[pure-silver] Re: Fishy developer: NOW Triethanolamine
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: "'pure-silver@xxxxxxxxxxxxx'" <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 17 Dec 2004 14:32:14 -0500
One doesn't have to use straight TEA as the solvent in the Gainer formula. The
solvent could be and mixture of TEA and propylene glycol or something similar.
This would drop the pH of the concentrate and also the working solution.
Jerry
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx]
On Behalf Of John Black
Sent: Friday, December 17, 2004 2:05 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Fishy developer: NOW Triethanolamine
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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