Edwal hypo check and silver concentration per litre.

[Marco Buonocore]

So, like many I suppose, I've been using Edwal's hypo check to keep tabs on my fixer for both film and prints. I keep rough tabs on the amount of rolls or prints I run through the fixer, but invariably lose track along the way.

I rely on it rather blindly, not really knowing what it's 'checking'. My question is this: at what level of silver concentration per litre will the hypo check drops turn milky?

I'm not obsessed with being archival - not enough of my work merits it, yet. But I don't want to be careless. Ilford recommends (in the Hypam data sheet) that for high level permanence, you shouldn't exceed 2grams per litre, and that anything less than 8-10g/l should be fine. Where does the Hypo Check fall in this range?

For what it's worth, both films and paper get fixed in two baths.

Any insight would be most welcome!


Thanks,

 

[Gerald Koch]

I have found that measuring the clearing time for film is a better and more reliable measure of when to replace the fixer. Note the clearing time for fresh fixer. Use a bit of film leader for the test. When this time doubles then it is time to replace the fixer.

For prints you think important, it is best to use a two bath system no matter what measurement criterion you use.

 

[Michel Hardy-Vallée]

Bump for an old thread, I was just about to ask the same question myself by creating a new thread.

All the documentation I've seen so far on such tests only indicate that precipitate=exhausted, but no one ever gives information about how much g/L of silver is needed to trigger the precipitate.

Is it the commercial 2g/L level or the more archival 0.5g/L ?

 

[drpsilver]

18 June 2007

I have also used "Hypo Check" rather blindly, and am also confused as to what silver content constitutes "exhausted". I have begun to use a paper tape that is designed to measure silver concentration (somewhat like how pH paper works). This has allowed me to quantify the amount of silver in solution, but the underlying question is still not answered.

Regards,
Darwin

 

[Snapshot]

I to must admit to using Edwal Hypocheck by rote, rather than understanding the principles behind the hypcheck. Once the precipitate forms, I mix up some new fixer. Any additional information from anyone would be appreciated.

 

[dancqu]

I to must admit to using Edwal Hypocheck by rote,
rather than understanding the principles behind the
hypcheck. Once the precipitate forms, I mix up some
new fixer. Any additional information from anyone
would be appreciated.

That test is of the FT-1 type; FT-1 being a Kodak
designation as are the HT-1 and 2 and the ST-1 tests.
The FT-1 test uses potassium iodide to determine the
reserve capacity of the fixer for silver.

As most know silver chloride, bromide, and iodide are emulsion
ingredients and all are insoluble. Thiosulfate though has a very
strong affinity for silver and does attach with it in the presence
of any of the three ionic halogens I've mentioned. The silver-
thiosulfate complex IS soluble and will wash out. But there
is a limit to how much silver can be complexed.

The amount of iodide added prior to formation of a
precipitate is a measure of the fixer's reserve capacity.
Iodide BTW is a very least soluble silver salt. The FT-1
test is a worst case test for fixer and I still wonder if
it is valid on that basis. Dan

 

[Michel Hardy-Vallée]

But is there any hard numbers about what it means for the precipitate to form? That's the real question.

 

[removed account4]

i don't have a bottle nearby ..
is there a phone number for edwals ?
maybe they can help ...

i know that with sprint fixer, the hypo check isn't
the most reliable measure regarding fixer life ...
not sure if it is true or not, but i was told long ago
that sprint rapid fix can take a "larger capacity" of film/paper ...

 

[dancqu]

Iodide BTW is a very least soluble silver salt. The FT-1
test is a worst case test for fixer and I still wonder if
it is valid on that basis. Dan

That last sentence should read: The FT-2 test ... . Dan

 

[dancqu]

But is there any hard numbers about what it means
for the precipitate to form? That's the real question.

I've never come across any hard numbers. Are you
referring to the one drop test? How exactly do you
perform the test? There are two or three or more
ways of doing so.

One way of tracking a fixers exhaustion as it's
used and ages would be to track the number of
drops needed to produce a precipitate. I've used
10ml samples and counted up to 10 or more drops
when doing tests. Not a certified test method.

For a certified method www.unblinkingeye.com
Click on articles then Archival Processing. Dan

PS: My last most recent post; I was right the
first time, that last sentence ... FT-1 ...