Barry Thornton Two Bath etc

Pictorial Planet

From the author of "The Art of Black and White Developing"

Barry Thornton's Two Bath etc.

Subscribe to our new newsletter!

Stacks Image 16

Here is something for you to think about!

On a roll of 35mm film we get up to 36 individual shots. Each shot might be quite different in contrast to the next. We may have taken all these shots over many days, weeks, or even months. Some of the shots might have only 3 stops of contrast, some 5 stops (now on the limits of the film), and others may be more, with 6 or 7 stops of contrast.

with normal development the highlights of the high contrast shots will burn out - they will become solid white. Of course, we know what to do, we need to reduce the development time, to maintain detail in these highlights right? Ah, but now the normal contrast scenes will look flat and the low contrast scenes will be very flat. These low contrast photographs have now been seriously underdeveloped.

How are we supposed to decide what time to develop our film for? Should we:

1. Process for the low contrast shots, increasing development time, so as to increase contrast? This will over develop the other negatives and burn out their highlights.

2. Process for the normal contrast shots and hope that the flat photographs and the high contrast photographs are printable? This is the usual answer where some negatives are under developed and some over developed. It’s hit and miss whether a negative will be printable.

3. Should we process for the high contrast photographs, reducing our development time and trying to increase contrast for the rest at the printing stage using a high grade of paper? The normal and the flat shots will be under developed and very difficult to print.

Well, why struggle with this predicament. Why not let the developer do all the work for us! Let it decide when to stop processing the highlights and the shadows!

Why not let the developer do all the work for us!
For the history of two baths look at this blog entry

Two bath developers are compensating developers because they utilise the exhaustion of the developing agent and stop processing the highlights when they are complete. Barry Thornton’s formula is the most up to date and was specifically formulated to give very good results with modern film emulsions.

Thornton’s formula is largely based on Divided D-23. However, he didn't want D-23's softness due to the high sulphite level. So he experimented and found the magic level of sulphite was 80g per litre. That, he found, was where the D-23 softness was considerably reduced. Barry Thornton's two bath shows improved sharpness by lowering the amount of Sulphite and consequently reducing the re-plating action of the silver. You can process 15 rolls of film through his two bath - which is somewhat more than the Stoëckler and Adams D-23 variants.

Barry Thornton’s higher definition Two Bath

Bath A
Metol 6.5g*
Sodium Sulphite 80g**
Water to 1 litre

Bath B
Sodium Metaborate 12g
Water to 1 litre

* A later version increased the metol from 6.25g to 6.5
** This same later version lowered the sulphite to 80g

Barry's two bath formula works very well and is a developer I always keep in my darkroom It develops different ISO films together without problem, is sharp and compensating. It's a developer I recommend to people that are not sure what they need or want.

Using a Two Bath developer

All two bath developers are used in a similar way:

• Do not pre-wet the film with two bath developers.
• Pour in Bath A and rap the tank to dislodge any bubbles sticking to the film.
Agitate gently for the first 30 seconds to one minute to completely soak the emulsion.
• Agitate for 10 seconds each minute. It’s not too important as only slow development takes place in Bath A. We agitate to avoid streaking and to ensure that the developer saturates the gelatine evenly.

After bath A, pour off the liquid and save it for future films. It can be reused many times with no effect on quality. See the developer instructions for its approximate capacity.

Note: Do not rinse or stop the film between baths.

• Now, pour in bath B. In bath B the development really gets going as the bath is composed of the accelerator. Once the liquid has been poured in we agitate for 5 seconds and rap the tank to dislodge air that might stick to the emulsion.

• Agitate gently for 5 seconds every minute. Then pour bath B out and save it too. Bath B can be re-used also. Each developer formula states how many times.

• Stop and fix as usual.

For all 2 baths, stop and fix after bath B in the usual way. The film goes from the first to the second bath without washing.

Thornton's two bath works very well at around 5 mins in A and 5 mins in B. Use that as a starting point.

All content copyright © John Finch 2018 All Rights Reserved. All Trademarks acknowledged. E&OE Contact Me