Changes in ambient humidity and temperature have little effect on the sensitivity of the UltraStable pigment films. Furthermore, Dark Reaction, the spontaneous hardening of dichromate sensitized films, is practically non-existant with gelatin layers sensitized with Azido compounds. Another problem with dichromate sensitization, post-exposure variations in densities if not processed immediately, is also a non-problem with the UltraStable films.
Originally Posted by gmikol
Off topic a bit.
Originally Posted by gmikol
Well, I just learned that the hard way. Recently used three tissues I made a few months ago. Had good notes from my initial prints. Used the exact same negatives, sensitizer & exposure times. Now wanting to make the most of my limited time, I exposed & mated all three.
Upon development - No tone/paper white until around what should have been zone 7. OOPS
But I fixed the blister problem
No problem with the use of potassium dichromate to sensitize the Carbon Tissue BUT
I make myself my Carbon Tissue for use in 8 days
I always use fresh potassium dichromate
I do not include potassium dichromate in the formula of carbon tissuer
I cupped awareness but still the same concentration, the same temperature, the same time awareness, the same drying time, the same humidity
I use always the same formula of Carbon Tissuel in eight days of its manufacture
I always use the same kind of digital negative with Software appoints an application that I created for Carbonl
My exposure time is always the same, I confirm
This just to say my personal experience but I'm just practicing as a small amateur photography Carbon
Thank you, Charles!!
Originally Posted by CMB
That's a huge change in sensitivity. I always thought that the influence of humidity/moisture was maybe +/- 1 stop. Not the huge change you saw.
Originally Posted by R Shaffer
At the risk of going further off-topic, it makes me wonder whether something else changed between then and now. Sensitizer measurement error, bulb aging, etc.
PS--Rob, if you want to discuss this further, we could probably have the mods split this off into a separate thread.
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Greg's post in the diazo thread just made me think of this.
Could I substitute dichromate for permanganate in the clearing bath A?
I know, the irony is terrible... but I don't have any permanganate on hand and wouldn't mind clearing the print I have.
I just thought that the powerful oxidizing nature would do the same thing as permanganate, just like in reversal processing.
Don't know about dichromate, but I just tried hydrogen peroxide. Some web reading suggested that it's oxidizing ability was enhanced in acid solutions. I only had 3% stuff around (drug-store H2O2), so here's what I tried:
Originally Posted by holmburgers
100mL 3% H2O2
~1mL 40% citric acid solution (this is about 0.4g).
It created a just-noticeable lightening of the dye stain in an all-white area (drop test) after about 90 seconds contact. Perhaps if you can easily get your hands on 10% or stronger H2O2, it might be a viable option, and one that eliminates the need for potassium permanganate.
Thanks Greg, I might have to give this a shot. I do love grocery store photo chemistry!