[pure-silver] Re: Adding Pot Bromife to PC-TEA
- From: "Koch, Gerald" <gkoch02@xxxxxxxxxx>
- To: "'pure-silver@xxxxxxxxxxxxx'" <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 6 Jan 2005 16:49:46 -0500
I worried about this too. The solution does darken but still works.
I have found that you don't have to heat the solvent as hot as Gainer suggests.
I put the TEA or glycol in a beaker and add the ascorbic acid. I start heating
the contents in the microwave in 10-15 sec intervals. I stir the solution after
each heating to see if all the solid will dissolve. When it finally does I then
add the Phenidone or Dimezone-S. This way the solution does not get overheated.
The bromide is another matter since it is an ionic solid and should not be
soluble in non-ionic solvents. In fact I did not consider its use it until I
read that someone else was adding a small amount to the concentrate. About a
quarter of a gram will dissolve with some difficulty in 100 ml of pure TEA or
1:1 TEA/glycol. Best to grind the potassium bromide to a powder first. Back in
the days of wet plates they used lithium bromide because it was soluble in
ether. This chemical is hard to get but ammonium bromide is also soluble in
ether. In light of this, I suspect that it would be more easily soluble than
the potassium bromide.
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx]
On Behalf Of John Black
Sent: Thursday, January 06, 2005 3:28 PM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: Adding Pot Bromife to PC-TEA
> 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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