Barry Thornton’s Two-Bath Developer

Photographica — Jordan on May 27, 2007

In his book Edge of Darkness, the late UK photographer and printer Barry Thornton describes his adaptation of an old Stoeckler two-bath B&W developer formula (presumably from the 1920s or thereabouts). Apart from Edge of Darkness and Thornton’s old website, there are few descriptions of the characteristics of this developer (see this APUG thread for one example).

The composition of this developer is as follows:

Bath A
80 g sodium sulfite
6.5 g metol
Make up to 1 L with water

Bath B
12 g sodium metaborate (Kodalk)
Make up to 1 L with water

Thornton and others recommend something like 4-5 mins in each bath (with no pre-soak and no rinse between the two baths) for 400-speed films. The usual characteristics of two-bath developers (such as Diafine) seem to apply: relative insensitivity to time and temperature, within reasonable limits; reusability (also within limits); and long stock solution life.

With only one developing agent and two other ingredients, it’s hard to get simpler than Thornton’s formula. Chemically, Bath A is pretty close to D23, a metol-only developer formulated by Kodak. One of the characteristics of D23 is its low working pH and high sulfite concentration, both of which combine to give a slow-working, fine-grain developer. D23 is no longer commercially available, but is closely related to Kodak Microdol-X and Ilford Perceptol, two commercial developers with similar characteristics. Developing times in diluted Perceptol are often in the 15-20 minute range at 20C.

What to make of Thornton’s two-bath developer, then? Given that Bath B is simply an alkaline solution, it seems that the working principle is the absorption of the ingredients of a slow-working developer in Bath A with a small amount of image formation, followed by the activation of these agents in Bath B by a sudden increase in pH. As with Diafine, exhaustion of the absorbed developing agents limits highlight density to reasonable levels and means that extensions of the Bath B time beyond a minimum value have little or no effect on the image itself. In fact, Bath A could probably be directly substituted with D23 or Perceptol with comparable results.

I mixed up Thornton’s two-bath developer tonight and souped one roll each of HP5 Plus (120) and Tri-X (35mm). I gave the film 4.5 mins in each bath, near room temperature. Density and shadow detail look good. More details to come.


  1. I really want to try Thornton’s formula but the only metaborate I have is anhydrous (NaBO2). Can it be substituted ?

    Comment by Borysław Paulewicz — August 24, 2007 @ 2:45 pm
  2. […] Rolleiflex and Fuji Neopan 400 black-and-white film, developed in the late Barry Thornton’s two-bath metol developer — a great option for anyone who wants a simple, long-lasting, nearly foolproof […]

    Pingback by Photosensitive » Gordon Productions — December 24, 2007 @ 3:35 pm
  3. Sir, your Thornton’s 2-bath results (and some random written experiences on the web) literally forced me to decide for this formula and i’m glad this happened. In terms of tonality, for me your photos are the subject to reach. thank you.

    Comment by miso — February 5, 2008 @ 2:43 pm
  4. […] quimicos aqui tambien hay recetas curiosas… quizas algo mas serias que la de "cafe" Photosensitive Barry Thornton’s Two-Bath Developer __________________ PhotoBlog […]

  5. Hi !

    I just received the stuff to make Thornton two-baths developer.
    I shoot only HP5+ in 120 format.
    How much time should i let the roll into each bath if i expose my HP5+ at 200 isos ? and at 400isos ?

    Thanks in advance 🙂

    Comment by Lionel — January 6, 2010 @ 9:10 am
  6. Thanks in part to this post, Anchell and Troop’s book, and your photos on Flickr, I have successfully developed several rolls of Fomapan 100 in this two bath to great effect. Dev times for me are around 4 mins in each bath to get full development with this film.


    Comment by Karl — July 24, 2010 @ 12:14 pm
  7. Hello;
    RE: “BLEACH,BLEACH,BLEACH AND MONOBATH” [suggested Michael Grayson Healey]

    Can anyone help me about Barry Thornton’s instruction about bleaching old negatives to reduce excessive highlight densities . I understand the two stages of using 2 process bleach method, but he goes on to stage 3 :use monochrome developer:
    ” Tetenal’s pre-packaged Monotenal, or mix your own. Try Sodium Sulphite 6g; Hydroquinone 3g; Metol 0.125g; Sodium Thiosulphate 40g; Sodium Hydroxide 5 g; Water to 250ml.. It is well worth experimenting with this technique. ”
    Question: I cannot locate any Tetenal prepackaged Monotenal, but in looking at “mix-your-own” I find D-76 matches the ingredients… Can anyone confirm this? Thanks

    Comment by michael headley — December 22, 2010 @ 11:28 am
  8. Michael, the “Monotenal” is a monobath developer (fixes as it develops). The formula you’ve provided is also a monobath developer, pretty far from D76 (the sodium thiosulfate gives it away). Might be best to ask on APUG.

    Comment by Jordan — December 22, 2010 @ 12:39 pm
  9. Hi,

    Would you consider Barry Thornton two bath developer close to the discontinued Cachet AB 55 two bath developer. I like the range of temperatures available from 68 to 85 degrees.

    Comment by Edward — March 24, 2011 @ 6:55 pm
  10. Edward, I’ve never tried that developer, so I have no idea. Can you provide me with a link?

    Comment by Jordan — March 24, 2011 @ 6:56 pm

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