:35:44 AM Z
A few thought that might help.
Gum is typically 2 stops faster than plat/pallad, so an hour seem very
excessive. My "typical" exposure is 2.5 minutes under UV tubes.
I think most gum folks are using a saturated Potassium salt solution. How
long are you soaking the print for, some paints take more than ah hour to
clear. Yellow is a tough color, try something more saturated to start
(learn) on, a good deep blue is easier. Most gum folks do the gelatin and
foraldahyde (glyoxal is a newer and nicer alternative) as separate steps.
Hope some of those help.
-- Tom Ferguson http://www.ferguson-photo-design.com> From: Nash Computer Technology <nashcom@btinternet.com> > Subject: Gum - what am I doing wrong? > > Hi > > I managed to get some time at Easter to have a bash at gum printing. I had > made some of the chemicals up at Christmas using the formulae in Scopick's > book. > > I soaked and dried the paper, then brushed on a gelatin/formaldahyde mix and > let that dry. > > I mixed 2g of yellow, red and blue pigments (separately) with 10ml of gum. > > I then mixed 2ml of the yellow pigment solution with 2ml ammonium dichromate, > and coated this on the paper in dim light, and let it dry in the dark. > > I made various test exposures between 1 minute and 1 hour, then soaked the > paper in a number of still water baths. However, there was only the faintest > of images, and the paper didn't clear - the image area stayed a mustard > yellow. > > I had a think about this, then decided to dilute the pigment solutions. I did > a number of tests by adding an increasing amount of gum to 2 drops of pigment, > and brushing onto some prepared paper then soaking in water to see at what > strength the paper cleared. The yellow started to clear to a magnolia colour > at about 2 drops pigment solution to 6 drops additional gum, and going as far > as 20 drops gum didn't seem to make much difference. > > I then had another bash at 1 hour exposure, and got a faint image, but the > paper still didn't clear properly. > > I had been expecting this process to be quite easy (I thought I might be > blessed with some beginner's luck!), and had been planning on making a > tri-colour image. I had a go with making 3 in-camera exposures with > tri-colour red, blue and green filters, and printing with yellow, magenta, > cyan pigments, but I only got a faint image with a muddy brown background. > > By the way, I shot the images on Tri-X rated at 100ISO and developed in Rollo > Pyro for about 4 minutes (about half the time I normally use for platinum). > > Any help would be much appreciated. > > David Nash
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