A test for paper-clearing time

[M Carter]

If you are referring to the Kodak test solution HT-1a it measures the amount of hypo being released from a print. It is a test of how fast washing is progressing. It really doesn't tell how much hypo or silver remains in the print. At least to me a not very useful test. On the other hand the ST-1 solution accurately shows how much silver remains in a print. Any coloration darker than a barely perceptible cream color shows insufficient fixing. THE TWO TESTS ARE NOT EQUIVALENT. It is possible, depending on how tightly thiosulfate is bound to the paper fibers, for the HT-1a test to give deceptive results.

Older copies of the Kodak Darkroom Guide have a series of swatches that give more accurate values for the amount of residual silver.

Nope, I'm referring to the Formulary's Residual Hypo Test; blot the emulsion side dry, place a small droplet on the border, time it for 2 minutes. Their instructions state that anything beyond a faint cream needs further washing. I consider it about the most important chemical I have.

I understand there are tests for the wash water, but I can't imagine 100ml of that lasting 5 years (but I've never used it). I'm referring to a test that shows how much thiosulfate remains on the print, which seems more meaningful to me.

 

[Gerald C Koch]

Nope, I'm referring to the Formulary's Residual Hypo Test; blot the emulsion side dry, place a small droplet on the border, time it for 2 minutes. Their instructions state that anything beyond a faint cream needs further washing. I consider it about the most important chemical I have.

I understand there are tests for the wash water, but I can't imagine 100ml of that lasting 5 years (but I've never used it). I'm referring to a test that shows how much thiosulfate remains on the print, which seems more meaningful to me.

There are two tests for residual hypo; HT-1a and HT-2. The former one uses potassium permanganate and the latter one uses an acidified solution of silver nitrate. To test for archival permanence you should test for both residual hypo AND residual silver. However most texts on permanence usually recommend ST-1. The HT-2 test is more complicated as timing is important and the test must be conducted in subdued light. For HT-2 a pale cream coloration denotes FAIR while no color indicated GOOD archival permanence. So the test results differ between ST-1 and HT-2.

 

[Anon Ymous]

Another detail about the HT2 test is that it stains everything if left long enough, so judge the stain level at most 3' after application and rinse well afterwards.

 

[Gerald C Koch]

Another detail about the HT2 test is that it stains everything if left long enough, so judge the stain level at most 3' after application and rinse well afterwards.

Yes the solution stains counter tops and clothing. I got a free visit from the dentist because he had spilled silver nitrate on his counter top and wanted to remove the stain. Farmer's reducer to the recue.

 

[M Carter]

There are two tests for residual hypo; HT-1a and HT-2. The former one uses potassium permanganate and the latter one uses an acidified solution of silver nitrate. To test for archival permanence you should test for both residual hypo AND residual silver. However most texts on permanence usually recommend ST-1. The HT-2 test is more complicated as timing is important and the test must be conducted in subdued light. For HT-2 a pale cream coloration denotes FAIR while no color indicated GOOD archival permanence. So the test results differ between ST-1 and HT-2.

I always understood that a drop of straight selenium would show residual silver, and I do that just after fixing and a quick rinse. I assume you'd want to know if it needed more fixing before going through the whole wash process. Not sure what formulation the Formulary product is, it does have silver and will leave gray stains on clothes or surfaces.

These two have worked well for me (testing for fixation and then testing for wash) but I only have prints dating back to the 80's so I can't speak for hundred-year permanence. I don't think I'll add anything more complex than those two.

 

[Gerald C Koch]

I always understood that a drop of straight selenium would show residual silver, and I do that just after fixing and a quick rinse. I assume you'd want to know if it needed more fixing before going through the whole wash process. Not sure what formulation the Formulary product is, it does have silver and will leave gray stains on clothes or surfaces.

These two have worked well for me (testing for fixation and then testing for wash) but I only have prints dating back to the 80's so I can't speak for hundred-year permanence. I don't think I'll add anything more complex than those two.

If you use selenium toner Kodak recommends that it be diluted 1+9. I would assume to avoid false positive stains.

 

[Doremus Scudder]

I see no reason why a drop of sulphide toner would be any less reliable.

Curious now, since I know that Kodak recommends both the ST-1 test and the selenium toner test, but doesn't seem to mention sulfide toner in this regard. Has anyone any information about this?

FWIW, the Formulary residual hypo test seems to be good old Kodak HT-2. Here's the formula with the original Kodak instructions from publication, "Processing Chemicals and Formuals for Black-and-White Photography" J-1, 1971:

"Kodak® Hypo Test Solution HT-2 (Residual Thiosulfate Test)
Distilled Water . . . . . . . . . . . . . . . . . 750 ml
28% Acetic Acid . . . . . . . . . . . . . . .125 ml
Silver Nitrate, Crystals . . . . . . . . . . . . 7.5 g
Distilled Water to Make . . . . . . . . . . .1 l

Store in a screw-cap or glass-stoppered brown bottle, away from strong light. Do not allow the test solution to come in contact with hands, clothing, negatives, prints or undeveloped photographic material; it will stain them lack.

Testing Prints: to determine whether prints are thoroughly washed, wipe the excess water from the face (emulsion side) of an unexposed piece of the same paper being used in the batch of prints being processed, or from the extra margin area of one of the prints. Place 1 drop of the test solution on the face of the processed paper sample. Allow the solution to stand on the sample for 2 minutes, rinse to remove the excess reagent, and compare the stain with the tints shown in the KODAK hypo Estimator, available from photo dealers.

If you want your prints to have good long-term keeping properties, using washing aids such as KODAK Hypo Clearing Agent and KODAK Hypo Eliminator HE-1*. If the above spot test is used after washing aids other than KODAK Hypo Clearing Agent, it may give misleading results. The face may show less stain than a print washed only in water, and yet the hypo content of the two prints may be equal. In cases where, for this reason results obtained with KODAK Hypo Test Solution HT-2 may be unreliable, you may prefer to measure the transmission density of the material after total immersion in the silver nitrate test solution.

Testing the Degree of Washing of Films: After washing, cut off a small strip fro the clear margin of the film ad immerse a portion of it in a small volume of the test solution for about 3 minutes. Well-washed films, including those for record purposes, should show very little or no discoloration.

The spot technique should not be used on wet films because of the danger of spreading the reagent.

A quantitative test for the residual chemicals in films and papers can be found in American National Standard PH4.8-1971, Mehylene Blue Method for Measuring Thiosulfate and Silver Densitometric Method for Measuring Residual Chemicals in Films, Plates, and Papers. ANSI Standards are available from the American National Standard Institute, Inc., 1430 Broadway, New York, New York 10018."

*Note that the use of Hypo Eliminator HE-1 is no longer recommended.
The Kodak hypo estimator strip is no longer available from Kodak. A digital version is available here: http://unblinkingeye.com/Articles/Archival/archival.html

Best,

Doremus

 

[Gerald C Koch]

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".

Which may be why Kodak recommends diluting selenium toners 1+9. Some copies of The Kodak Darkroom Guide have sample swatches to provide a more accurate reading of the test results.

I have no idea why the OP keeps trying to wiggle out of performing the test correctly. ST-1 contains only a single chemical sodium sulfide that should be easily obtainable. Then there is the use of KRST. Really the test is very simple to do.

 

[Rudeofus]

OP lives in Central Europe, and these packaged tests are hard to come by here. Not even Moersch seems to offer them any longer, and shipping Formulary products across the Atlantic is pricey, they seem to have no local distribution channel here either. And to be honest: Formulary Residual Silver Test is way overpriced for what it is: US$ 13 + shipping for 2g of Na2S giving you three months of stock solution shelf life.

I would also be careful with modern selenium toner kits: they appear to be much weaker than their original versions, allegedly due to environmental restrictions. I notice substantially less and slower toning with the Rollei selenium toner that what is typically mentioned in literature about selenium toning. Therefore I would recommend caution before blindly accepting results from a residual silver test done with random off-the-shelf selenium toner.

 

[Gerald C Koch]

The ST-1 test calls for 2 g of sodium sulfite in 100 ml of water. Far more than the average photographer could use. Since the exact amount is not critical buy the 2 grams and visually divide out 0.5 g and store the remaining solid in a tight bottle. Then mix up 25 ml for testing. Et cetera, et cetera, ... This will provide test solution for a full year of testing for a reasonable cost.

Another alternative is to use the Kodak Polysulfide toner T-8 or equivalent which uses liver of sulfur. As before dilute it 1+9.

I do sympathize with photographers in the EU who are thwarted by uncaring bureaucrats in Brussels.

 

[Anon Ymous]

FWIW, I recently bought 500g of sodium sulfide nonahydrate for ~7,5€. I bought that much because it was prepacked reagent, not bulk. This amount makes an awful lot of test solutions and toners and it's much more than what I assume will ever need. That's assuming that these lumps have good keeping properties, is that correct?

 

[Gerald C Koch]

FWIW, I recently bought 500g of sodium sulfide nonahydrate for ~7,5€. I bought that much because it was prepacked reagent, not bulk. This amount makes an awful lot of test solutions and toners and it's much more than what I assume will ever need. That's assuming that these lumps have good keeping properties, is that correct?

The main concern is keeping sodium sulfide dry. I would suggest using canning jars to keep out moisture.

Sodium sulfide can be used as is or converted to sodium polysulfide by dissolving the calculated amount of sulfur in a sodium sulfide solution. This is an exothermic reaction do the addition must be gradual.

 

[Anon Ymous]

The main concern is keeping sodium sulfide dry. I would suggest using canning jars to keep out moisture.

Sodium sulfide can be used as is or converted to sodium sulfide by dissolving the calculated amount of sulfur in a sodium sulfide solution. This is an exothermic reaction do the addition must be gradual.

I assume you meant sodium polysulfide, right?

 

[Gerald C Koch]

I assume you meant sodium polysulfide, right?

Yes, thanks for catching that. I call these mistakes 'cut and paste errors'. You cut and paste and then forget to make the small change necessary.