From: Harald Leban (hleban@telering.at)
Date: 05/16/01-05:16:14 AM Z
The Potassiumoxalate we use correctly is the di-Potassium-oxalate and should
have a pH around 6,5-7,0.
If it is on the acid side the solubility is bad and you cannot reach a 30%
solution - because of the free acid. The second disadvantage is that the
developement speed slows down and most of the sensitizer is washed away from
the paper surface before the image could build up ( because free oxalic
acid works like a clearing bath)
You can adjust the pH with Potassiumhydroxide or Potassiumcarbonate
solutions from the acid side or with Oxalic acid or Sulfuric acid from the
alkaline side.
Harald
-----Ursprüngliche Nachricht-----
Von: "Witho Worms en Jorien van Santen" <verzet13@xs4all.nl>
An: <alt-photo-process-l@skyway.usask.ca>
Gesendet: Mittwoch, 16. Mai 2001 09:09
Betreff: Re: Oxalate Potassium doesn't remain dissolved
> You may check the pH of the oxalate solution. If it is to low you can use
a
> hydroxide (potassium) to bring the pH up to around 5 or 6. This will
> dissolve it better. I had the same experience. Different grades of
> potassiumoxalate can make a big difference (a former Harald Leban tip).
>
> Witho
>
>
> ----- Original Message -----
> From: "Eric Neilsen" <e.neilsen@worldnet.att.net>
> To: <alt-photo-process-l@skyway.usask.ca>
> Sent: Wednesday, May 16, 2001 4:08 AM
> Subject: Re: Oxalate Potassium doesn't remain dissolved
>
>
> > Another vendor may be the answer. Perhaps just make it up from scratch
> > would work best and it is 1/8 the cost. I have made many gallons and
have
> > seen a small amount come back out as a precipitate. Jeffrey first
> > suggestion of decanting would also be a great first step. Unless you
are
> > getting less than very good results, don't worry. 300 to 275 grams of
Pot
> > Ox in a liter should be just fine. I don't think that you'll see any
> > change. It may give you a slightly slower print and a tiny amount of
> extra
> > contrast, but very slight on both accounts.
> >
> >
> >
> > Eric J. Neilsen
> > 4101 Commerce Street, Suite #9
> > Dallas, TX 75226
> > 214-827-8301
> > http://e.neilsen.home.att.net
> > http://www.ericneilsenphotography.com
> > ----- Original Message -----
> > From: "Jeffrey D. Mathias" <jeffrey.d.mathias@worldnet.att.net>
> > To: "alt-photo-process list" <alt-photo-process-l@usask.ca>
> > Sent: Tuesday, May 15, 2001 5:24 AM
> > Subject: Re: Oxalate Potassium doesn't remain dissolved
> >
> >
> > > Philippe Ayral wrote:
> > > > ... I try to know where is the
> > > > problem before making a new batch and having the same problem.
> > >
> > > At this point, I do not know.
> > > Clean everything. Check materials (water and PO), and perhaps even
try
> > > materials from another vendor.
> > >
> > > --
> > > Jeffrey D. Mathias
> > > http://home.att.net/~jeffrey.d.mathias/
> >
> >
>
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