U of S | Mailing List Archive | alt-photo-process-l | Re: Unknown area in Gum printing?

Re: Unknown area in Gum printing?

It seems rather pointless to compare exposures, when they depend on so many variables, such as type of light, dichromate concentration, and ambient humidity, for starters. My exposures with the photoflood typically run 2-3 minutes for a very hard layer, but comparing exposure times is comparing apples and jellybeans.

On Apr 27, 2007, at 7:01 AM, Loris Medici wrote:

My typical gum exposures are 4 minutes when using *plain paper*
negatives (w/o oiling)! (Sensitizer is 25% AD though...) The resulting
layer is not weak and can withstand spray development.


-----Original Message-----
From: Don Bryant [mailto:dsbryant@bellsouth.net]
Sent: Saturday, April 21, 2007 3:44 PM
To: alt-photo-process-l@usask.ca
Subject: RE: Unknown area in Gum printing?


You should know better, attachments shouldn't be sent to the list! :)

14 minute exposures! Wow that's seems like a long time and I thought my
UV printer was slow.

Don Bryant

From: Michael Koch-Schulte [mailto:mkochsch@shaw.ca]
Sent: Thursday, April 26, 2007 5:03 PM
To: alt-photo-process-l@sask.usask.ca
Cc: gonsaj@iinet.net.au
Subject: Re: Unknown area in Gum printing?


Where's the Stouffer stepwedge you shot with these test prints? You do
own a Stouffer wedge r-i-i-i-ight? ^) Until you shoot that you have no
idea if you're getting the correct dMax in the print. I routinely shoot
my gums at 14 minutes for many, but not all colours. The time used is
based on how they test with the wedge. Also, if you're calibrating your
negatives using an imagesetter you might want to consider making a stock
pigment/gum mix at this point and then adding equal amounts of potassium
dichromate, gum and water to that.