I think the Ilford fixer is a non-hardening fixer. Not sure,
Kodak made non-hardening rapid fixer with the hardener and an
acid supplement as a separate solution. The acid tends to
decompose the thiosulfate. Fixers usually have either sodium
sulfite or some substitute in them to protect the thiosulfate.
The sulfite also serves to prevent the reaction products of
carried over developer from causing stains. A mixture of
thiosufate and sulfite makees a satisfactory fixing bath. A
certain amount of acid added will prevent carried over developer
from continuing to develop. A running water rinse after
developing will wash out most of the developer. Of course, an
acid stop bath will stop development almost instantly and deliver
the material to the fixing bath in an acid condition.
Many fixing baths are buffered to maintain a fairly constant
pH. Although the acid in a fixing bath will keep carried over
developer inactive its main purpose was to activate the hardener.
If no hardening action is needed the hardener can be left out and
just enough acid included to stop the developer.
Thiosufate is not dependent on pH to work. A fixing bath can
be acid or alkaline or neutral. An alkaline bath really has no
advantage. While emulsions wash out faster when in alkaline
condition an after bath will achieve this regardless of the pH of
the fixing bath.
A plain fixing bath is composed of about 240 grams of
crystalline thiosulfate/liter and about 5 grams of sulfite per
liter for a non acid fixer and about 15grams of sulfite for a
normal acid, hardening bath. The extra sulfite will not hurt the
non-acid bath.
The standard fixing bath is Kodak F-5 and a variation of this
was published as an odor free fixer. Getting rid of the acid also
gets rid of the odor, which is sulfur dioxide, a very irritating
gas.
All this applies equally to both sodium thiosulfite and
ammonium thiosulfite (rapid fixer).
BTW, in some old books, mid 1930s vintage, will be a chart
showing the speed of fixing vs: the concentration of thiosulfate.
It was in error but the error was not discovered for some years.
The curves show a peak in the fixing speed at a concentration of
around 240 grams/ liter, an amount found in many fixing baths. It
turns out that the condition of the emulsion has a strong effect
on fixing speed. When the emulsion is dry when it goes in the
fixing bath the curve shows the peak; when the emulsion is wet,
i.e. saturated, thee is no peak and the rapidity of fixing
continues to increase with fixer concentration to quite high
levels. However, the established formulae were not changed
although some later ones do make use of higher concentrations of
fixer.
Oh, golly, I didn't mean to write that much.
On 8/8/2021 2:14 PM, John Stockdale wrote:
About the fixer: I think that if there's no powdery precipitate then it would be ok. Acidic fixers tend to self-destruct causing elemental sulphur to come out as precipitate. The Ilford fixer is acidic but maybe not very acidic.
best regards, John
=========================================
On 9/08/2021 4:58 am, mark@xxxxxxxxxxxxxxxxxx wrote:
.......============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
Also the fixer is an ammonium thiosulfate formula, and Ilford put a batch number on one of the bottles, but I see no expiration date. Don't know if one can tell if it can be used confidently from that. Will call Ilford tomorrow and see what they say.
Thanks for the help
