For your information, the levels of Sodium Metaborate suggested by Thornton are:
N+1 = 20g
N = 12g
N-1 + 7g
However, I am very surprised that you have got blown out highlights. I have used BTTB developer for many years as my only film developer and have never had this problem. I am very often shooting images that have extremely bright contrast ranges and it has never been a problem for me. Indeed, all of the images on my website are with Delta 400 rated at 200 and developed for 5 minutes in each bath. All my negatives print straight on Grade 3 using a Multigrade 500 diffusion head. However, I frequently print on a harder grade to get the particular look that I like but, even this only requires a couple of seconds burning in the very brightest highlights (hence my confusion that you are getting blown out highlights).
In this first example photograph I metered the shadow at the bottom of the chimney and placed it on Zone III - the white etched wall read ten zones more but there is detail throughout:
View attachment 89801
In this second photograph I metered the base of the tree to the centre right and placed it on Zone III - the area surrounding the street light was completely off the scale. Nevertheless, and although it might not show in this scan, there is tonality throughout except for the actual street light itself:
View attachment 89802
If you are having problems, I would suggest you look at the following areas:
Developer temperature
Frequency of agitation
Time
People regularly state that time, temperature and agitation is not critical with two-bath developers. This is plain WRONG. Two-bath developers should be treated with just the same care and attention to detail as any other developer. I have also read frequently that one should use stand development with the second bath when using two-bath developers. I tried this once and got negatives with uneven development - so never again.
Over vigorous development, as with most developers, may cause problems but, in my experience, the usual cause of problems is not taking care to ensure that every stage of the development process is constant from film to film. This really is the key to development irrespective of your choice of developer.
Perhaps the most useful information, is for me to outline my processing sequence and then you might be able to identify where your way of working is very different from mine.
Firstly, I do not use metal tanks - so this should be taken into consideration.
The processing sequence that works for me (using Paterson plastic tanks and ALL chemicals always at 20C) is as follows:
00:00 pre-soak with constant agitation
01:45 drain pre-soak out of the tank
02:00 Pour Bath A in and gently invert 4 times in the first 30 seconds followed by a sharp tap on the bottom of the tank to dislodge any possible air bubbles. Then one gentle inversion every 30 seconds always followed by a sharp tap on the bottom of the tank to dislodge any possible air bubbles.
06:45 Pour Bath A out of tank into a jug.
07:00 Pour Bath B in and invert 4 times in the first 30 seconds followed by a sharp tap on the bottom of the tank to dislodge any possible air bubbles. Then one gentle inversion every 30 seconds always followed by a sharp tap on the bottom of the tank to dislodge any possible air bubbles.
11:45 Pour Bath B out of tank into a jug.
12:00 Pour in water stop bath and agitate constantly
12:45 Pour water stop bath out into the drain.
13:00 Pour in fix and agitate constantly
15:00 Remove films from tank and place into a large jug of water and leave until all of the pink dye is removed from the film then return the film to the fix for a further 2 minutes.
Finally, wash using the Ilford method.
A note on mixing the chemicals and use
◦ I mix up 1 litre of Bath A (my tank is the 1 litre version that can accommodate up to 4 films) and store in a 1 litre dark brown glass bottle. This one litre is sufficient for 24 films (but note the following point about Bath B).
◦ I mix up two litres of Bath B at the normal 12g of Sodium Metaborate (which are stored in two 1 litre dark brown glass bottles) and use each bottle of Bath B for 12 films and then discard.
◦ I mix up one litre of Bath B at the N+ dilution of 20g of Sodium Metaborate (which is stored in a 1 litre dark brown glass bottles) and use rarely when needed.
A note on the N-, N and N+ dilutions
◦ 99% of all my photographs are developed with the N version of Bath B. I have never had any negative where I felt that it should have been developed using the N- version of Bath B.
◦ The N+ version of Bath B is useful but not in the sense of a strict +1 stop expansion (which can be much better achieved by selenium toning the negative). If I photograph something that has dark shadows and bright highlights but also a significant part of the scene is relatively lacking in mid-tone separation then I use the N+ version of Bath B. This has a significant effect on expanding the mid-tones of a scene that was lacking such a mid-tone separation.
Having just quickly looked through the 100 odd images on my website, there are 6 photographs where I used the N+ Bath B and all of the rest were developed using the normal Bath B.
Best of luck finding your own best way of using Thornton's two-bath developer - it is a great, reliable and cheap developer.
Best,
David
www.dsallen.de