Re: oil prints

----- Original Message -----
From: "Witho Worms" <info@witho.nl>
To: <alt-photo-process-l@usask.ca>
Sent: Wednesday, May 24, 2006 5:58 AM
Subject: RE: oil prints

I will try plain hypo first and then bark at the dogs, if
nescessary.

Regards,

Witho

  _____

Van: Loris Medici [mailto:mail@loris.medici.name]
Verzonden: woensdag 24 mei 2006 14:43
Aan: alt-photo-process-l@usask.ca
Onderwerp: RE: oil prints

   Kodak F-24 is a non hardening acid fixing bath. It is
less acid than hardening baths but still acid. Hypo does not
need to be acid to work. The acid is needed by alum
hardeners and is also used to prevent carried over developer
from becoming re-activated.
   Where only fixing is needed one requires only hypo and
some sodium sulfite. The purpose of the sulfit is to protect
the hypo from oxidation. Much less sulfite is needed in a
non acid bath than in a regular acid fixing bath. Most acid
fixing baths contain about 15 grams per liter of Sulfite,
For a plain bath about 5 grams per liter is enough. Sulfite
is very slightly alkaline. A typical "plain" hypo bath would
be:

Sodium Thiosulfate, crystaline 240 grams
Sodium Sulfite, dessicated 5 grams
Water to make 1
liter

    This bath is the same strength as standard fixing baths
for conventional B&W processing. For some processes, such as
printing out paper, this is too strong and can be diluted to
whatever strength is desired.

     If you are using Sulfite as a wash aid it should
probably not be contained in the same bath as the fixer but
I am not at all sure of the chemistry here. Kodak Hypo
Clearing Agent at working strength contains about 20 grams
per liter of Sodium Sulfite along with enough Sodium
bisulfite to result in neutral pH and two sequestering
agents, EDTA Tetra sodium salt, and Sodium Citrate. The
purpose of the buffering is to minimise emulsion swelling.
The purpose of the two sequestering agents is to prevent
deposition of alum from hardening fixing baths and
carbonates from the water onto the film or paper. Sodium
sulfite by itself at about 2% works nearly as well as the
more complicated formula.
    I suspect Ryuji Suzuki could clarify whether the sulfite
in a plain fixing bath has the same effect as a subsequent
wash aid bath, assuming its there in sufficient
concentration.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com