[pure-silver] Re: Adding Pot Bromife to PC-TEA
- From: "John Black" <jblack@xxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 6 Jan 2005 15:27:57 -0500
> When you say it is grainier than than you would like to what film are you
> refering? 5231 has the same RMS granularity as Plus-X. I find the grain
with
> this developer so fine that I have difficulty using a grain focuser.
My research film is the new Tri-X emulsion in 35mm. I also use Neopan 1600,
so grain can be an issue. The fine grain films are not nearly as sensitive
to developer conitions as are these two.
>
> You say disperse rather than dissolved? The ascorbic acid and Phenidone
are both soluble in TEA.
I mean disolve in the context of water solution where ionization takes
place. Neither component is ionized in these solvents.
You will have to heat the TEA to make them dissolve but
> you will get a clear solution.
This is true, but much heat is required (250F) and I am nervous about heat
with developing chemicals. I realize that the activity seems to be entirely
intact after heating to this temperature, but I try to avoid it if I can.
>
> Using propylene glycol really cuts the viscosity of the TEA way down. My
experience with methanol is that Phenidone doesn't keep very well in it.
That is quite true if the phenidone is alone in solution. If you disolve
the ascorbic acid in the methanol first, the phenidone is protected much in
the same way reactants need a little sulfite for protection in water
solution.
I'll admit that I haven't tried ethylene or propylene glycol yet as solvent
because of the heat needed but I have some and will try it if my methanol PC
solutions prove unstable. So far, solutions containing 10gm ascorbic acid
and 250mg phenidone per 120ml methanol hold their activity fine for at least
5 months. We'll see about longer. BTW, the PC solution is diluted about
1:40 in pH 8.3 buffer for use (final concentration of about 50mg/L phenidone
and 2gm/L ascorbic acid. This gives CI of 0.50-0.55 on Tri-X and N1600 when
used for 13.5min @ 20C.
JB
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