[pure-silver] Re: New Dektol, dark brown
- From: `Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 31 Mar 2021 11:09:22 -0700
Being an occasional asthma sufferer I understand about the
sulfur dioxide very well.
On 3/31/2021 5:21 AM, Claudio Bonavolta wrote:
Yes, fixer formulas are not critical and closer to cooking
recipes than rocket science, so it's pretty easy to play with.
Some, like plain hypo, are very basic ...
I forgot to mention the main reason I switched to
neutral-alkaline fixers: my lungs are pretty sensitive to
sulphur dioxide and removing the acid drastically reduces the
release of that nasty gas.
Regards,
Claudio Bonavolta
www.bonavolta.ch
/31 mars 2021 07:06 `Richard Knoppow <dickburk@xxxxxxxxxxxxx> a
écrit:/
I just posted some variations on Kodak fixers. This is
like a
combination of F-7, rapid fixer and F-24, a non hardening
thiosulfate fixer. I have no doubt it works. F-24 has more
bisulfite in it so is more acid but not as acid as a hardening
bath would be.
On 3/30/2021 1:11 AM, Claudio Bonavolta wrote:
> I too use a formula with sodium thiosulfate +
> ammonium-something. I suspect our formulas must be very
similar
> (derived from Kodak's F-7/F-9) ...
> It has the following advantages:
> - neutral pH (following wash is easier)
> - fast fixer (similar to ammonium thiosulfate fixers)
> - uses only powders so shipment and shelf-life of raw
chemicals
> is not problematic
>
> As it's a neutral fixer, I include a brief wash after the
stop
> bath.
>
> Chemical Quantity Comments
> Water 600ml
> Sodium Thiosulfate 360gr crystalline or
230gr
> anhydrous
> Ammonium Chloride 50gr or 60gr ammonium
sulfate
> Sodium Sulfite 15gr anhydrous
> Sodium metabisulfite 5gr
> Cold water to make 1000ml pH around 7.0
>
> Other chemicals are quick wins:
> Stop bath -> citric acid @ 15gr/l
> Washaid -> sodium sulfite @ 20gr/l (to be dumped at the
end of
> the session)
>
> But paper developers are not difficult either ...
> A short page with some links to resources:
> https://www.bonavolta.ch/hobby/en/photo/fo_chem.htm
>
>
> Regards,
> Claudio Bonavolta
> www.bonavolta.ch
>
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--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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