RichardThat's good, but keep in mind, just as the book suggests, I'm interested in this formula as a substitute for HT-1 not HT-2. My goal is to have a better hypo test for film without going to methylene-blue.
Regards Ralph W. Lambrecht http://www.darkroomagic.comThis electronic message contains information that is confidential, legally privileged or otherwise protected from disclosure. This information is intended for the use of the addressee only. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, printing or any other use of, or any action in reliance on, the contents of this electronic message is strictly prohibited. If you have received this communication in error, please notify the sender and destroy the original message immediately.
P don't print this e-mail unless you really have to On Nov 22, 2009, at 23:09, Richard Knoppow wrote:
----- Original Message ----- From: "Ralph W. Lambrecht" <info@xxxxxxxxxxxxxxxx >To: <pure-silver@xxxxxxxxxxxxx> Sent: Sunday, November 22, 2009 1:33 PM Subject: [pure-silver] Mystery Hypo TestRichard mentioned this book a few times: 'Photographic Facts and Formulas'. I was lucky enough to get a copy of the 1975 edition on Amazon for a song. Good book! On page 156, it lists a nameless formula of a hypo test for film, apparently far more sensitive than Kodak's HT-1a, which is listed on the previous page. mercuric chloride 25 g potassium bromide 25 g water to make 1000 mlThe book goes on to explain that it was suggested by Crabtree and Ross(big names) and gives a detailed description of its application.Has anybody ever used this? Why does it not have a name? Is it a best-kept secret because of its first ingredient? Regards Ralph W. Lambrecht http://www.darkroomagic.comThe standard test for hypo is the methylene blue test. This is more sensitive than the silver nitrate test and can be quantitative. I don't remember where the details are at the moment but think they are in an ISO standard. I think I know about the test above but don't remember much about it. Anything with a mercury compound in it is worth avoiding. Not only is mercuric chloride hard to obtain it is an extremely toxic substance. I think this test is a pretty old one. The silver nitrate test can also be made quantitative by fixing the stain in a sodium chloride solution and measuring the density in comparison to stains on similar material made with known amounts of hypo. Again, I can't remember where the procedure is detailed. Possibly in Grant Haist's book but my copy is stored away. I will do some research on this, youv'e got my curiousity piqued.-- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = ====================================================================== To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.