[Alt-photo] HT-2 residual hypo test

`Richard Knoppow dickburk at ix.netcom.com
Sun Aug 6 16:17:28 UTC 2017

    The methylene blue test is not necessary for ordinary pictorial 
work. Note that the recommendations for residual thiosulfate changed 
around the mid-1960s due to the discovery that very small amounts of 
thiosulfate in the emulsion acted to protect the image silver from 
attack by peroxides. The earlier requirements were for essentially zero 
thiosulfate but this was found to actually accelerate image degradation. 
The currently recommended thiosulfate levels can be obtained by normal 
processing using two bath fixing and a sulfite bath treatment. Much 
better image protection is obtainable by toning in any sulfiding toner 
or in selenium toner provided toning is carried out far enough. There is 
great detail about this in the literature.
    I have no idea of how this applies to alternative printing processes 
such as salt printing.

On 8/6/2017 7:22 AM, Siegfried Rempel via Alt-photo-process-list wrote:
> ANSI uses methylene blue in an involved procedure for silver processed film
> (microfilm in particular).
> On Sun, Aug 6, 2017 at 2:27 AM, Jacques Kevers via Alt-photo-process-list <
> alt-photo-process-list at lists.altphotolist.org> wrote:
>> Marek,
>> On Philip Greenspun's LUSENET forum, in the B&W Photo - Printing &
>> Finishing section, you can find this:
>> [....]Deep in the instructions for the Kodak Hypo Estimator it says "This
>> test procedure does not conform to the ANSI method of determining residual
>> thiosulfate levels".[....]
>> Likewise, on the Photographers' Formulary Residual Hypo Test it says "While
>> the test is adequate for everyday printing, it is not sensitive enough to
>> be used for archival printing".[....]
>> http://greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=001UL5
>> So I'm wondering whether this is the ideal way if you are looking for
>> something more scientific...
>> No idea on what would be more adequate, though...
>> Best,
>> Jacques
>> Jacques Kevers
>> Beau Site
>> Première Avenue 7
>> B-1330 Rixensart
>> Belgium
>> +32 2 653 56 02
>> 2017-08-05 19:06 GMT+02:00 Marek Matusz via Alt-photo-process-list <
>> alt-photo-process-list at lists.altphotolist.org>:
>>> All,
>>> I am looking for a test chart that Kodak used to sell with the HT-2
>>> residual hypo test that quantifies the amount of thiosulfate in the
>> paper.
>>> This was used in the B&W days to test for washing of the prints. I am
>>> trying to be more scientific about my salted paper printing.
>>> Does anybody have such a chart and could scan it for me.
>>> Marek
>>> _______________________________________________
>>> Alt-photo-process-list | altphotolist.org
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Richard Knoppow
dickburk at ix.netcom.com

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