[pure-silver] Re: Fishy developer: NOW Triethanolamine
- From: "John Black" <jblack@xxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 17 Dec 2004 14:05:21 -0500
Ryuji sayeth:
>
> > One manufacturer had the following table which may be useful.
>
> Actually this type of table is not useful at least for photographic
> purposes because diluted pure TEA is rarely (if ever) used. When you
> mix one with other chemicals the pH of the mixture is a result of
> complicated interactions of all constituents.
> --
Indeed TEA needs the presence of a mild acid to form an effective buffer,
usually between pH of 8 and 10. Boric acid works quite well (as in DS-10).
Patrick Gainer, however, uses it mostly as an accelerator in his formulas
for PC-TEA where he heats TEA to 250F and disolves penidone and ascorbic
acid in it. This mixture is then diluted with water to make developer. The
pH is rather high for my tastes, though, at 9.0. Water with a few grams of
boric acid may be used as diluent though to yield a useful developer.
Gainer's persistant aversion to sulfite puzzles me as the simple addition of
a small amount of sodium sulfite to the PC-TEA substantially increases its
activity.
JB
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