Interesting work. Thank you for the effort and for sharing the results.
I am curious about the concoction with 10x borax. Why would this result in increased contrast? I would not have expected this. Does the pH increase that much with the additional Borax? I would have thought (I am no chemist) that after a point additional Borax would have very little effect on pH.
Does the addition of the 20grams of Boric acid bring the initial pH back to around 9.25?
I have many questions about the purification process too...but...it seems completely un-necessary to me? Perhaps to you too? Would the stuff straight from the 20 Mule team box not work just as well?
Perhaps, a direct comparison of the purified to the non-purified is in order? Or, even, between reagent grade and straight 20 Mule Team?
Thanks again for publishing.
I there are two aspects of pH. Two developers may have the same initial pH, but one may have a greater resistance to change of pH. The reaction of silver halide to development produces the halide acid as well as metallic silver. The acid then acts to reduce the local pH of the solution, more where the exposure was greater. The reduction of pH thus reduces the local activity of the developer. That is what we count on in stand or semi-stand development to produce "compensation", allowing density to build up in shadow areas at a somewhat greater relative rate than in the highlights. The initial effect of the boric acid I added was to bring the initial pH to around 8.6, but also to reduce the local dynamic change of pH.
interesting....I cannot pretend to comprehend all of this, but it is very interesting.
I'm unclear about one thing though, if the increased contrast is expected (at least partially) due to the solution's greatly increased buffering capacity, would we not also expect increased contrast in the solution with both borax and boric acid? That is to say, wouldn't the solution with the excess borax and boric acid also have much greater buffering capacity than the nominal...and therefore also exhibit less (localized?) compensating effect?
Clearly, it is complex.