The history of two bath developers | Pictorial Planet Blog

The history of two bath developers

In the early days of photography, people developed their pictures from single plates but most of us don't have that ability. We develop multiple negatives at a time from our roll films. And this is why two bath developers were created …

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The history of two bath developers



I’ve always been interested in the more unusual developing techniques. Techniques like monobath, development by inspection, and two bath developers. They all have their place and I believe that one should, at least, take a look at them as one’s skills grow in the darkroom. One of these that I do use a lot is Two Bath development, sometimes called Divided Development (although, arguably Divided is slightly different but, for the sake of this blog, I’ll use the words interchangeably). Today I want to take a look at the history os such a technique.

In the early days of photography, people developed their photographs from single plates. These were glass plates that fitted in the back of the (large format) camera and allowed the taking of a single shot. The plate was then carefully removed and another fitted. That plate would become a glass negative. Nowadays, most of us don't have single plate negatives to work with, we have multiple negatives all together on a single roll and this is why two bath developers were invented …

In the beginning



Photographic plates, as single negatives, allowed each to be developed individually. The plate is developed in a tray and given the exact development time needed according to the contrast range of the shot. If the photographer bracketed shots using several plates or took several shots at the same exposure, he or she could alter development for each using a trial and error system or by inspection. Therefore, when using these early plates or separate negatives it was easier to get the the development time exact for that photograph. But nowadays we have the problem that all our negatives, regardless of exposure and contrast range, are all on the same roll. Our roll comprises of many different negatives, each potentially needing a different development time to keep their contrast range within that of the film/paper or to be expanded to give flat scenes a full range of tones.

Heinrich Stoëckler may have been the first




Heinrich Stoëckler was a photographer who lived to see roll film become ubiquitous. He cleverly came up with the solution of how to develop each negative on the roll separately. He used the two bath concept when formulating his famous developer just before World War II. This type of developer is so effective that it is still relatively popular today - Diafine, although not based on Stoeckler’s formula, is a popular two bath in the U.S..

The Stoëckler Formula Two Bath



Bath A:


Metol 5g
Sodium Sulphite 100g
Water to make 1ltr

Bath B:


Borax 10g
Water to make 1ltr

- Try four minutes in each bath at about 20c

With a two bath developer like this you can rely upon it to develop each negative on the film individually therefore giving you the best of both worlds - roll film practicality and individual development.

Another useful attribute



Two bath developers also have another useful attribute. They can develop different films of differing ISOs together for the same length of time. This means that you could develop your roll of Tri- X at the same time as your roll of FP4+. The two films will be correctly developed together in the tank for the same developing time.

Ansel Adams promoted the use of a two bath for contrast contraction. He worked with large format plates and the Divided D-23 formula which is, by the way, very rooted in the Stoekler formula. However, for me it’s the frame by frame compensation on roll film that makes two bath development so useful today.

How they work



Two bath developers are compensating developers. They utilise the exhaustion of the developing agent and stop processing the highlights when they are ready. Barry Thornton’s formula is the most up to date and is specifically formulated to give very good results with modern film emulsions. Thorton’s formula shows improved sharpness over the others by lowering the amount of Sulphite and consequently lessoning the re-plating of the silver and therefore the softening of negative sharpness through . You can process 15 rolls of film through his two bath - which is somewhat more than the Stoëckler and Adams D-23 variants.
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