Question for the chemists

David Allen said:

I have been using Barry Thornton's Two-Bath developer for more than a decade.

1 litre was always good for at least 15 films and kept for at least 6 months.

I have always used a pre-soak so that Bath A does not become full of the dye.

Recently, both myself and a former pupil have been experiencing Bath A turning a mid grey colour after only 4 - 5 films and after only a couple of months.

So, finally to my question, the only thing that has changed is that both our recent batches of Metol were not white but a light tan colour. Could this be the cause of the problem?

Many thanks for your help,

David.

There are so many variables presented by your question that I do not think a reasonable answer can be made. In the end, the problem, if any, is whether you are getting the images you want. The color of the developer, if fresh, is probably irrelevant.

However, what is relevant is that you are misusing the developer. By the way it works (chemically), you do not pre-wash the film prior to development. This developer depends on the film emulsion absorbing a quantity of the first part of the developer, then going to the second part of the developer without any intervening wash. If you "pre-wash", you load the emulsion with water, which inhibits the intended infusion of the first developer.

Click to expand...

David Allen said:

Yes I talked to several other photographers here in Germany who make their own developer and all had experienced the same problems with dramatically reduced capacity from the light tan coloured Metol from the same supplier. All said that it worked fine at first but then quickly discoloured to a point where they did not want to use it for fear of ruining their films.

One of the people I talked to was Wolfgang Moersch (https://www.moersch-photochemie.de/content/news) who makes and sells a wide range of interesting products. He had tried the discoloured developer and found that "the only directly visible disadvantage is the grey colour of the solution and a dark, uncomfortable precipitation at the bottom of the bottle. Such solutions are still effective, but I cannot guarantee that exactly the same densities will occur during film development" and this pretty much mirrored my own experience.

I then sourced some Metol from a supplier in Poland and that was white and the developer worked as expected and retained the capacity for 15 films and only had the expected slight discolouration by the last batch of films.

I then contacted my usually reliable and competitively priced chemical supplier (Fototechnik Suvatlar in Hamburg whose price list you can see here: http://moersch-photochemie.de/moersch/webroot/files/Preisliste_online_2018final.pdf) and they agreed that the light tan Metol was substandard and confirmed that they had, after I had purchased my last 50g of Metol, changed to another source.

They then supplied me with new Metol for free and this was white in colour as normal. Subsequently, my former pupil also contacted them and they also supplied him with new Metol free of charge. So heads up to Fototechnik Suvatlar for very good customer service.

Currently, my latest batch of Barry Thornton's Two-Bath has now been used for 8 rolls and remains, after nearly two months, pretty clear with only the usual slight change in colour.

Bests,

David.
www.dsallen.de

Click to expand...