[pure-silver] Re: Sodium bisulfite
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Thu, 10 Mar 2005 23:32:27 -0800
----- Original Message -----
From: "Fyodor M. Tcheredeyev" <fyodor@xxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, March 10, 2005 2:46 PM
Subject: [pure-silver] Sodium bisulfite
> Dear all,
>
> David Vestal in "Advanced B&W Printing" gives the
> following solution
> for washing aid for paper:
> water 3 liters
> sodum sulfite 80 g
> water to make 4 liters
>
> Which so far is all right, then another one for film:
>
> water 3 liters
> sodium silfite 80 g
> SODIUM BISULFITE 8 g
> water to make 4 liters
>
> Today I went to the local chemistry shop, and was told
> that they have
> SODIUM BISULFITE (NaHSO3) as a 37% solution. It's also at
> least 10
> times more expensive than sodium sulfite.
>
> The questions are:
> a) is the NaHSO3 the right sodium bisulfite, the one
> needed for the
> wash aid, and if yes
> b) how do I come to a 8 g equivalent of a 37% solution?
>
> Thank you very much in advance.
>
> Also some (rather long) time ago someone on the list (I
> think it must
> have been Richard Knoppow, but I may be wrong, quoted
> another wash
> aid, that included a third element, a salt something
> something. Is it
> at all possible to get that recipe, please - I lost all my
> records due
> to both a move to another place and a computer upgrade...
>
> Thank you very much in advance.
>
> --
> Best regards,
> Fyodor mailto:fyodor@xxxxxxxxxxxx
>
>
I think I am getting messages out of order and that
Ryuji Suzuki may have already responded to this. The formula
I posted is a guess as to the formula for Kodak Hypo
Clearing Agent. I think it is reasonably accurate.
Wash Aid Stock Solution
Water, at about 90F 750.0 ml
Sodium Sulfite 100.0 grams
Sodium Bisulfite 20.0 grams
EDTA tetra sodium salt 5.0 grams
Sodium Citrate 5.0 grams
Water to make 1.0 liter
The solution should have a pH of 7.0
For use dilute 1 part stock to 4 parts water. Treat film and
single weight paper for 1 to 2 minutes. Treat double or
premium weight paper for 3 minutes.
The paper on this solution shows that is has its maximum
effect at 4 minutes and longer soaks do not serve much
purpose.
Kodak gives after treatment wash times as:
Film, 5 minutes
Single weight paper, 10 minutes
Double weight paper, 20 minutes
While sodium sulfite by itself makes a good wash aid the
buffering to neutral pH has two desirable effects: 1, it
minimises emulsion swelling which according to the Kodak
paper results in the shortest diffusion path for the hypo to
take in leaving the emulsion; 2, it is a pH at which the
mordanding effect of alum hardener is eliminated but the
hardening is not undone.
The two other ingredients are chealating agents. While
these may not be necessary for the wash aid if it isn't to
be reused they may also have some benificial effect on
washing so I would add them if available.
Long ago there was a discussion of what exactly was meant
by sodium bisulfite in Kodak and other formulas. It appears
that the compound is actually metabisulfite, or mostly so.
Sodium metabisulfite is much less expensive than real sodium
sulfite and is certainly suitable for this formula.
Its useful to have formulas for things you need in case
the commercial product becomes unavailable but I don't know
that its any cheaper to make this stuff from scratch as long
as it does come packaged.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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