by jrburns47 » Sun Feb 20, 2022 9:47 am
Hi Martin,
Thank you for your thoughtful reply. I can see that we’re thinking along similar lines. It’s possibly important to differentiate between the different old glass plate emulsions of Ilford SP696T, Agfa 8E75HD and HRT BB640. The old HRT BB640 results are almost a moot point since I only have about 6 of the old plates remaining for testing. Also please note this conversation only relates to white light transmission holograms. The old HRT BB640 plates are very different visually, after processing, from the old Agfa & Ilford plates, resulting in an almost clear plate with a bright image when properly exposed. The caveat is that, although all my tests have used FeEDTA bleach, the Ilford & Agfa 8E tests used catechol based developers whereas the BB640 used the BB640 ascorbic acid, sodium hydroxide developer. As everyone I think knows, the old BB plates are and were a dramatic improvement over the old Agfa and Ilford plates.
I have also been asking this question about the efficacy of using graded alcohol dry as a final process after a pre-exposure TEA presensitizing and also about isopropyl vs ethanol. I had a good discussion with Dinesh who has had success using isopropyl whereas I’ve always used ethanol. My feeling, based on a long ago run series of tests on the effect of various hardeners on freshly mixed Knox gelatin, was that isopropyl, unlike ethanol & methanol, had the possibility of leading to a crazing or milkiness of gelatin. Dinesh said he had not experienced that in the context of isopropyl graded alcohol drying of silver halide exposures.
I plan to do some testing, i.e., TEA presensitizing & alcohol graded dry. I don’t see why it shouldn’t work.
An additional question is whether a graded alcohol dry helps prevent printout. The anecdotal evidence is possibly. If not, then the desirability of a dilute dichromate bleach anti printout rinse after non-fixed rehalogenating bleaching and washing, as suggested by John Wiltshire, may preclude a graded alcohol drying process. The question there being whether a graded alcohol drying process might negate, or possibly enhance, the anti printout benefit of the dilute dichromate bleach rinse.
In recent discussions with both Dinesh and Mike Medora, I also suggested that it could be the red sensitizing dye in the various old red sensitive emulsions that may have caused the massive loss of apparent sensitivity over decades. I came to the possibility of this conclusion because the similarly old Ilford SP695T and Agfa 8E56HD plates, that I’ve used over the last several years, most recently this last May/June, are much closer to their original sensitivity. I don’t really know if, other than their sensitizers, the old red vs.green Agfa & Ilford glass plate emulsions were the same for their respective brands. Maybe your co-author, John Wiltshire might know.
Other than the massive several orders of magnitude loss of sensitivity, all the different old red sensitive plates are providing good holograms if they receive sufficient exposure and appropriate darkroom processing.
My end objective is to arrive at an optimized visual and archival exposure and processing regime, particularly for the large quantity of old Ilford plates that I have. Although I’ve gotten good results on 4x5” plates, the 12x16” plates will definitely need presensitizing of some sort in order to avoid unrealistically long exposures. Although I’ve gotten good results without obvious defects, the very brightest results all have some sort of issue which almost looks like dissolving gelatin but may be something else entirely such as chemical staining or something about the BIPS layer that Ilford used on these plates or something else entirely. Sometime in the next few weeks I’ll post videos of those odd results.
I’m also planning to try the sodium formate presensitizing suggested by Bill Altschuler based on his experimental holography results giving a 5X increase in sensitivity. His original work for holography was derived from the work of Jacqueline Belloni on photographic emulsions.
If I’m fortunate enough to use up all my existing stock of old materials, I plan to move exclusively to the amazing BB materials
!
I still hate squeegees but am resigned that I probably need to acquire this skill. Peter Miller has promised to visit and give me some hands on squeegee training🥳!
Hi Martin,
Thank you for your thoughtful reply. I can see that we’re thinking along similar lines. It’s possibly important to differentiate between the different old glass plate emulsions of Ilford SP696T, Agfa 8E75HD and HRT BB640. The old HRT BB640 results are almost a moot point since I only have about 6 of the old plates remaining for testing. Also please note this conversation only relates to white light transmission holograms. The old HRT BB640 plates are very different visually, after processing, from the old Agfa & Ilford plates, resulting in an almost clear plate with a bright image when properly exposed. The caveat is that, although all my tests have used FeEDTA bleach, the Ilford & Agfa 8E tests used catechol based developers whereas the BB640 used the BB640 ascorbic acid, sodium hydroxide developer. As everyone I think knows, the old BB plates are and were a dramatic improvement over the old Agfa and Ilford plates.
I have also been asking this question about the efficacy of using graded alcohol dry as a final process after a pre-exposure TEA presensitizing and also about isopropyl vs ethanol. I had a good discussion with Dinesh who has had success using isopropyl whereas I’ve always used ethanol. My feeling, based on a long ago run series of tests on the effect of various hardeners on freshly mixed Knox gelatin, was that isopropyl, unlike ethanol & methanol, had the possibility of leading to a crazing or milkiness of gelatin. Dinesh said he had not experienced that in the context of isopropyl graded alcohol drying of silver halide exposures.
I plan to do some testing, i.e., TEA presensitizing & alcohol graded dry. I don’t see why it shouldn’t work.
An additional question is whether a graded alcohol dry helps prevent printout. The anecdotal evidence is possibly. If not, then the desirability of a dilute dichromate bleach anti printout rinse after non-fixed rehalogenating bleaching and washing, as suggested by John Wiltshire, may preclude a graded alcohol drying process. The question there being whether a graded alcohol drying process might negate, or possibly enhance, the anti printout benefit of the dilute dichromate bleach rinse.
In recent discussions with both Dinesh and Mike Medora, I also suggested that it could be the red sensitizing dye in the various old red sensitive emulsions that may have caused the massive loss of apparent sensitivity over decades. I came to the possibility of this conclusion because the similarly old Ilford SP695T and Agfa 8E56HD plates, that I’ve used over the last several years, most recently this last May/June, are much closer to their original sensitivity. I don’t really know if, other than their sensitizers, the old red vs.green Agfa & Ilford glass plate emulsions were the same for their respective brands. Maybe your co-author, John Wiltshire might know.
Other than the massive several orders of magnitude loss of sensitivity, all the different old red sensitive plates are providing good holograms if they receive sufficient exposure and appropriate darkroom processing.
My end objective is to arrive at an optimized visual and archival exposure and processing regime, particularly for the large quantity of old Ilford plates that I have. Although I’ve gotten good results on 4x5” plates, the 12x16” plates will definitely need presensitizing of some sort in order to avoid unrealistically long exposures. Although I’ve gotten good results without obvious defects, the very brightest results all have some sort of issue which almost looks like dissolving gelatin but may be something else entirely such as chemical staining or something about the BIPS layer that Ilford used on these plates or something else entirely. Sometime in the next few weeks I’ll post videos of those odd results.
I’m also planning to try the sodium formate presensitizing suggested by Bill Altschuler based on his experimental holography results giving a 5X increase in sensitivity. His original work for holography was derived from the work of Jacqueline Belloni on photographic emulsions.
If I’m fortunate enough to use up all my existing stock of old materials, I plan to move exclusively to the amazing BB materials😊!
I still hate squeegees but am resigned that I probably need to acquire this skill. Peter Miller has promised to visit and give me some hands on squeegee training🥳!