RE: Unknown area in Gum printing?
But can help people in making a decision to switch lightsources, dichromate concentration, procedure / environment conditions ect... Maybe there are persons who are not happy with their exposure times - it can be good for them to learn that changing some parameters may help them in that aspect. Anyway, I should admint that was a rather long reply for something that's really not that much important... (Kind of a custom for gum discussions!?) -----Original Message----- From: Katharine Thayer [mailto:kthayer@pacifier.com] Sent: Friday, April 27, 2007 5:13 PM To: alt-photo-process-l@usask.ca Subject: 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. kt 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. > > Regards, > Loris. > > -----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? > > > Michael, > > 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? > > Jacek, > > 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. > > ~m > >
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