Hardening fixer formula
After a vacation break I plan to get back to work on my emulsions and I was browsing Denise's page (which is an awsome help to any gelatin newbie :)) and I found Kevin Klein's emulsion formula which seemed to me pretty nice and worth of trying (especially that the examples of pictures used in the article are more or less what I'm aiming to).
After reading, giving it some thoughts and doing some research I have not managed to find any hardening fixer formulae (which is used in Kevin's recipe). I suppose it is some kind of a mix of Hypo fixer and chrome alume...
Normally I would buy one but it's very hard to get here and brewing some for myself seems more "appropriate" to gelatin emulsion ;).
Anywho, if any of you guys have any formula to share (and maybe some tips how to use it properly), it would be awesome.
Thanks and cheers!
Use Kodak's F-5 formula. I believe that it is a hardening fix. There is also one in Anchell and Troop IIRC. If you cannot find one with these references, let us know. I'm sure I can find them.
F-5 Hardening Fixer
Water at 125F (52C) - 2500ml
Sodium Thiosulfate - 960g
Sodium Sulfite - 60g
Acetic Acid, 28% - 190ml
Boric Acid - 30g
Potassium Alum - 60g
Cold water to make 4000ml
This is according to Natural Color Processes by Carlton Dunn
It is posted here in the articles section on fixers!
Thanks guys, I'll try it as soon as i'll get back from the vacation.
I haven't used F5, but it is said that it smells quite a bit (sulfur dioxide). F6 is almost odourless and it's formula can be found, among others, in Kodak's technical publication J1 (page 38).
F6 does not harden as well as F5 or F7 due to the higher pH. The Alum is less effective as pH goes up.
Which formulation does Kodak sell as Rapid Fixer?
Rapid Fixer with Hardener is close to F-5 using Ammonium Hypo and being adjusted to a pH of about 4.5 or 5.
Nice to hear from you again. I hope you're having a great vacation. I certainly approve of your vacation reading material :D.
When I started making dry plate negatives, I just carried over the basic processing techniques I'd used for years with commercial film negatives -- most recently Heico fix with half the recommended hardening additive. Works fine, but if you are interested in pursuing as historical a path as possible, you might follow the advice of T. Thorne Baker in Successful Negative Making, 1905. Baker wrote it as a short manual for using the newly available commercial gelatin dry plates. He writes,
"The quantity of hypo used in the fixing bath varies according to the make of the plate used, but in general a solution of:
Hypo ..... 5 oz
Water .. 20 oz
will be found to answer well. Some makes of plates contain a larger percentage of silver iodide than others, and these require a very strong bath, such as eight ounces of hypo to the pint of water." p33.
And on p35, "In hot weather it is sometimes necessary to employ a hardening bath, in order to prevent frilling at the edges of the film. Alum, chrome alum, or formalin are the recognized agents for hardening, and they are of power increasing in the order named. Thus a five percent solution of alum may be used, a one per cent solution of chrome alum, or a very weak solution of formalin. Blistering is most frequently caused by transferring a plate from a warmish developer to a freshly-made and therefore very cold fixing bath; it is essential to avoid sudden temperature changes when dealing with gelatin."
I don't know if you have any trouble getting chrome alum, but plain (potassium) alum should be readily available as a home canning supply. It's no longer recommended as such because of health concerns, but a lot of home preservers still use it and it's very inexpensive -- at least in my area.
Looking forward to seeing more gorgeous plates!