Re: was Miracle size for gum now tonal range
I don't think I told "I get a longer tonal range". What I told was: "I use / prefer negatives with longer DR", adding now: -to get the tonal range possible with the particular coating solution is able to give. Tonal range (as I understand it) is a function of the pigment and pigment concentration to my knowing.
Ah. I agree that cyanotype and gum are both shorter scale processes, so it makes sense to me to be able to use similar curves/negs.Maybe gum spectral sensitivity is way different than cyanotype, therefore the same negative (color) that reads log 1.4 for cyanotype translates to a lower figure for gum - I can't tell since I haven't checked that with a real (silver) negative.
OK then, you are getting 5 1/3 stops, which corroborates with my stop range for gum, too, and is way different than the supposed 2 stops the one author said. But what I was interested in was the difference between dichromate strength and tonal range...something I will have to do myself on sized paper (have it on unsized, not sized, when I was testing back before I bit the bullet and decided gum printing on sizing was much easier than not sizing).OTOH, I clearly remember posting here a Stouffer 31-step tablet gum (thalo blue) test print showing 16 discernible steps (including dmax and paper white) a couple of years ago.
Well, the way to find the answer to that question is to clear. You are right that the dichromate stain is not in the midtones and highlights, only in darkest darks, so it can give a false read. If you take dichromate alone and expose it (no gum) you can see how it just goes and goes, but essentially if you used that looong exposure for gum you'd bake a print.BTW, I do get some color change in the darkest parts (blacks) of the layer but not too much; it doesn't affect the midtones and highlights. Does that counts as dichromate stain due overexposure? Regards, Loris.
FWIW I never clear, only step wedges when I am trying not to get a false exposure read. But it's funny because at one point in the late 1800's people were panicking because their gum prints faded over time and found out they were relying on the dichromate stain in the shadows to provide some print density when, in fact, over time in sunlight it does bleach to a pale sage green.