Hello to PE and All,
I have compleated my last evaluation of my current batch of panchro emulsion until I have recovered from my upcoming surgery sufficiently to move around and lift things.
My last experiment was to add O.5 M% of formalin to the the emulsion. As I have observed befor, by adding formalin to my type of emulsion, based on silane functional PVA instead of gelatin, the formalin produced two benifits. First, it caused the emulsion to coat more smoothly. The craters I observe without it are greatly reduced. Secondly, fogging is greatly reduced. I have observed the latter time after time with the type of of emulsions I am making. I do not pretend to know the reasons why. But it works. I would bet my left little toe on it. Glyoxal is more tricky. I avoid it since I once crosslinked one of my emulsions immediately upon adding the glyoxal.
When I get back to wet work, there are 2 more things that I need to do befor I begin using this emulsion to produce in camera color seps.-A, I must reduce the alcohol precipitations from 2 to 1. My emulsion,after re-uptake in water, was too thin. So I did a second alcohol precipitation being more careful to press out and drain as much water as I possibly could. The second re-uptake required a higher temperature, giving rise to more foging. 2- I would like to replace SDE 3008 with a cheaper sensitizer. There are many green sensitizers that cost far less than $600/gram+convenience fee.
In late May-June, I will return to this work and eventualy post the formula and procedure here.
Bill
Formalin usually causes an increase in fog. It is a reducing agent. Formalin may be reducing defects due to some surfactant property or just by dilution and lowering viscosity. Or it may slightly increase viscosity at the edges of defects and pull them together through a change in surface tension.
Yes PE,
The Formalin vs. fog thing is a mystery. Maybe the surface tension change you mentiond might somehow inhibit foging. I just DK.
I test my emulsions for fog by developing in D19. This developer is an agressive, high contrast developer and will usualy produce more fog than other developers.
BILL
And haven't even read this, but it looks interesting... The Action of Optical Sensitizers on the Photographic Plate, G. Kornfeld. Kodak Research Laboratories, Rochester, New York. Received May 25, 1938. http://www.nap.edu/openbook.php?record_id=9565&page=97
I want to ask everyone a basic question , Why anybody does not use original Kodak,Ilford,Fuji or others technology to sensitize their emulsions ? I saw PE had posted a list also .
I think someone could buy a good amount of sensitizer which had been produced for EFKE, Foma.
I dont think EFKE invest Kodak money to the chemicals in Croatia , they might have a local source !
There are thousands of patents waits to be analyzed in Europe and US also.
That is handwaving but I start to research from poorer manufacturers , Russian and East Europe and China.
Chris , invest your time in www.alibaba.com. China is very cheap to find chemicals.
When you reference "original...technology", what era of emulsion making are you thinking of? In the beginning, there was no sensitization. That was followed by red food coloring, and then a fast-moving wave of chemicals that came and went -- with slight variations among Kodak, Ilford, and Agfa. (Fuji: I don't know much about.) Anyway, I don't think procuring sensitizing chemistry that would have been familiar to emulsion makers in the 1920s is much of a problem. I'm using a number of them.
d
Denise Ross www.thelightfarm.com
Dedicated to the Craft of Handmade Silver Gelatin Paper, Dry Plates, and Film
Denise, would you be interested in a spectrosensitometer? Bill? That is... if I theoretically had one to offer?
I really do think that such an instrument could be cobbled together with a little bit of effort. This might be a project that I'd be able to work on in the relatively near future (winter). I'm thinking about something made out of foam-core to begin with, but a prototype could lead to something made of wood.
It might not be perfect, but I think it might be more useful and easier to interpret than shots of color charts.
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