Some toning regimes will be effective at revealing the same problems as the residual silver test reveals. So the toning (or bleach and redevelop toning) steps serve as a check on your fixing regime. If it stains when you tone, you need to fix more completely.Some authors recommend the paper strip to be either sulphide toned or developed after fxinig and washing. What's the purpose of these additional steps?
the idea is that all residual silver(silver that wasn't removed by the fixer)will tone or develop and show a lack of fixing;if no toning or developing takes place,fixing was complete and perfect.Some authors recommend the paper strip to be either sulphide toned or developed after fxinig and washing. What's the purpose of these additional steps?
Thanks, that makes sense. I wonder why this test is not more widely promoted, no need for the ST-1.
Why not, clearing time should be enough, adding 100% or so more is a safety factor.For a couple of reasons:
First, finding the clearing time for a particular paper does not automatically give you the fixing time.
Why... too little, too much?SNIP: so I would be hesitant to use the "2x-rule".
Possibly but not necessary true. But then again, ST-1 reveals no more, does it?Rendering halides in the paper emulsion undevelopable by fixing them is not the same as making them soluble and able to be easily washed out. There could be (probably are) lots of silver compounds left in the paper emulsion or, in the case of fiber-base paper, in the paper base, that won't react to developer, but are not yet at the point that they can be washed out. If you just double the clearing time, you may not be giving enough time for the fixer to do its job.
Our eyes are not a good indicator for archival fixation, and the clip clearing test establishes exactly one thing: time it takes fixer to remove enough silver halide such that the clip becomes mostly transparent. In the course of extended experiments researchers determined across a wide range of established film products, that fixing for twice the visually established clearing time typically leads to archival results.Why not, clearing time should be enough, adding 100% or so more is a safety factor.
there is a formula to make it yourself.No, I would like to know why some tone or develop after fixing for clearing time. These test solutions are not available outside the USA.
Dorms is correct but the 2x rule works reasonably well.Overfixing is not the answer residual silver complexes are hard to wash out of paper fibers.For a couple of reasons:
First, finding the clearing time for a particular paper does not automatically give you the fixing time. People argue over film fixing time (should it be 2x or 3x clearing time?). So, once you have a clearing time, how do you know how much longer to fix the paper so that it is adequately fixed? Paper formulations are different than film, so I would be hesitant to use the "2x-rule".
Rendering halides in the paper emulsion undevelopable by fixing them is not the same as making them soluble and able to be easily washed out. There could be (probably are) lots of silver compounds left in the paper emulsion or, in the case of fiber-base paper, in the paper base, that won't react to developer, but are not yet at the point that they can be washed out. If you just double the clearing time, you may not be giving enough time for the fixer to do its job.
Papers, especially fiber-base papers need a lot fresher fixer to fix them adequately than film. For film, dissolved silver in the fix can go to 10g/liter without serious effect. For papers, even for non-archival "commercial grade" processing, dissolved silver needs to be kept under 2g/l. For optimum permanence, dissolved silver in the fixer should be somewhere in the 0.2-0.5g/liter range. One use of finding the clearing time for film is for knowing when to discard the fix. The standard rule is to discard the fix when the clearing time approaches 2x that in fresh fix. For paper, with its need for much less exhausted fixer, finding a factor of the clearing time to indicate when to toss the fix is just not a precise enough way to determine fixer exhaustion. The "2x-rule" for film just doesn't apply here.
If you can't get chemicals to test, then follow the manufacturers' capacity recommendations and use two-bath fixing for papers.
As for testing: First, if you are unable to test, please trust the manufacturers who have and follow their recommendations. This will give you better results with less trouble than fiddling around with paper-clearing times. Ilford has good info here: http://www.ilfordphoto.com/Webfiles/2006130218312091.pdf
If you can get selenium toner, you can test for residual silver at least. Kodak gives instructions for using their KRST as a test reagent. Place a drop of selenium toner mixed 1+9 on a blank white area of a fixed and well-washed print. Let stand for 2-3 minutes and then rinse off. Any stain other than a very light yellowing indicates residual silver. This test works in lieu of ST-1. I just use KRST concentrate undiluted for this test.
HT-2 chemicals are a bit trickier to source, but by using a wash-aid and using wash-time recommendations plus a bit of a safety factor, you should be able to be confident that your print washing is adequate.
Hope this helps,
Doremus
a lot of this is avoided by two-bath fixing in film-strength fixer, HCA and a 30-minute washThe problem with using paper developer for testing complete fixation is that some paper developers produce dyes themselves, usually from humic acids formed by oxidized developer. These dyes can yield misleading results.
If you want to use sepia toner for testing fixation, there are two types:
The biggest advantage of getting ST-1 is the established color chart, which tells you precisely how to interpret the result. It is trivial to make a full and extremely cheap substitute for ST-1 yourself (check darkroom cookbook for formula), so there is no reason to buy it twice IMHO.
- so called odorless toners, which are Thiourea plus an alkali. Thiourea is a fixer by itself and may alter the result of a fixer test.
- the smelly toners, typically consisting of Sodium Sulfide, and guess what? That's exactly what you get if you buy ST-1 or similar.
Note, that a fixer tester alone doesn't tell the whole story. Even a perfectly fixed print will deteriorate if washing is incomplete. And that's where it gets really messy: better fixing means shorter required wash time, and less than perfect fixation can be covered up to some extent by prolonged washing.
Reason is simple: mostly complete fixation will leave poorly soluble mixed alkali silver thiosulfate compounds in the emulsion, which take much, much longer to wash out. Sadly, this runs contrary to typical dark room sessions, which start with fresh fixer and hours of wash times, and end with exhausted fixer and no time for prolonged wash cycles. Fortunately there are residual hypo testers for checking archival washing.
I would like to point out, that most selenium toners are also loaded with Thiosulfate. Unless you have good reference samples, I would not blindly follow the results of an uncalibrated test with randomly chosen "fixer test solutions".I have some Agfa Viradon NEW left, might use this instead of a developer.
I would like to point out, that most selenium toners are also loaded with Thiosulfate. Unless you have good reference samples, I would not blindly follow the results of an uncalibrated test with randomly chosen "fixer test solutions".
Hi Doremus, Why not, clearing time should be enough, adding 100% or so more is a safety factor.
Why... too little, too much? ... Possibly but not necessary true. But then again, ST-1 reveals no more, does it? ....
Our eyes are not a good indicator for archival fixation, and the clip clearing test establishes exactly one thing: time it takes fixer to remove enough silver halide such that the clip becomes mostly transparent. In the course of extended experiments researchers determined across a wide range of established film products, that fixing for twice the visually established clearing time typically leads to archival results.
This purely heuristic result has worked well so far, and anyone challenging this many decades old rule of thumb better provide some verifiable fixer test results to back up their claims.
I would like to point out, that most selenium toners are also loaded with Thiosulfate. Unless you have good reference samples, I would not blindly follow the results of an uncalibrated test with randomly chosen "fixer test solutions".
Kodak suggests using Rapid Selenium Toner diluted 1+9 as a substitute for ST-1. The test is performed as described by Kodak. Mix up a small amount and keep it in a dropper bottle. The solution should keep for about six months.
Unless I'm wrong, it's pretty simple... Leave some trimmable border on the print, even 1/8";
If you use selenium toning to test proper fixing, and your highlights and borders turn yellow, your print is screwed.
- After fixing and a quick rinse, squeegie the print, blot the border dry with a paper towel, and apply a TINY droplet of straight selenium toner to the border; if it yellows or turns brown, your fixer is shot or your time was too short.
- After final wash, squeegie, blot, and use Residual hypo test on the same border area - just takes a tiny droplet
If my methodology is off, let me know?
I agree that testing for adequate washing is important too. If sourcing the chemicals is difficult though, making sure you fix well with fresh fix and not exceeding capacity and washing for the recommended time plus a bit for safety should do the job. That's what I'd do when in doubt. I test though.
I'd guess in most developed areas, ST is available. The residual hypo test may be more limited, but I understand it's a simple formula that uses (maybe?) some silver compound.
My issues with the hypo test is it's about $25 for a 100ml bottle - which would last me about a decade; but they say it's good for 24 months. I have trouble throwing away expensive chemistry - mine is 3 years old, I've used maybe 20% of it if that, and it still seems to work. Maybe I need to check with PE about the "real" life of it, and if regrigeration or antyhing would prolong it.
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