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Photo Forum / Film Photography / Darkroom / November 2004Not using a stop bath when developing film?
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? What are the effects on processing when skipping the stop bath? We are using relatively slow developers like Agfa Rodinal and Ilford Ilfotec DD-X. 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. Thanks, Andrew McCall > Hi Folks, > [quoted text clipped - 16 lines] > > Andrew McCall Stop bath is a mild solution of Acetic acid, about half the strength of white vinegar. It can react with the sodium sulfite in developers to release a small amount of Sulfur dioxide gas. Sulfur dioxide has a sharp odor and can trigger asthma in those afflicted. It can also release Carbon dioxide gas when developers with carbonates are used. There are very few current packaged film developers with carbonate in them but most paper developers have it. Carbon dioxide in these very small amounts is not dangerous or irritating. Nor will it cause pin-holes in modern emulsions. Stop bath is important in stopping development at a definite point but a plain water stop can be used provided its thorough. It should really be a short wash. Thoroughly agitate the film in the water for a minute or more. Carried over developer will react with the acid in the fixing bath the same way it does with the stop bath. Generally, acid fixing baths do emmit some sulphur dioxide gas. The use of a non hardening fixing bath or a neutral bath will eliminate this. Kodak Rapid Fixer with Hardener is reasonably low odor if the hardener is not added. Agfa Universal Fixer, used in color processes, is a neutral pH non-hardening rapid fixer. Odor free stop baths can be made using Citric acid and Sodium bisulfite or metabisulfite. Citric acid stop baths should not be used with hardening fixing baths because the citric acid tends to cause precipitation of the alum hardener. Ilford packaged stop bath concentrate is made from citric acid but citric is also available cheaply from health food stores and for use in home canning. Use about 15 grams per liter for stop bath. This is also about the right amount of Sodium Bisulfite or metabisulfite. Most Sodium bisulfite is actually metabisulfite, they are identical in action in photo solutions. Good ventillation is a necessity for a darkroom.  Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com >Hi Folks, > [quoted text clipped - 15 lines] > >Andrew McCall nov1104 from Lloyd Erlick, Using plain tap water in place of an acid stop bath is common practice. It requires a certain care, but is easy and effective. Personally, I used to enjoy the smell of stop bath. I still like vinegar on my french fries. But eight or ten hours around stop bath, many times, has made me hate all smells in my darkroom. I like an odor free darkroom now. My website has articles about my quest for a smell free zone in my darkroom. The one about non-acid print processing might be of interest (applies to film, too, more or less.) Look under 'technical' in the table of contents. regards, --le Signature________________________________ Lloyd Erlick Portraits, Toronto. voice: 416-686-0326 email: portrait@heylloyd.com net: www.heylloyd.com ________________________________ > Hi Folks, > [quoted text clipped - 11 lines] > if I have to, will developing at college with no stop bath have an > effect on my negatives. Ilford makes a odorless stopbath, which I think is based on citric acid rather then acetic acid. Technically you still have a stop bath, it's just water instead of a diluted vinegar. What I usually did was double the length of the stop, and then reduce the capacity of the fixer to half. I never used a stop bath with film, but 3 20 second water soaks, and then used the fixer 1 shot. Never had a problem. W > I never used a stop bath with film, but 3 20 second water soaks, > and then used the fixer 1 shot. Never had a problem. The use of a stop bath is really not needed for film, in fact there have been "monobath" (combined developer/fixer) products on the market and Edwal used to include instructions on how to use their developers as monobaths. The main reason to use one is to force development to end at a specific time so that the results are the same, but using the same rinse procedure will each time do the same thing (with slightly different results). It's also to keep the alkeline developer from mixing with the acid fixer. The acid in the fixer acts as an emulsion hardner. Some fixers include it, some include it as an option (remember the two bottle kodak rapid fixer with hardner?) and some don't have it at all. Geoff. SignatureGeoffrey S. Mendelson, Jerusalem Israel gsm@mendelson.com IL Voice: 972-544-608-069 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838 > In article > <0rLkd.33324$km5.1592741@news20.bellglobal.com>, The [quoted text clipped - 28 lines] > > Geoff. Its not the acid in the fixing bath that does the hardening. Common fixing baths use Potassium aluminum sulfate, also known as White Alum, or just Alum. The alum hardens the gelatin but works only over a fairly narrow range of pH. The hardening remains at neutral pH but is destroyed at much on the alkaline side of neutral. There are other hardeners, mostly organic compounds, which are effective hardeners in alkaline solution. These are common in color processing. Because the acid in an acid fixing bath reacts with the thiosulfate and eventually decomposes it some means must be provided to protect the thiosulfate. This is usually sodium sulfite. The large amount of sulfite needed also tends to prevent stains from the reaction products of carried over developer. Because modern stop baths were devised to work with or without a stop bath they are heavily buffered by using a combination of Acetic acid and Boric acid. This tends to keep the pH of the bath in the right range for effective hardening despite carried over developer or carried over stop bath. This type of bath also tends to have less problem from sludging of the hardener when the pH is off the right value. It should be noted that the ability of thiosulfate to fix is independant of pH. The odor from fixing baths is due to some decomposition of the thiosufate by the acid. Making the bath less acid will reduce the odor. Neutral fixing baths, essentially just thiosulfate and sulfite, are very low odor. Citric acid or sodium bisulfite or sodium metabisulfite can be used for odorless stop baths. Citric acid is not ideal for use with fixers using alum hardeners because it is a sequestering agent for aluminum and will cause reduction of hardening and may also cause sludging. Many modern films do not require hardening so do not need fixers which are acid. I seen no advantage whatever in making a fixing bath alkaline but making neutral fixer is fine. Also, the swelling of the emulsion will be less in a neutral bath than in either an acid or alkaline bath. There is an advantage in washing if the emulsion is neutral when it it is washed. If an acid hardening fixer is used a buffered sulfite wash aid, like Kodak Hypo Clearing Agent, will adjust the pH to neutral and also eliminate the binding effect of the alum on thiosulfate and fixer reaction products. Wash times when the emulsion is treated in such a bath are the same regardless of the type of fixing bath used. In addition the sulfite acts as an ion exchanger for thiosulfate so the wash is very much accelerated over what one would have from a simple neutralizing bath without sulfite. I still think acid stop baths prevent more problems than they cause but certainly a plain water rinse works if it actually washes out the bulk of the developer. BTW, someone mentioned monobath processing. Much of the research on this was done by Grant Haist. He wrote a small book called _The Monobath Manual_ (very hard to obtain now) and also covers monobaths in his _Modern Photographic Processing_. Monobaths are not simply a mixture of developer and fixer. They must be very carefully formulated and matched to a specific emulsion. They have some very interesting properties, not least of which is very considerable immunity to temperature and time variations. Haist shows some examples suggesting the possible image quality is very high. For some reason monobaths have never become popular except for some special rapid access uses. Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com Richard, Great post as usual. <snip> > Because modern stop baths were devised to work with or >without a stop bath they are heavily buffered by using a >combination of Acetic acid and Boric acid. Perhaps you meant "fixing baths" ? >Monobaths are not simply a mixture of developer >and fixer. They must be very carefully formulated and [quoted text clipped - 4 lines] >quality is very high. For some reason monobaths have never >become popular except for some special rapid access uses. I think it's just as you indicated that they need to be formulated for specific films and I would add that those formulas were used one-shot and probably had limited stability due to the high alkalinity. The formulas that I'm familiar with use hydroxide as an accelerator. Perhaps there are other agents used ? Regards, John S. Douglas, Photographer - http://www.puresilver.org Please remove the "_" when replying via email > Richard, > > Great post as usual. yeah I think he should consider adding a regular joke line to his sig :) Who knew? > <snip> > [quoted text clipped - 3 lines] > > Perhaps you meant "fixing baths" ? Unless one _is_ alkaline I'd use a stop. > >Monobaths are not simply a mixture of developer > >and fixer. They must be very carefully formulated and [quoted text clipped - 15 lines] > John S. Douglas, Photographer - http://www.puresilver.org > Please remove the "_" when replying via email > Richard, > [quoted text clipped - 27 lines] > John S. Douglas, Photographer - http://www.puresilver.org > Please remove the "_" when replying via email Of course, I meant fixing bath although buffered stop baths are also possible and will have a longer life than a plain acetic or citric acid bath. Grant Haist goes quite deeply into monobaths, evidently this was a subject of his research work at Kodak. Many monobaths do use sodium hydroxide as the accelerator, the reason is simple: the developer must compete with the fixer. Development must be completed before enough of he halide is removed to destroy the image. Monobaths must also contain a hardener. Haist has formulas with Glutaraldehyde but also lists a number of oganic hardeners suitable for use in highly alkaline baths. In both of his books Haist shows formulas optimized for Tri-X (roll film) and Verichrome Pan, I think a couple of others but I am away from my books at the moment. At least a couple of these formulas include Phenidone as a primary developing agent. I should point out that the hardener in fixing baths was intended to compensate for the swelling caused by both the alkaline developer and the acid fixer. Auxilliary hardeners are less necessary where the pH of the solutions does not vary from neutral by much. Eliminating the stop bath is attractive but there is still the problem of stopping the development quickly and keeping developer from carrying over to a neutral or alkaline fixing bath where it can continue development. A long rinse in running water seems to be the solution. This is the method used in alkaline color processing. Rinses are typically 1 to 3 minutes. Where highly alkaline developers are used, such as lithographic developers, it is common practice to use an anti-swelling stop bath. Typically this has about 15 grams/liter of Sodium sulfate in it (sulfate not sulfite). Sulfate is also used in tropical developers to reduce emulsion swelling and slow the rate of development. Since many B&W films, for instance T-Max, are now made to withstand 100F processing such measures are not necessary for them. However, films like Tri-X are still relatively sensitive to emulsion swelling. It was also common in tropical processing and lith processing to use a chrome-alum stop bath. Chrome alum is acid and is a very effective hardener. However, it must operate at very low pH (around 2.0) so is difficult to incorporate into fixing baths although there are chrome alum fixing baths. Its use is probably not necessary for any film these days. With all the talk about alkaline processing and eliminating stop baths it seems to have gotten lost that this procedure has been used with completely satisfactory results for many decades. The proper use of an acid stop bath stops development quickly and prevents carryover of active developer into the fixing bath. It also prevents the possible generation of developer stain where it is allowed to continue in a bath without sulfite. It also seems to me than in reading the reasons for not using acid stop baths I am really seeing complaints of problems from bad practice. Even complaints about odor can be solved by using acids other than Acetic acid. Pin holes are extremely unlikely to be caused by any conventional packaged developer or fixer. For one thing modern emulsions are not very vulnerable to it and very few current film developers use carbonate, the villan in outgassing. A pinhole is an actual disruption of the emulsion. I suspect that very often what people are seeing are small clear spots caused by dust on the negative. Pin holes CAN occur because of coating problems. These exist in the emulsion from the manufacturer. A very great deal of research and technical development has gone into making very consistent coatings. This is very well established technology but even the best manufacturers may have problems especially in these days of low sales and cost cutting. Personally, I suspect the whole movement to use alkaline processing is a sort of belief in black magic. Well, folks, there just isn't any black magic in photographic chemistry anymore. Even emulsion making, once one of the most closely guarded proprietary secrets in any industry, are now public record and anyone who is willing to do some research, AND has a decent understanding of organic and colloid chemistry, can find out how its done. Now, watch the flames come:-) Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com > Personally, I suspect the whole movement to use alkaline processing > is a sort of belief in black magic. Well, folks, there just isn't any [quoted text clipped - 8 lines] > Los Angeles, CA, USA > dickburk@ix.netcom.com 1. A test performed in 1966 by Popular Photography magazine showed NO difference between the grain of Tri-X processed with or without a stop bath, magnified under a microscope. 2. I quit using stop bath because I don't think it is the best way to stop development evenly. For about 10 years now I simply pour several large containers of tempered water into my Paterson tanks and flush the developer out. I never have streaks anymore, which I sometimes experienced with stop bath. > 2. I quit using stop bath because I don't think it is the best way to > stop development evenly. For about 10 years now I simply pour several > large containers of tempered water into my Paterson tanks and flush > the developer out. I never have streaks anymore, which I sometimes > experienced with stop bath. Eddie Ephraums has suggested a water rinse prior to an acid stop. IIRC, his concern is with reticulation. Of course the rinse will remove some developer, and dilute and neutralize that which remains. Short acid stops are recommended by Ilford and Kodak. They will confer upon and to some small extent within the emulsion the acidity needed to maintain the acid fix. I've been reviewing Dr. Gudzinowicz's evaluation of water vs acid "stops". Of course he goes on and on some what. Search this NG for, 3.8 4.8 5.8 pka to assess at least one treatise of his on that subject and associated matters. Dan > > 2. I quit using stop bath because I don't think it is the best way to > > stop development evenly. For about 10 years now I simply pour several [quoted text clipped - 12 lines] > NG for, 3.8 4.8 5.8 pka to assess at least one treatise > of his on that subject and associated matters. Dan 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. 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. This method may not work with stainless steel tanks, because there is no flow-through mechanism in them. http://www.patersonphotographic.com/accessories/page3.html http://www.jjmehta.com/products/paterson_tanksprial.html The Paterson tank allows the solution to go down the center tube and fush out the sides. > > > 2. I quit using stop bath because I don't think it is the best way to > > > stop development evenly. For about 10 years now I simply pour several [quoted text clipped - 16 lines] > 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 [quoted text clipped - 4 lines] > 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. 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. > This method may not work with stainless steel tanks, because there is > no flow-through mechanism in them. [quoted text clipped - 5 lines] > The Paterson tank allows the solution to go down the center tube and > fush out the sides. > > 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 [quoted text clipped - 14 lines] > 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. > 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. > > This method may not work with stainless steel tanks, because there is > > no flow-through mechanism in them. [quoted text clipped - 5 lines] > > The Paterson tank allows the solution to go down the center tube and > > fush out the sides. > > > > > The problem as I see it is that when the stop bath hits the film in a [quoted text clipped - 19 lines] > 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 [quoted text clipped - 6 lines] > 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. > > > > > > > The problem as I see it is that when the stop bath hits the film in a [quoted text clipped - 21 lines] > > 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 [quoted text clipped - 12 lines] > 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. > That's exactly what I mean by 'smoothly'. I begin filling the tank > with water about 45 seconds before development is to end. The > developer is NOT poured out of the tank; the water simply displaces > it. And the film comes out alive? Imagine that! Tell me then what's all this talk of instantly stoping development? Just so much baloney? Some contributors to this NG imply by their posts that an instant stop is THE virtuous stop. Dan >Well, folks, there just isn't any >black magic in photographic chemistry anymore. Doggone it ! Ansel beat me to all that Black Magic developer !! Regards, John S. Douglas, Photographer - http://www.puresilver.org Please remove the "_" when replying via email > There are other hardeners, mostly organic compounds, > which are effective hardeners in alkaline solution. Now days the integrity of incorporated hardeners is more of a concern. Most B&W processing is done without hardeners added to the chemistry. Developers can be very alkaline. Have you any idea just how alkaline they can be and not degrade the film's or paper's incorporated hardener? I've a notion that most films and papers are pre-process hardened as fully as any in-process hardener will do, even more so. Is that notion correct? Perhaps pre-process hardening is less than if there were none and the hardening left to an in-process hardener. Maybe a combination of the two would result in the most hardened emulsion possible. What do you think? Dan My own practice is to use a water rinse when processing film between the developer and fix, since this is one-shot it will stop development almost as effectively as an acid stop. For printing in trays, developer carry-over will render a water stop bath alkaline in short order at which point you are no longer stopping development but doing stand development in a two bath developer! Did this by accident one time (diluted Dektol stock 1+31 in my stop bath tray instead of acetic acid--really tired that night) and got some interesting results, if you leave prints in the diluted "stop" tray for extended periods of time, sort of Sabattier but weak and orange-ish highlights, standard practice in this darkroom was to let prints pile up in the stop bath and then fix them in batches before moving out of the darkroom to the big Pako Washer. Signaturedarkroommike ---------- > Hi Folks, > [quoted text clipped - 15 lines] > > Andrew McCall > 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. try this healthy combination: rinse your film for about 60" in plain water. It's ok, and it's what I do. Never needed stop bath. Ciao, Stefano SignatureNon ? bello cio che ? bello figuriamoci cio che ? brutto! Ed io imparo. > Hi Folks, > [quoted text clipped - 5 lines] > 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 >Hi Folks, > [quoted text clipped - 4 lines] >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 Signature________________________________ Lloyd Erlick Portraits, Toronto. voice: 416-686-0326 email: portrait@heylloyd.com net: www.heylloyd.com ________________________________ > >Hi Folks, > > [quoted text clipped - 33 lines] > 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 [quoted text clipped - 35 lines] > 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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