That might be dichroic fog. Search this thread, and you'll find a few recommendations.
Monobath processing seems to be very convenient, using only a single solution, and could be a good way of introducing film processing to beginners.
However after a bit of research and experimenting, jumping off from Ben-S’s use of Ilford LC-29 and Ilford Rapid Fixer, I’m not so sure it’s worth reviving this old thread, but perhaps it may nevertheless worth recording something.
Donald Quall’s 1+15 HC-110 formula has about a 1+24 concentration of rapid fixer; Ben-S’s 1+19 LC29 formula includes 1+20 rapid fixer. At these dilutions, fixing takes a long time, similar to what Bill Troop says about sodium thiosulfate monobaths in The Film Developing Cookbook, i.e., development may be complete in 3 minutes but fixing may take 4 to 7 minutes. Troop doubts whether sodium thiosulfate fixing is satisfactory for modern films rich in iodide, but says he has not found any formulas for ammonium thiosulfate monobaths, which would have to be “exceedingly rapid.” They are indeed rare. The superspeed monobaths in post 80 above all use sodium thiosulfate.
I don’t have access to Grant Haist’s Monobath Manual, but in Modern Photographic Processing Haist only refers to but does not reproduce Jerome Goldhammer’s US patents 2,782,121 and 2,782,120 (both 1957). Here is one of Goldhammer’s formulas:
Water (120 degrees F [50C] 750 cc
Sodium sulfite (anhydrous) 50 g
Amidol 15 g
Pyrocatechol 15 g
Potassium bromide 5 g
Sodium hydroxide 25 g
Ammonium thiosulfate 50 g
Water to make 1000cc.
pH = 9.3. Time 3 minutes at 68F [20C]. Gamma on high speed panchromatic films 0.85.
Goldhammer’s applied for the patent for this monobath in 1954, before Keelan’s major advance of 1957, introducing Phenidone to monobaths (and thus emulsion speed maintenance, rather than loss). Thus, Goldhammer uses Amidol instead to initiate rapid development (although it's probably too expensive to contemplate using now, as an aside, it's interesting to note that for the first time Goldhammer claims to have made Amidol stable, in the presence of a small amount of Hydroquinone, Pyrocatechol, or similar developing agents). Goldhammer criticized Keelan’s earlier Metol/Hydroqinone monobaths for their excessive salt content, and advocated moving to an ammonium based system. However in a later patent (2,901,350/1959), Goldhammer abandoned ammonium thiosulfate for amines, because the liberated ammonia odor, although only a “slow” cause of deterioration in a deep tank, caused problems and was considered objectionable with shallow tray usage, at high room temperatures, or at low atmospheric pressures, as in an aircraft [remember that many monobaths were formulated for aerial surveillance work; both Keelan and Levy were directly funded by the US Air Force] or at high altitudes. Goldhammer thus returned to sodium thiosulfate as his fixing agent (Haist MPP 179), although in at least one formula he also adds a small amount of sodium thiocyanate, probably more as a silver solvent for fine grain rather than to speed up fixing.
As an aside, note that thiocyanate is sometimes added to sodium thiosulfate to make a more rapid fixer than sodium thiosulfate on its own. Haist, p. 171 gives a 1964 Fuji thiocyanate monobath formula, which although it claims “effective emulsion speed”, is probably optimized more for fine grain rather than speed. An additional possible disadvantage of thiocyanate for this purpose may be its tendency to soften gelatin.
G. P. Ham’s US Patent 2,230,977/1941, example 5, substitutes 25g/l ammonium thiosulfate for the equivalent amount of sodium thiosulfate in his first example (cf. Haist, 178 for a related formula). The substitution supposedly yields a similar result. A.A. Newman, in his review of monobaths (BJP 1959:47) comments that although clean working, Ham’s processing times are very long (10 minutes in this case); and with 2.5% w/v fixer content, “exhaustion characteristics … cannot be more than fair.”
Marilyn Levy’s US Patent 3,167,429/1965 example 8 has 50g/l ammonium thiosulfate. There may well be others, but in general later researchers such as Haist tended to move away from thiosulfates to organic fixers in order to eliminate sludging.
As previously noted in this thread, monobaths involve something of a competition between developing and fixing. Quoting his own Monobath Manual in Modern Photographic Processing (194), Grant Haist summarizes how to adjust the activity of a monobath as follows:
To increase Contrast and Emulsion Speed
1. Make the solution more alkaline.
2. Increase the quantity or use more active developing agents or superadditive combination of agents.
3. If more contrast is needed, increase the quantity of hydroquinone or ascorbic acid present in the solution. If more emulsion speed is required, increase the concentration of Phenidone or Metol in the monobath.
4. Raise the processing temperature, if possible, because the gain in the rate of development is greater than the gain in the rate of fixation with higher temperatures.
5. Reduce the amount of fixing agent present, if possible, although the minimum amount of the fixer must be sufficient to clear the film in the desired time of processing.
To Lower Contrast and Reduce Emulsion Speed
1. Increase the quantity of the fixing compound or utilize more active fixing agents.
2. Lower the alkalinity of the solution, as the developing action will be decreased significantly, but the fixing rate of many compounds will be relatively unchanged.
3. More vigorous agitation increases both the rates of development and fixation, but the clearing rate will be accelerated more than development.
It seems to me that trying to speed up monobath development with ammonia, although possibly suitable for amine-based products like HC-110 or LC-29, may not be such a good idea. In his discussion of developer constituents, Haist notes that ammonia is only rarely used in developers because of its volatility and silver solvency; amines are preferable, and “are especially useful for combined developer-fixers where rapid image formation is vital if emulsion speed losses are to be minimized” (250). The concentrated ammonia I have requires very good darkroom ventilation or working outdoors, which isn’t appropriate in the middle of winter, so I’d really rather not go down this path. HC110 and LC29 already contain amines anyway, so I wondered if perhaps a stronger concentration might provide a better solution.
Sodium hydroxide also seemed worth exploring as an alternative alkali, but it needs to be handled with care, and a large amount may soften the emulsion, requiring formaldehyde hardening, which is probably best avoided.
I initially experimented with varying concentrations of LC-29 and rapid fixer, which didn’t seem to work all that well until I added 1g of sodium ascorbate to my ca. 100 ml of solution (equivalent to 10g/litre). However it seemed to make a single test frame of 35mm Ilford HP5+ film quite grainy (in retrospect, this may have been reticulation).
A second series of experiments with increasing amounts of sodium hydroxide gradually increased density, but I didn’t get a normal looking neg until I also added sodium ascorbate. Very high amounts of sodium hydroxide seemed to liberate an ammonia smell anyway (from degradation of the fixer?). My final attempt had LC-29 10ml (1+4); rapid fixer 3.3 ml (1+14); 0.6g sodium hydroxide (equivalent to 12g/litre); 0.25g sodium ascorbate (equivalent to 5g/litre).
At this stage I decided that Ilford rapid fixer probably wasn’t such a good idea either. According to the relevant Ilford fact sheet, the pH of both the 1+4 and 1+9 dilutions is 5.0–5.5. Assuming its formulation is similar to Donald Alnutt’s ATF-1, the acidity is probably due to around 9 ml/l of glacial acetic acid at the 1+4 (or 1+9?) working dilution. It would be better to leave this out, or not to have to neutralize this. The cost of shipping Photographer’s Formulary TF-4 alkaline ammonium thiosulfate rapid fixer to Australia rules it out, and I didn’t think it was worth specially ordering ammonium thiosulfate from Melbourne, so I switched to sodium thiosulfate, and found it relatively easy to formulate a working monobath. Following Crawley, I was going to experiment with 60-120g/l sodium thiosulfate (presumably crystalline), or in my case an equivalent of 40-80g/l of anhydrous sodium thiosulfate. However with 20 ml of LC29 (1+4), 4g of sodium thiosulfate and 1.5 g sodium ascorbate in 100ml I got reasonably good negs in about 5 minutes at around 20C, so I haven’t tried varying the amount of sodium thiosulfate.
I would be nice to speed up the processing time to around three minutes, which might be possible with these ingredients, in increased concentrations, at around 25ºC. I also wondered if my test exposure was about a stop overexposed. In a further test of a few frames, for which I increased the amount of ascorbate to 2g and the temperature to 25C, I got perhaps slightly underexposed and slightly contrasty, but printable negatives. Maybe Phenidone previously dissolved into a stock solution would be better than ascorbate, which I used partly because it dissolves quickly, it’s cheap, and I have a lot of it. However I suspect it’s going to be hard to match the properties of the original developer as a separate solution.
A more general potential drawback (referred to by Troop) may be the archival status of sodium thiosulfate monobath fixing. I strongly suspect Ben’s “creamy” negs (referred to above) may be less than fully cleared. (Incidentally, any solution containing ammonia is also going to have very poor keeping properties, so Ben's speculation about re-use is probably moot). Clearing to completion in a highly dilute (near exhaustion?) fixer may not necessarily represent adequate fixation. The normal rule is that fixing time should be double (Troop says triple) the clearing time. Clearing time is harder to judge with monobaths, as you can’t check it with the lights on. Inadequate monobath fixing can thus be considered analogous to stabilization processing. Leaving the film in a monobath solution for an extended time may be an option (etching the image silver is likely to take awhile at this dilution), but I suspect it may increase the chances of any remaining insoluble silver thiosulfate complexes being absorbed by the gelatin of the emulsion. The theory behind two-bath fixation is that the fresh second bath converts “most, though not necessarily all, the silver thiosulfate to the silver dithiosulfate ion, which is then removable by washing with water” (Haist 564). Alternatively, you could re-fix the negative you want to keep in fresh fixer, but then you lose the benefits of monobath processing.
As a follow on, if Bill Troop ever gets around to revising The Film Development Cookbook (presumably under another title, and with another collaborator), the Crawley monobath formula should be identified as FX-6a. Crawley originally published it in 1961 as FX-6, which differs only in that it starts off with an additional 1g of Metol. Crawley later decided the speed increase conferred by the Metol was only slight, and for the sake of economy it could be omitted. However in addition to Crawley’s suggestion of increasing the hydroquinone to 15-17 g to increase contrast (as noted by Ian Grant in #27 above), adding Metol may also be a useful additional control for anyone trying to tweak this formula for a particular film. Crawley also says FX-6a can be “divided into two stock solutions: (A) developing agents and sulfite, (B) hypo. On mixing, add one pellet [?] of sodium hydroxide per working ounce [28.4cc]; this is quite accurate enough, and may be used always when making up the solution.” The pellet recommendation may require an alternative teaspoon conversion, but separate stock solutions may be a good way of overcoming sludge problems, unfortunately at the price of economy.
The only other recent monobath formula created by a photographer I’ve come across is the 1996 formula given in Kevin M. Pernicano’s “Monobaths: Simultaneous Development & Fixation,” Photo Techniques (USA), Vol. 21, No. 1, Jan-Feb 2000, pp. 44-46 (back issue available from http://www.phototechmag.com/). This seems to be a fairly low activity formula (incidentally, erythorbic acid = isoascorbic acid). It appears to take about 10 minutes and work best with T-Max 100 and Delta 400, which both yield a speed loss only one stop below the manufacturer’s E.I. (Pernicano says exposures indices can be raised about one stop with a one minute 1% sodium perborate presoak). Pernicano’s formula has 15 g ammonium chloride with its 75 g sodium thiosulfate, which may represent an attempt to formulate a more rapid sodium thiosulfate fixer, or perhaps the ammonium chloride is a solvent for fine grain which is depressing speed. It is available commercially from http://www.kyantec.com/photographic.htm.
Perhaps the last researcher to patent monobath formulas is Alan S. Fitterman and his colleagues from Kodak, who from the late 1990s to the early 2000s seem to have been developing an innovative room light processing kit for dental X-rays. See, for example, US Patent 6,022,675 / 2000 for a yellow dye containing monobath that provides safelight processing conditions for the solution by absorbing light between about 350 to 500nm. The example 1 formula in this patent also uses a combination of sodium thiocyanate and sodium thiosulfate as the fixing agent:
Hydroquinone 220 mmol/l [24.2 g/l]
Benzotriazole 0.5 mmol/l [0.6 g/l
[Dimezone] 24.2 mmol/l [4.6 g/l]
Sodium sulfite 320 mmol/l [40.3 g/l]
Sodium thiocyanate 740 mmol/l [60 g/l]
Sodium thiosulfate 630 mmol/l [99.6 g/l]
My conversions to g/l may not be absolutely accurate; I’m also assuming 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone = Dimezone, mol wt 190.18, which I’ve got wrong before. Sodium hydroxide may also be required to adjust to pH 11, and possibly a sodium carbonate buffer. Development times are claimed to be 1 minute, followed by 1 minute wash.
Although there is a certain amount of repetition and redundancy in some of Fitterman’s patents (e.g. separate patents for the use of ascorbic acid or hydroquinone), there are a few interesting ideas in patents for processing devices (6087078, 5956539, 5932398, 5984538, 6082909), cysteine fixing (6074806) and incorporated developing agents with a fixing agent in the activator solution (7147996). Fitterman also has a bob each way between monobaths and what he calls “two stage processing” (5871890). In 7147996 he gives the following fixer as an alternative to a combined ammonium/sodium thiosulfate formula (I’m not sure why you’d use both?):
Cysteine hydrochloride 0.3 mol/l [52.7 g/l]
Sodium hydroxide 0.25 mol/l [10 g/l]
Sodium sulfite 0.05 mol/l [6.3 g/l]
Acetic acid 0.05 mol/l [3 g/l]
I don’t understand why this formulation uses both acetic acid and sodium hydroxide unless perhaps it is intended to make the solution stable. There should be no need to make the solution acidic in order to stop development. According to Grant Haist, who did the original research on it, cysteine works best in alkaline solutions at pH 10.5 (MPP chapter on fixing, p. 602); it is the most rapid film clearing agent, and unlike a lot of the other mercaptos, it is odorless and non-toxic. It probably needs no more than about a minute’s rinse at the washing stage. It sounds too good to be true! Possible disadvantages may be stability (Cysteine becoming Cystine in solution?) and cost (I refused to pay $27.50 for 75 g at my local health food store; ascorbic acid is significantly cheaper). I don’t have any information as to whether cysteine has any detrimental effects on gelatin (softening?) or the developed silver image (bleaching). In an application preempting Fitterman's "two-stage processing", Haist, p.604-5 cites a 1964 patent for the use of a related compound: the addition of 2.5 ml (for every 100ml of developer) of an alkaline 30% solution of a mercapto pyrimidine (probably very smelly, compared to cysteine) “instantaneously stopped” and then fixed (15 seconds vs 40 seconds for a 0.3 mole/liter solution of ammonium thiosulfate) a film developed in a 1:100 solution of Agfa Rodinal. If fixers no longer need to be acidic to stop development or facilitate hardening, is it cost or inertia that keeps us using thiosulfates?
In his article on the “Rise and the Fall of the Monobath” in the British Journal of Photography Annual for 1972, Neville Maude says good results with monobaths have usually “been achieved by experts who would have been at least as successful with conventional processing.”
I think I’m going to go back to “two-stage processing”: adding rapid fixer concentrate (or maybe Cysteine?) to a dilute developer when I’m in a rush and only have one film to develop. At least you’re on slightly safer ground by being able to test clearing time afterwards by placing a film end in the used solution to check that the film is properly fixed.
Definitely. Thanks for the detailed post!
Originally Posted by Philip Jackson
Philip have you read the Neville Maude article "The Rise & Fall of the Monobath" (I mistakenly thought it was by Crawley much earlier in the thread). I did copy it and send it to David Goldfarb, not sure if it's on my laptop or a PC back in the UK, I think the Patrick Dignam article was possibly culled from it.
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Looks like you are making Sodium acetate in situ, probably to act as a buffer
I don’t understand why this formulation uses both acetic acid and sodium hydroxide unless perhaps it is intended to make the solution stable
"Flatter Me, and I May Not Believe You. Criticize Me, and I May Not like You. Ignore Me, and I May Not Forgive You. Encourage Me, and I Will Not Forget You."
I've seen commercial fixer formulae that use Acetic acid and Sodium Hydroxide, it's probably more economic than using Sodium Acete, so cheaper to manufacture.
Thanks to Aurum and Ian Grant for the clarification regarding acetic acid and sodium hydroxide forming a sodium acetate buffer.
Ian, I do have a copy of the Neville Maude article, and recommend it for anyone researching on monobaths, along with the relevant chapter of Haist's Modern Photographic Processing.
I do hope somebody will be encouraged to try cysteine hydrochloride as an alternative fixer.
Since my last burst on monobaths, I’ve managed to get hold of a library copy of Grant Haist’s Monobath Manual (1966). The illustrations refute the allegation that monobaths invariably produce poor image quality (e.g. the reference to excessive grain in post #20 above), although of course monobaths do need to be matched to a specific film (cf. #22 above).
If the fixed contrast automatically produced by combined developer-fixer solutions is considered a disadvantage, Haist includes a brief discussion of split monobaths (or two-stage processing) on pages 94-95.
This involves adding ammonium thiosulfate fixer concentrate to the developer after the completion of development (as discussed in the thread above).
In his discussion of split monobaths, Haist writes that Agfa Combifix, FR Instant Fixol, and Edwal Hi-Speed Liquid Fix Concentrate were specifically marketed (presumably in the mid-1960s) for addition to dilute film developers after the completion of normal development. Haist summarises Edwal’s “Controlled Monobath” Method , which proposed the use of Edwal FG7 diluted 1:15 with water for normal development, followed by the addition directly to the developer of 1 oz of Edwal Hi-Speed Liquid Fix Concentrate (a non-hardening ammonium thiosulfate solution) for each pint of working solution. Edwal warned that image uniformity will suffer unless the fixing additive and the developer can be rapidly and completely mixed. Even vigorous agitation and pouring of a small amount of developer may produce unacceptable results. Haist also noted an appreciable amount of fog with high speed films.
Perhaps proportionally more fixer might prevent fog, and pouring the developer off into a jug which already contains the fixer concentrate (some developer may need to be discarded to avoid overfilling the tank), then pouring the combined developer-fixer back into the developing tank, might ensure better mixing to overcome the image uniformity problems.
The claim in post #3 above, “The amount [of fixer] to add is no less than 1/16 the amount of developer” sounds a bit like a pseudo-scientific rule based on a number plucked out of the air. Given that film fixer is generally used at 1+4, the 1/16 recommendation seems a little low. In any case, the amount of fixer concentrate needed to stop development and effect satisfactory fixation is going to vary depending on the developer and the film. Highly dilute developers and slower old fashioned thin emulsion films are likely to require less fixer for a reduced amount of time.
Perhaps a generalization about the amount of fixer required could be made for an average development time, given that most developers are designed for between 5 and 10 minutes (anything less and uniformity suffers; anything more and it starts to get boring). However unless someone has actually done the work, individual testing would a better approach.
Probably the only disadvantages of the addition of too much fixer would be that it is wasteful, and at an extreme concentration, the fixer might act as a reducer. However too little fixer could turn your developer into a monobath, rather than immediately tipping it over the hump between developing and fixing. Thiosulfate monobaths, according to Haist (MM 74-75), continue “to deposit image silver even after the film has been cleared completely by the action of the thiosulfate. Indeed, developed silver images left in a used thiosulfate monobath will continue to become more massive with the passing of time until much more silver has been deposited than was present in the original silver coverage of the unprocessed film. Needless to say, large granularity increases result from any prolonged processing time in a thiosulfate monobath.”
In other words, split monobaths or two-stage processing might save time, but you still can’t be too slapdash if you want to maintain quality.
Oh no, not pseudo-scientific! Maybe just a bit of kitchen-sink chemistry...
Originally Posted by Philip Jackson
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