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#31
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Andrew McCall wrote in message ...
Hi Folks, The college I go to have recently decided not to use a stop bath when developing film as the gasses it produces seems to agitate some students with asthma. ... I will probably be developing my film at home now, but I was wondering if I have to, will developing at college with no stop bath have an effect on my negatives. Use water as a stop bath instead. While it doesn't neutralize the alkaline developer the way an acid stop does, the sudden sharp dilution of the developer has much the same effect. Or use a citric acid stop bath, instead of acetic acid. Acetic acid smells (vinegar). Citric acid doesn't. Laura Halliday VE7LDH "Que les nuages soient notre Grid: CN89mg pied a terre..." ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte |
#32
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Uranium Committee wrote: Tom Phillips wrote in message ... Uranium Committee wrote: The problem as I see it is that when the stop bath hits the film in a tank it may do so unevenly, causing some streaking. I did occasionally experience this. You must have been naked and hallucinating in your darkroom... By flushing the developer out with water under a little pressure or flow, one is assured of a kinder, gentler end to development. I simply leave the tank full of developer, and begin pouring water in through a funnel into the neck of the Paterson tank. This way, the water replaces the devloper, and the developer is not left clinging to the film in uneven layers, which can happen when the tank is emptied and allowed to drain before the next step. This developer clinging to the film can cause uneven development. Troll nonsense. Developer simply continues to develop until exhausted. Doesn't cause "uneven" development, since the negative density controls the effect. Uneven coating of developer will certainly cause streaking, as would occur when stop bath is splashed onto the film that still has areas that are wet with developer. One does not "splash." One immerses. Also, with either a water rinse or an actual stop bath diffusion should occur at the same rate. Being acidic, stop bath works quicker by neutralizing developer _alkalinity_ and thus has the advantage of preventing carry over. I rinse the film thoroughly with lots of water that displaces and replaces the developer over about 7 seconds. The point is that the change-over is more uniform, because the water does not arrest development instantly, but smoothly. Sorry. Diffusion takes at least 30 seconds and the developer continues to be active in thin (less dense) areas of the negative. Development in the emulsion is not arrested ("smoothly" or any other way) by dilution, but simply continues to develop until exhausted. |
#33
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Uranium Committee wrote: Tom Phillips wrote in message ... Uranium Committee wrote: The problem as I see it is that when the stop bath hits the film in a tank it may do so unevenly, causing some streaking. I did occasionally experience this. You must have been naked and hallucinating in your darkroom... By flushing the developer out with water under a little pressure or flow, one is assured of a kinder, gentler end to development. I simply leave the tank full of developer, and begin pouring water in through a funnel into the neck of the Paterson tank. This way, the water replaces the devloper, and the developer is not left clinging to the film in uneven layers, which can happen when the tank is emptied and allowed to drain before the next step. This developer clinging to the film can cause uneven development. Troll nonsense. Developer simply continues to develop until exhausted. Doesn't cause "uneven" development, since the negative density controls the effect. Uneven coating of developer will certainly cause streaking, as would occur when stop bath is splashed onto the film that still has areas that are wet with developer. One does not "splash." One immerses. Also, with either a water rinse or an actual stop bath diffusion should occur at the same rate. Being acidic, stop bath works quicker by neutralizing developer _alkalinity_ and thus has the advantage of preventing carry over. I rinse the film thoroughly with lots of water that displaces and replaces the developer over about 7 seconds. The point is that the change-over is more uniform, because the water does not arrest development instantly, but smoothly. Sorry. Diffusion takes at least 30 seconds and the developer continues to be active in thin (less dense) areas of the negative. Development in the emulsion is not arrested ("smoothly" or any other way) by dilution, but simply continues to develop until exhausted. |
#34
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Tom Phillips wrote in message ...
Uranium Committee wrote: Tom Phillips wrote in message ... Uranium Committee wrote: The problem as I see it is that when the stop bath hits the film in a tank it may do so unevenly, causing some streaking. I did occasionally experience this. You must have been naked and hallucinating in your darkroom... By flushing the developer out with water under a little pressure or flow, one is assured of a kinder, gentler end to development. I simply leave the tank full of developer, and begin pouring water in through a funnel into the neck of the Paterson tank. This way, the water replaces the devloper, and the developer is not left clinging to the film in uneven layers, which can happen when the tank is emptied and allowed to drain before the next step. This developer clinging to the film can cause uneven development. Troll nonsense. Developer simply continues to develop until exhausted. Doesn't cause "uneven" development, since the negative density controls the effect. Uneven coating of developer will certainly cause streaking, as would occur when stop bath is splashed onto the film that still has areas that are wet with developer. One does not "splash." One immerses. As the tank fills, it splashes a little. Also, with either a water rinse or an actual stop bath diffusion should occur at the same rate. Being acidic, stop bath works quicker by neutralizing developer _alkalinity_ and thus has the advantage of preventing carry over. I rinse the film thoroughly with lots of water that displaces and replaces the developer over about 7 seconds. The point is that the change-over is more uniform, because the water does not arrest development instantly, but smoothly. Sorry. Diffusion takes at least 30 seconds and the developer continues to be active in thin (less dense) areas of the negative. Development in the emulsion is not arrested ("smoothly" or any other way) by dilution, but simply continues to develop until exhausted. That's exactly what I mean by 'smoothly'. I begin filling the tank with water about 45 seconds before development is to end. The deevloper is NOT poured out of the tank; the water simply displaces it. |
#35
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#36
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On Thu, 11 Nov 2004 00:03:28 +0000, Andrew McCall
wrote: Hi Folks, The college I go to have recently decided not to use a stop bath when developing film as the gasses it produces seems to agitate some students with asthma. Can anyone tell me why it would do this to the asthma suffers, ie. what gasses are given off by the stop bath? .... nov2304 from Lloyd Erlick, I think the college would do well to switch to non-acid film and print processing for black and white. This would eliminate any gasses that the common darkroom might emit. The main gasses and 'fumes', not to mention stenches, that afflict the darkroom are acetic acid (smells like vinegar), sulfur dioxide (bites nose sharply), and hydrogen sulfide (rotten egg smell). If acid is removed from the darkroom, none of these can come into existence. The mechanism by which sulfur dioxide and hydrogen sulfide harm humans (and no doubt asthma sufferers react to much less exposure than it takes to harm a non-asthmatic) is: both gasses dissolve readily in water. Human lungs and breathing passages are coated with mucous, which contains a large proportion of water. Thus, the gas dissolves in water in the lungs, whereupon it reacts to form sulfurous acid. The lungs are full of air, containing lots of oxygen, and sulfurous acid oxidizes readily, to form sulfuric acid. If enough gas is present in the atmosphere being breathed, enough acid will form to damage tissue. A very important point about hydrogen sulfide: humans can detect the odor of extremely small amounts. The smell is very distinctive, and we detect it at levels far below dangerous. However, it is possible to ignore the warning and become complacent if we stop detecting the odor. This can be a very important danger sign, because it appears the action of hydrogen sulfide upon the olfactory sense organ is numbing or deadening (probably the effect of sulfuric acid). People have died in mines because they thought the gas had gone away, when in fact their own sensory input had gone. If people are sensitive enough that even ammonia must be eliminated, it only means that selenium toner cannot be used or must be used with special care. Ammonia is very easy to deal with by ventilation, and also it's easy to keep selenium toner under cover except for the moment needed to put the sheet into it, (or pour it onto the sheet). I have some articles on my website (under the technical heading, in the table of contents) about smell/fume abatement in the darkroom, as well as the single tray method of processing prints and odorless fixers. I think anyone with asthma who would like to work in the darkroom should look them over. regards, --le ________________________________ Lloyd Erlick Portraits, Toronto. voice: 416-686-0326 email: net: www.heylloyd.com ________________________________ ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#37
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On Thu, 11 Nov 2004 00:03:28 +0000, Andrew McCall
wrote: Hi Folks, The college I go to have recently decided not to use a stop bath when developing film as the gasses it produces seems to agitate some students with asthma. Can anyone tell me why it would do this to the asthma suffers, ie. what gasses are given off by the stop bath? .... nov2304 from Lloyd Erlick, I think the college would do well to switch to non-acid film and print processing for black and white. This would eliminate any gasses that the common darkroom might emit. The main gasses and 'fumes', not to mention stenches, that afflict the darkroom are acetic acid (smells like vinegar), sulfur dioxide (bites nose sharply), and hydrogen sulfide (rotten egg smell). If acid is removed from the darkroom, none of these can come into existence. The mechanism by which sulfur dioxide and hydrogen sulfide harm humans (and no doubt asthma sufferers react to much less exposure than it takes to harm a non-asthmatic) is: both gasses dissolve readily in water. Human lungs and breathing passages are coated with mucous, which contains a large proportion of water. Thus, the gas dissolves in water in the lungs, whereupon it reacts to form sulfurous acid. The lungs are full of air, containing lots of oxygen, and sulfurous acid oxidizes readily, to form sulfuric acid. If enough gas is present in the atmosphere being breathed, enough acid will form to damage tissue. A very important point about hydrogen sulfide: humans can detect the odor of extremely small amounts. The smell is very distinctive, and we detect it at levels far below dangerous. However, it is possible to ignore the warning and become complacent if we stop detecting the odor. This can be a very important danger sign, because it appears the action of hydrogen sulfide upon the olfactory sense organ is numbing or deadening (probably the effect of sulfuric acid). People have died in mines because they thought the gas had gone away, when in fact their own sensory input had gone. If people are sensitive enough that even ammonia must be eliminated, it only means that selenium toner cannot be used or must be used with special care. Ammonia is very easy to deal with by ventilation, and also it's easy to keep selenium toner under cover except for the moment needed to put the sheet into it, (or pour it onto the sheet). I have some articles on my website (under the technical heading, in the table of contents) about smell/fume abatement in the darkroom, as well as the single tray method of processing prints and odorless fixers. I think anyone with asthma who would like to work in the darkroom should look them over. regards, --le ________________________________ Lloyd Erlick Portraits, Toronto. voice: 416-686-0326 email: net: www.heylloyd.com ________________________________ ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#38
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Lloyd Usenet-Erlick wrote: On Thu, 11 Nov 2004 00:03:28 +0000, Andrew McCall wrote: Hi Folks, The college I go to have recently decided not to use a stop bath when developing film as the gasses it produces seems to agitate some students with asthma. Can anyone tell me why it would do this to the asthma suffers, ie. what gasses are given off by the stop bath? ... nov2304 from Lloyd Erlick, I think the college would do well to switch to non-acid film and print processing for black and white. This would eliminate any gasses that the common darkroom might emit. The main gasses and 'fumes', not to mention stenches, that afflict the darkroom are acetic acid (smells like vinegar), sulfur dioxide (bites nose sharply), and hydrogen sulfide (rotten egg smell). If acid is removed from the darkroom, none of these can come into existence. The mechanism by which sulfur dioxide and hydrogen sulfide harm humans (and no doubt asthma sufferers react to much less exposure than it takes to harm a non-asthmatic) is: both gasses dissolve readily in water. Human lungs and breathing passages are coated with mucous, which contains a large proportion of water. Thus, the gas dissolves in water in the lungs, whereupon it reacts to form sulfurous acid. The lungs are full of air, containing lots of oxygen, and sulfurous acid oxidizes readily, to form sulfuric acid. If enough gas is present in the atmosphere being breathed, enough acid will form to damage tissue. This is a very informative description. However, I think also overstated for the typical darkroom. I know of no photographer who has suffered adverse damage or illness from exposure to typical mild acid chemistry. Ansel Adams, Richard Avedon, etc. etc., lived long and healthy lives and died of old age William Henry Jackson handled photo chemicals from the collodion era to the modern era (1870s to early 20th century) and enjoyed a remarkably healthy life of over 90 years. Now, some (as yourself) may be more sensitive to mild acid fumes and byproducts than most. I have no problem with offering alternate methods. But you make it sound as if this is a serious health hazard and statistically significant. It's not. Acid rain is more of a hazard; it kills trees and fish but isn't very harmful to humans. I think it should be pointed out the typical darkroom using an acid process (especially with rapid fix) is not a unhealthy environment and if the fumes bother more sensitive people it's an indication the room in fact has inadequate _ventilation_, which for a school darkroom probably violates OSHA standards. What bothers me about most of these discussions is some who religiously advocate alkaline vs acid also claim a virtue of alkaline is no ventilation is needed. _Any_ darkroom should receive a minimum of about 6-8 air changes per hour (once every ten minutes, and if a commerical or school darkroom probably more. This will eliminate most if not all chemistry issues unless one actually sticks their nose in the stop/fixer. A very important point about hydrogen sulfide: humans can detect the odor of extremely small amounts. The smell is very distinctive, and we detect it at levels far below dangerous. However, it is possible to ignore the warning and become complacent if we stop detecting the odor. This can be a very important danger sign, because it appears the action of hydrogen sulfide upon the olfactory sense organ is numbing or deadening (probably the effect of sulfuric acid). People have died in mines because they thought the gas had gone away, when in fact their own sensory input had gone. If people are sensitive enough that even ammonia must be eliminated, it only means that selenium toner cannot be used or must be used with special care. Ammonia is very easy to deal with by ventilation, and also it's easy to keep selenium toner under cover except for the moment needed to put the sheet into it, (or pour it onto the sheet). I have some articles on my website (under the technical heading, in the table of contents) about smell/fume abatement in the darkroom, as well as the single tray method of processing prints and odorless fixers. I think anyone with asthma who would like to work in the darkroom should look them over. regards, --le ________________________________ Lloyd Erlick Portraits, Toronto. voice: 416-686-0326 email: net: www.heylloyd.com ________________________________ ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
#39
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Lloyd Usenet-Erlick wrote: On Thu, 11 Nov 2004 00:03:28 +0000, Andrew McCall wrote: Hi Folks, The college I go to have recently decided not to use a stop bath when developing film as the gasses it produces seems to agitate some students with asthma. Can anyone tell me why it would do this to the asthma suffers, ie. what gasses are given off by the stop bath? ... nov2304 from Lloyd Erlick, I think the college would do well to switch to non-acid film and print processing for black and white. This would eliminate any gasses that the common darkroom might emit. The main gasses and 'fumes', not to mention stenches, that afflict the darkroom are acetic acid (smells like vinegar), sulfur dioxide (bites nose sharply), and hydrogen sulfide (rotten egg smell). If acid is removed from the darkroom, none of these can come into existence. The mechanism by which sulfur dioxide and hydrogen sulfide harm humans (and no doubt asthma sufferers react to much less exposure than it takes to harm a non-asthmatic) is: both gasses dissolve readily in water. Human lungs and breathing passages are coated with mucous, which contains a large proportion of water. Thus, the gas dissolves in water in the lungs, whereupon it reacts to form sulfurous acid. The lungs are full of air, containing lots of oxygen, and sulfurous acid oxidizes readily, to form sulfuric acid. If enough gas is present in the atmosphere being breathed, enough acid will form to damage tissue. This is a very informative description. However, I think also overstated for the typical darkroom. I know of no photographer who has suffered adverse damage or illness from exposure to typical mild acid chemistry. Ansel Adams, Richard Avedon, etc. etc., lived long and healthy lives and died of old age William Henry Jackson handled photo chemicals from the collodion era to the modern era (1870s to early 20th century) and enjoyed a remarkably healthy life of over 90 years. Now, some (as yourself) may be more sensitive to mild acid fumes and byproducts than most. I have no problem with offering alternate methods. But you make it sound as if this is a serious health hazard and statistically significant. It's not. Acid rain is more of a hazard; it kills trees and fish but isn't very harmful to humans. I think it should be pointed out the typical darkroom using an acid process (especially with rapid fix) is not a unhealthy environment and if the fumes bother more sensitive people it's an indication the room in fact has inadequate _ventilation_, which for a school darkroom probably violates OSHA standards. What bothers me about most of these discussions is some who religiously advocate alkaline vs acid also claim a virtue of alkaline is no ventilation is needed. _Any_ darkroom should receive a minimum of about 6-8 air changes per hour (once every ten minutes, and if a commerical or school darkroom probably more. This will eliminate most if not all chemistry issues unless one actually sticks their nose in the stop/fixer. A very important point about hydrogen sulfide: humans can detect the odor of extremely small amounts. The smell is very distinctive, and we detect it at levels far below dangerous. However, it is possible to ignore the warning and become complacent if we stop detecting the odor. This can be a very important danger sign, because it appears the action of hydrogen sulfide upon the olfactory sense organ is numbing or deadening (probably the effect of sulfuric acid). People have died in mines because they thought the gas had gone away, when in fact their own sensory input had gone. If people are sensitive enough that even ammonia must be eliminated, it only means that selenium toner cannot be used or must be used with special care. Ammonia is very easy to deal with by ventilation, and also it's easy to keep selenium toner under cover except for the moment needed to put the sheet into it, (or pour it onto the sheet). I have some articles on my website (under the technical heading, in the table of contents) about smell/fume abatement in the darkroom, as well as the single tray method of processing prints and odorless fixers. I think anyone with asthma who would like to work in the darkroom should look them over. regards, --le ________________________________ Lloyd Erlick Portraits, Toronto. voice: 416-686-0326 email: net: www.heylloyd.com ________________________________ ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
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