the 8 hour developmet was to get some differentiation in the two darkest strips of the test wedge, that is fully developed strip. It took so long with this exposure. Whites cleared before that.
I minute is (or was) my standard exposure time for all the layers of the tricolor gum( a bank of UV tubes). This one minute thalo test strip illustrates it very well. You get a full dark and clear whites with about 6 steps on the wedge, negative density of about 0.9. This would illustrate "gum works best with thin negatives" statement that has been around for so long. You can hardly see the letters because they are a middle gray on the step tablet and are washed out (step 4 or 5).
It really takes printing these tests strips to unlearn the gum process and start learning it again on a new level.
Date: Sat, 10 Oct 2009 07:52:52 -0600
Subject: Re: Miracle size for gum
Marek, and Francis,
Thanks for the posting, Marek. I will have to try the stuff as well. My results with acrylic sizing in the past have been iffy at best, but perhaps this is the ticket. I know Peter Blackburn swears by Aquapel, which I also have to try here. So many sizes, so little time....it seems lately when I get time for the darkroom it is time to make work and not do these fun tests which I love to do :(
I just love your posts and tests and visuals--so clear. And your willingness to share your great results.
I am not understanding why it takes 8 hr for water development? Is that to clear the whites or in general?
Your thalo 1 minute exposure has not printed in the numbers on the step wedge tho it appears you have maximum black in your step wedge--is it 1 minute UVBL or some other light source? You are using a 1 minute exposure normally for your bleach development?? You must be using some powerful light there...the reason I ask is yesterday I gave a gum demo to the Printmaking Club and I guessed the exposure for yellow (ha) might be 8 minutes on their behemoth old exposure unit flatbed thingy and I totally baked the layer on. I retried at 3 minutes and even that was long. So I wasted 2 sheets of paper and 11 minutes. I was basing my guess on previous experience with that unit and solarplate which took way longer than expected (no time to calibrate in an afternoon demo--I just winged it, and you know how that goes...)
You are getting great tonal ranges with your bleaching process of choice.
Francis, Venetian Red is a pretty luscious color, isn't it--a sort of bricky lipstick red. It's great with a raw sienna and ultramarine blue. BUT raw siennas sure vary in color, not just in strength, from manufacturer to manufacturer, some being a beautiful yellow and some being a dull ochre. VR is strongly pigmented, too...I used to use it all the time in oil painting.
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