Stöeckler, Thornton and contrast control

I have been using both the Stöeckler two-bath developer, and Barry Thornton's variant of it ("Edge of Darkness"), and come to like the latter very much.

However, I have feeling of beig not entirely in complete control to an automatic process that seems to provide good results, but nevertheless: without my complete control. It works, it provides the results that the litterature says it should, but I am somewhat confused as to how Stöeckler (or any metol-based two-bath developer of similar kind) actually works.

Thornton was chasing sharpness (accutance) in his book "Edge of Darkness". He claimed that regarding filmspeed and development times generally that nominal filmspeed is too high and nominal development times are to long (= loss of shadow detail and too much contrast). His advice was to overexpose by 1 to 1 1/2 stops and underdevelop about 30% less than nominal time, which gives finer grain and better shadow detail etc. This is all fine, and I think I understand the principles. However, although this is a fundamental principle in Thornton's practice, he never says anything about how he underdevelops by 30% with his 2-bath Stöeckler variant. Anchell claims in "Darkroom Cookbook" that with Stöeckler "is it virtually impossible to overdevelop and takes an effort to underdevelop". The alleged reason being that no development takes place i bath A and bath activates the developer carried over from bath A in the emulsion (the theory behind both its compensating effect and it's forgiving nature wrt. time/temperature). James M. Kates describes in his article on www.largeformatphotography.info/twobath how he actually can change contrast with time in bath A, because contrary to what Anchell says there is a certain development going on in bath A.

Now, Ole Tjugen pointed out for me that Stöeckler bath A and the traditional single-bath D-23 are virtually identical (it is 7.5 grams metol in D-23, whilst 5 grams in Stöeckler bath A), and many seem to forget this fact.

My point is: All sources I have seen point to the forgiving nature of Stöeckler with respect to time and temperature. Virtually all films can be developed in 4-5 mins in each bath. Thornton used a Stöckler variant that he modified for sharpness, but says the same thing about time/temperature. Anchell underlines this property further. How could Thornton control development with this two-bath to achieve "overexpose and 30% underdevelopment"? How come that D23 as a single bath developer is identical to bath A of Stöeckler - why does it develop as D23, but not as bath A in Stöeckler? What actually then takes place in bath B?
Is it so that if one uses single-bath D-23, one needs much longer development time than those 4-5 mins in Stöeckler bath A, and that it is a relativley short development time in bath A that requires the use of bath B. (I.e. given time enough one could develop completely in bath A)? If this is so, it points back to my original problem: How did Thornton control development in his two-bath developer?

I think the point of the two bath is that you don't control development beyond dilution - highlights are automatically held back once the developer is used up. His comments about overdevelopment were in relation to one shot developers where time is a controlling factor. Not sure what film speed (shadow detail) issues would be with 2 bath.

Thornton advocated using a developer like Perceptol or Microdol X highly diluted using the principles you describe. He, being a roll film user primarily, was looking for a way to have almost "automatic" development which would allow each frame to develop to completion. A 2 bath allowed him to do that because once the developer is exhausted, it will theoretically not allow overdevelopment. Highlights would be exhausted, while shadows would keep developing for a while.

So, Thornton was telling those of us who use time and temperature development to be careful, don't blindly follow the instructions on the box. For himself, he followed his own warnings with time and temperature development, or he used his 2 bath as an automatic compensating developer. He tried to develop his Dixactol as a two bath, but found out that it worked better as a single bath with semi-stand development.

Thornton also used varying amounts of accelerator in his B baths to achieve a measure of control not usually considered by people using two baths. I think he used 8g/L of sodium metaborate for N-1, 12g/L for N, and 20g/L for N+1 development.

n his old website (now at www.barrythornton.com) Thornton said "Actually little development takes place" in the first bath, so he was aware that there was some development taking place. Remember also that Thornton changed the Stoeckler formula in several ways. One of them was to drop the sodium sulfite in the A bath from 100g/L in the Stoeckler formula to 80g/L in his. Perhaps this reduced the amount of development that takes place in the A bath to a negligible amount. I I have not tried it, but I suppose we could test this by developing the film in the A bath for 4-5 minutes and then fixing it.

I use his two bath also. I have not worried about temperature at all. I find that this formula gives me excellent negatives even in high contrast situations. I have also tried splitting the Sodium Sulfite so that each bath contains 40g/L. I suppose that this reduces development in the A bath even further, perhaps even eliminating it. Results were fine, as far as I was concerned.

Stockler 2 bath

I have recently swithed my developer of choice to a variant of Thortants' variant. I add a little sodium bisulfite to bath a which brings the ph down to @ 7.2. At that level no development takes place in bath a. I control the contrast in bath b by varing the ph. Normal contrast at ph 10.5. Low contrast at ph 9.5 - 10. Higher contrast at ph 11 - 11.75 It does not seem to matter the film or the speed, they all come out just right at 5 min in each bath. Constant slow aggitation in bath a and no aggitation in b. I have been very impressed. Cheap too. In straight D-23, yes some development does take place but it is very very slow and very soft.

Thanks for all the feedback. This is really helpful in understanding how these developers actually work. I realize that on rollfilm, it is not as easy with contrast control during development as for sheet film, and it is this very challenge that the two-bath developers try to address. What I am aiming at is to identify the N development time for a given film and EI. I have made some tests on various films with Thornton's variant, and they all gave slightly different highlight densities (by slightly I mean +- 1 zone), and I would like to know which parameters to manipulate to place the curves where they should be for the highlight zones.

Are you saying you get different results (+ or - one zone) with different films? If yes, it seems to me that this is comparing apples to oranges. Different films may have emulsions that are formulated to render the highlights differently. Similarly, different films are likely to react differently to a given developer.

An alternate approach would be to experiment with one film, and vary time or temperature (not both at once) to see if there is a difference in the highlights using Thornton's formula. If yes, you can then adjust development times or temperature to get the results you want based on your tests.

Alternatively, if you are satisfied that you do not see much change in one film based on differences in time and temperature, then you can try varying the concentration of accelerator in the B bath to see how that impacts the highlights.

anyhuus said:

... snip...I realize that on rollfilm, it is not as easy with contrast control during development as for sheet film, and it is this very challenge that the two-bath developers try to address. .... snip....

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No. Contrast control on rollfilm is exactly the same as on sheet film.

2 bath developers induce a shoulder, reducing the proportion of density gained to the amount of exposure, in the highlight region of the film.

Some films, with single bath developers, do this by nature. Xtol and TMX for example.

Many photographers use a film + developer combination that induces a super proportionate density increase. The curve has an upswept curve. An example would be HC-110 and almost every film. No combination of exposure and development can change this.

Neither combination is perfect for every type of scene.

That is why we use papers of different grades.

Two bath developers simplify and complicate matters. In the end, it is a zero sum: they are no better, nor worse... just different.

Some film and developer combinations are exactly proportionate in their highlight response. An example is FP4 and Aculux 2, or XTOL.

As there is no compression in the highlights, fidelity is automatic. In many cases, Normal development is correct regardless of the scale of the scene, as it can be printed easily with different grades or filtration.

Now, the 2 solution baths Thornton worked with may induce acutance effects which may be desirable. Single baths, as well, can do the same, usually with more control. Since 2 bath developers require varying times and concentrations to compensate for a specific films respone, it is no different to using a single bath developer which requires a different time for different films.

While many of Thornton's insights were keen, consider that there are alternatives, many of which are equally useful; some are more straightforward.

You might look at the recent Steve Sherman thread regarding semi stand development, a process Geoffrey Crawley has advocated since the '60s.

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Going back to the beginning, I should mention that it is useful to conduct film speed tests with Thornton's 2 Bath, and it is much easier to do this than with single baths.

Here is how I do it, others may differ. Find an area of open shade with a variety of shades or zones in it, inlcuding shadows where you would want to see zone 3 detail. I try to find an area that includes some highlights. Since I use 4x5, I test by exposing 4-5 sheets at, above, and below the manufacturer's film speed. For example, with HP5+ I exposed sheets at EIs of 100, 200, 400, and 800. Include a note with the EI in each photo. Develop the film. Thornton recommended 5 minutes for sheet film, and that is the time I use. Examine the exposures for good shadow detail. Highlights should be fine, due to the compensating nature of the 2 bath. Pick the exposure with the shadow detail you lick.

You can easily do this with roll film by changing film speed with each frame.

davekarp said:

Going back to the beginning, I should mention that it is useful to conduct film speed tests with Thornton's 2 Bath, and it is much easier to do this than with single baths.

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This is exactly what I am trying to do. Well, I am really trying to find both EI and N development time for a number of films in this particular developer.
I have tested 400TX, Delta 400 and HP5+, and look at where the curves crosses the negative density level of speedpoint density + log 1.20. As far as I have understood, this should be 7 stops (or zones) above speedpoint. Then I see that 400TX reaches this density at 6 stops above speed point, HP5+ reaches the highlight density at 6 1/3 stops above, and Delta 400 reaches the highlight density at 7 2/3 stops above.
I have used same time and temp. for all films (5 min bath A, 3 mins bath B @ 20 centigrades). To me this seems that I have found close to N+1
development for HP5+ and 400TX, and close to N-1 for Delta-400.

My aim was (and still is) to find N dev for all these films by adjusting some - until recently - unknown factor. Based on the valuable input from this thread, I will now try to adjust time in bath A, and then try different alkality in bath B.

Again, I am really grateful for all the feedback

2 Bath Developers and D-23

Some of the commentsa here as to no developement taking place in the first bath are contrary to my understanding of the process especially concerning D-23. There is an excellent article in the "Large Format Photography Forum" archive concerning stoeckler 2 bath developer.
The stoeckler formula calls for 5 grams metol whereas D-23 uses 7.5 otherwise the two are virtually the same. With standard amounts of sodium sulfite as called for in the formula's developement does take place in the first bath. I have used standard D-23 with tri-x in straight D-23 and my N times are around 6 minutes. The short(3min) times published for divided developement seems to me are what gives the compensating effect for the highlights while the alkali bath serves to further build the shadows.

A quick comment from a complete amateur here ... I use D-D23 almost exclusively. I find that changing the length of time in the D23 is what gives me the greatest control over level of development. The time in the Borax does't seem as critical to me unless the time in "A" is much shortened - maybe because the second bath is a "to completion" bath?