chlorinated gelatin

[wildbillbugman]

Hello to all,
I ran into this website by accident:www.costaricacoffeeart.com
They sell a chlorinated gelatin that, they claim, can be simply mixed with silver nitrate solution and citric acid to make a working glass negative solution.
However,after braging that it is 50 to 100 times faster than previous such emulsions, they rate the ISO at 0.5.
Is it worth looking at as a "starting point"for gelatin emulsion making,as opposed to starting with photo grade gelatin or phthalinated gelatin?
Regards,
Bill

[Kirk Keyes]

Bill, isn't the guy selling gelatin that has some amount of chloride added? Not much value in that it seems?

[Photo Engineer]

The ISO of any chloride emulsion is going to be very slow. Silver chloride has most of its sensitivity in the UV region and very little in the visible region. In any event, the size of the crystal (and therefore speed) depends on the making procedure, but in this case if the individual is selling active gelatin, it will speed up the emulsion just by the sulfur present. It will also decrease the stability of the emulsion to keeping unless you add some extra ingredients.

PE

[ivanp84]

As biochemist I think that www.costaricacoffeeart.com formula is just simple mixture of gelatin and NaCl. After mixing www.costaricacoffeeart.com gelatin with AgNO3 in darkroom you'll get AgCl colloid in the gel. If you leave on that level you'll never get 100% black, just gray. So you must heat up to 50^C then cool down several times to get proper colloid (in physical chemistry known as Ostwald ripening). The www.costaricacoffeeart.com is very simple formula and I think that I saw in my Serbia a decade ago some high school chemistry projects utilized AgCl + gel + albumin + ...; they printed on unusual materials (rocks, wood, copper, ...)