U of S | Mailing List Archive | alt-photo-process-l | Re: Miracle size for gum

Re: Miracle size for gum

I agree totally about using step wedges for every testing--I have 3 so I can print 3 at once.
But my Stouffers numbers are blackest black circles (maximum film density) with clear numbers--hence when the printed number is as dark as the area surrounding the step wedge on the print (the gum borders), and the circles are clear paper white, I know I have exposed and developed correctly.  So I am intrigued that your step tablet has middle gray numbers....as my step wedge appears to be the same Stouffers as yours--did they change it recently?
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.