Thornton 2 baths developer
I am about to test the 'Thornton 2 baths' formula.
I will develop 35mm FP4+ and HP5+ films for a condenser enlarger in a paterson tank.
For those who do not know it, see :
Can you share your experience on :
- processing time/temp/agitation
- which films you use
- results speed/grain/acutance
- contrast control
- any changes to the original formula... ?
Thank you !
Marc, Thornton revised his published formula and included it in his book "The Edge of Darkness." He increased the metol to 6.5g/L. I am going from memory, but I think he reduced the sodium sulfite in the A bath to 80g/L. I e-mailed Mr. Thornton before his death, and he confirmed that the formula in his book was more current than the one on his website. I have used it with good results as refined in his book, plus I have made one change from time to time. I have used it with 40g/L sodium sulfite in Bath A and 40g/L in bath B. This works, and does not seem to be materially different than the results I receive when putting all of the sodium sulfite in Bath A.
I have used this formula with FP4+, HP5+, Fortepan 400 (Arista.Edu 400), and Delta 100 in 4x5, and HP5+ in 120. IEs are 64-80 with F54+, 200 with HP5+ and Fortepan 400, 50 with Delta 100. Temperature varies from approximately 68-75 degrees F. I process 4x5 for 5 minutes in each bath, 120 for 4 minutes in each bath. I think Thornton recommeded these times at 70 degrees F, but I have seen little if any difference in the temperature range I have used.
For contrast control, I have followed Thornton's suggestion of 12g/L of sodium metaborate in bath B for N, and 20g/L in bath B for N+1 development. I have not had to try N-1 development due to the automatic compensating nature of this 2 bath, but Thornton recommended trying 8g/L in bath B for an N-1 effect.
I like the results very much, but have not yet tried it with 35mm film. Others often state that the 2 bath developers are inadequate in comparison to modern single bath developers used with modern films. I have not seen the problem using this formula.
Davekarp, I have read 'Edge of Darkness', and I confirm his modified formula :
Bath A water 750 ml / Metol 6.5 g / Sodium sulfite 80 g / Water to 1 L
Bath B Water 750 ml / Sodium metaborate 12 g / Water to 1 L
What is the idea behind splitting the 80 g sodium sulfite beteween bath A and bath B ?
I split the sodium sulfite between the two baths due Anchell's and Troop's comment that staining, streaking, and/or film swelling are potential problems when using a plain alkali B bath. They suggest adding 50g/L of sodium sulfite to the B Bath to avoid these problems. In addition, they discuss Vestal's divided D-76, in which he divided the sodium sulfite 50/50 in the two baths. I sort of combined the ideas, and split the sodium sulfite between the two baths.
I suppose that I could have split the sodium sulfite 30/50 in the two baths, but the 40/40 split seemed to work fine so I never tried it. Later, I mixed the two baths as Thornton recommended, and never had a problem with streaking, staining, or swelling. I did not see any real difference in results, so I have not used my variation for a while now.
With respect to two-bath developers of this type it's more than worth while to read http://www.largeformatphotography.info/twobath/ which, instead of repeating the traditional conception actually did test how to achieve N, N-, N+ and came to some very surprising conclusions.
Having used and testet the Stoeckler formula as well as Thorntons recipe back and forth I can I tell you from my own experience that you will get a decent picture even if you skip bath B alltogether. All you loose is a bit of speed whereas contrast doesn't change by a margin worth mentioning. Ups, that's in contradiction to what you find in the literature about two bath developers including Anchell/Troop, Adams and Thornton, right? Well, if you wan't to know how things work: As I said, the article above is worth reading and provides reproducible, real world test results instead of broad generalizations about two baths.
With the Thornton formula I found 3.5 mins at 20 °C/68 °F to be a good starting point for Agfa APX as well as Fuji Neopan 400 and Kodak Tri-X new. Speed is about 1/3 to 1/2 stop lower than ISO-speed.
Grain is low, accutance adequate (I take Pyrocat for if I want sharp edges), Contrast control is ok (did I say you should read the article?).
I liked to use the formula for its ease of use, tolerant behaviour and relatively good speed. You can have a soft negative and not loose the shaddows which is great if you need it. But contrast is lowered a bit more in the low zones relative to the highlights which makes the shaddows less crisp. Good process control and a standard-developer can give you about the same result with slightly less speed but a more linear curve.
Last edited by skahde; 04-12-2006 at 05:16 AM. Click to view previous post history.
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Can you compare acutance and grain size between the two methods (standard vs modified baths) ?
Thornton describes a contrast control method, modifying concentration in bath B :
Bath B N- Water 750 ml / Sodium metaborate 7 g / Water to 1 L
Bath B N+ Water 750 ml / Sodium metaborate 20 g / Water to 1 L
Thank you for the link. So, Kates describes another approach to contrast control for Stoeckler's 2 baths, based on time in bath A.
If Thornton's formula behaves the same way as Stoeckler's (it should as they are very close), we have 2 methods for contrast control :
- time in bath A
- concentration in bath B
That's quite interesting !
Has anyone already compared ?
Three and likely more. #3; presoak in B then into
Originally Posted by Marc .
A then back to B. One-shot usage.
A starting point could be: A bath, 1 gram metol and 5 of
sulfite; B bath, 5 grams of sulfite or borax or bicarbonate
or carbonate or a blend of two or three of those. All 1
liter. I've not any metaborate so will not mention it.
As was suggested development is usually well under way
in the A bath by times up. S. sulfite is a medium strength
alkali. Anchell, in some of his formulas, includes bisulfite
which reduces the ph. A baths are usually very
D-23 in character. Dan
I have beenusing Barry's formula (version) for years - as published in Edge of Darkness. Works great. Compensating - a little soft. Not gritty like high definition developers. 3 to 4 minutes in each bath - no worries on temp - don't wash between baths. Shelf life is better than 2 years. Better than 15 rolls per liter on bath A - Bath B can be replaced that often or so, it is the one that takes the beating.
My photos are always without all that distracting color ...
Is your #3 method is for N- ?
Can you describe the results ?
Did you try the N+ and N- baths B decribed by Thornton ?
I have detected no difference in acutance or grain between Thornton's standard formula and my modification.