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Mysteries Of The Vortex (Part One)
Mysteries Of The Vortex (Part One)
Author: Martin Reed (Silverprint)
Published by Les McLean
19th November 2008
Default Page 5


Other considerations

Water hardness:

An area that is seldom considered in relation to washing is the relationship between the degree of water softness, or hardness and washing time. Many salts – some of which are contained in hard tap water act as hypo clearing agents. Their carbonate and bi-carbonate ions operate in an ion exchange reaction that speeds the washing process. Pure water such as distilled water, the “softest” possible water is surprisingly relatively poor at washing. This effect was investigated by Kodak in tests at its plants in Harrow and Manchester UK on washing motion picture film, which has a hardened emulsion less easily washed than conventional camera film. In reaching a good commercial thiosulphate level, tap water washed 20 times more quickly than deionised water. Moreover, the harder Harrow water washed at 5 times the rate of the softer Manchester water. Remember that this large variation will be much smaller when washing papers processed without hardeners. The effect of water hardness on wash quality is so geographically specific that it is impossible to make recommendations other than to test your washing with HT-2.


Contaminants in tap water
:

There are many reasons besides saving water for avoiding long wet times for FB prints. Excessive wet times may leach brighteners, weaken the structure of the paper, affect dimensional consistency, or cause the emulsion to lift off the paper or chip at the edges. But there is another good reason to avoid long wet times.

Ralph Steiner, in an unpublished treatise on print washing, observes that during extremely long washes his prints actually picked up contaminants from his water supply. His washes lasting two hours produced cleaner prints than test washes he performed lasting 12 hours or more. This factor is also too closely tied to local water supplies to generalise about, but avoiding potential contamination from unknown substances in your water is another good reason to increase the efficiency of the wash and to minimise both the length of the wash and the amount of water used.



Paper base weight:


Most fibre papers are what is termed double weight (240 grams per square metre). Single weight (140 g/m2) papers are still available from a few manufactures. There are also several heavier weight papers, including Kodak Elite and Forte Museum, which use a 300 g/m2 base. From my own tests it appears that the base washes faster than the emulsion, and consequently, no allowance need be made for heavier base papers. There are no published recommendations for increased washing time to allow for 300g density, but if in doubt, a 10% increase over the wash time used for 240g/m2 papers would seem an adequate precaution. This is another reason for testing the wash quality of your own preferred papers with HT-2.


Hardeners
:

The use of hardening fixers in paper processing is recommended by Ansel Adams in his classic text The Print, and this has encouraged their enthusiastic use. However, there is no point in using a hardening agent in the fixer unless it’s for a particular purpose, such as preventing the print from sticking to the blanket of a glazer during heat drying, or when processing at high temperatures. The bottleneck in washing is the rate of thiosulphate diffusion from the emulsion side; this is further aggravated by the presence of a thin, hardened gelatine super-coating. Using a hardening agent tends to “trap” thiosulphate within the emulsion layer by compacting the emulsion, making it more difficult to wash efficiently, and preventing washing to an optimum level. If you use a hardener, it is virtually mandatory that you also use a wash aid. Doubling the wash time when employing hardeners is the rule of thumb, but an HT-2 test really is required.


Effect of low temperatures on washing time:

Low wash temperature wash results in compacted emulsion, which washes more slowly. Ilford suggests a straightforward doubling of washing time when the temperature is below 10C. A temperature lower than 3 – 4C is rarely encountered in water coming through ground pipes. The use of hypo clearing agent mitigates considerably the problems caused by using cold water.


Fixer silver level
:

Under-fixed prints can be washed well and have most of the fixer removed, but they still won’t be stable, tending to “print out” on exposure to light, producing staining. Another cause of instability in fully washed prints is that the fixer silver level may have been too high, and thiosulphate and fixation by-products may be bonded on to the silver structure of the paper. These won’t wash out with any amount of washing, and are likely to be revealed by a yellowing in the print highlights when exposed to light for any length of time. Rather than test the paper for retained silver, the simplest measure is a preventative one; monitor the capacity of the fixing bath(s), or use silver estimating paper to check the build up of silver in the fixing bath(s). A colour change on the estimating paper is compared with a reference chart that gives the silver level. A level of 2 grams per litre is recommended by Ilford whether fixing in single or twin baths for “commercial” work, but the practical minimum is 0.5 g/litre when working to archival standards. This equals roughly 40 8 x 10 prints per litre for commercial, 10 8 x 10 prints per litre for archival work. Two bath fixing is recommended for archival work; this allows the first bath to be loaded up to 2g/litre, while the second bath is maintained at the 0.5g/litre or below.


Desirable level of residual thiosulphate
:

In the early 80’s it was established that a certain (small) level of thiosulphate retained in the emulsion and base actually stabilised the image, by preventing or reducing image oxidation. This is extremely convenient, and means there is no longer any reason to agonise over the remaining 0.01 grams per square metre of thiosulphate remaining after an archival wash (it is also another reason why hypo eliminator is not needed). However, the discussion has quieted since then. Fuji has been the main proponent of the beneficial effects of the trace level, but their work has been mainly on microfilms. Recent work by Ilford on RC papers failed to show a similar stabilising effect. A standard for the recommended retained thiosulphate level should arrive eventually, but a significant amount of work is still required. Ilford’s opinion is that a level of around 0.015 – 0.02 g/m2 (0.15 – 0.2 ug/cm2) is likely to be adopted. A rider to the issue is that this thiosulphate level is beneficial only when the image is to be displayed. If the print is for archival use – meaning that it will be stored predominantly in darkness – the lowest possible level of thiosulphate is preferred.

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  #1  
By Mike O'Pray on 20th November 2008, 12:40 AM
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Many thanks for this Les. Now it's set out and easily accessible.

Mike
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  #2  
By Argentum on 20th November 2008, 10:44 AM
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Thanks for that Les, I've snaffled it and converted into pdf for local reference.
Now if part 2 was only in text format instead of scanned magazine pages I could do the same but with a much smaller file size.
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  #3  
By Ag-Bromide on 21st November 2008, 08:57 PM
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I hope Martin Reed makes it available as a PDF for downloading (unless I`ve missed it on Silverprint`s site).
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  #4  
By Argentum on 21st November 2008, 09:13 PM
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Part 2 is available from the web site but its scanned pages from a magazine which makes it 16MB.

http://www.silverprint.co.uk/pdf.asp

mysteries of the vortex part 2
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  #5  
By Dave miller on 21st November 2008, 09:41 PM
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We will be posting part two here shortly.
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  #6  
By Andrew Bartram on 26th November 2008, 08:56 PM
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What a fantastic resourse this User Group is! I have long mourned the demise of "Darkroom User" Magazine and regularly re-read the original "Silverprint Manual" that went on to be the original AG+ Periodical (now sadly too much devoted to digi stuff I don't want to think about).
Some of the above was indeed published in the Silverprint manual.
Thanks Les for making it available
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  #7  
By Martin Aislabie on 9th December 2008, 01:46 PM
Thumbs up FB Washing Explained

What a well argued piece of work, with some back-up data to support his case.

So often these articles are a mixture of old wives tales and opinioneering.

Thanks for posting it Les

The only thing that puzzles me - why Martin doesn't have this article on his web site along side Part2 ?

Martin
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  #8  
By Les McLean on 9th December 2008, 03:19 PM
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Quote:
Originally Posted by Martin Aislabie View Post
What a well argued piece of work, with some back-up data to support his case.

So often these articles are a mixture of old wives tales and opinioneering.

Thanks for posting it Les

The only thing that puzzles me - why Martin doesn't have this article on his web site along side Part2 ?

Martin
When I spoke to Martin to ask his permission to use the article he asked me to let him have the scans I made from the original publication for he had lost his copy of the first part.
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  #9  
By Dave miller on 9th December 2008, 05:32 PM
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Quote:
Originally Posted by Les McLean View Post
When I spoke to Martin to ask his permission to use the article he asked me to let him have the scans I made from the original publication for he had lost his copy of the first part.
He could just post a link to this site.
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