A forgotten formula

Scott Coutts wrote:
Nicholas O. Lindan wrote:
You want something called "Farmer's Reducer". It is a mixture of
Pot. Ferricyanide (pretty-much non-toxic, despite the name)

Unless you accidentally mix it with something acidic in your darkroom...
then you get cyanide gas (:

This has been discussed before. It takes quite a bit to
decompose Potassium Ferricyanide. Note that it does not
decompose to form cyanide in the body which means that
you need something stronger than stomach acid.

Treat all darkroom chemicals with respect. It is good to
read the MSDSs for the various chemicals you use, but it
can help to remember that they tend to be written in a way
which makes any chemical sound scary.

Peter.
--

Peter Irwin wrote:
Scott Coutts wrote:

Nicholas O. Lindan wrote:

You want something called "Farmer's Reducer". It is a mixture of
Pot. Ferricyanide (pretty-much non-toxic, despite the name)

Unless you accidentally mix it with something acidic in your darkroom...
then you get cyanide gas (:


This has been discussed before. It takes quite a bit to
decompose Potassium Ferricyanide. Note that it does not
decompose to form cyanide in the body which means that
you need something stronger than stomach acid.

Treat all darkroom chemicals with respect. It is good to
read the MSDSs for the various chemicals you use, but it
can help to remember that they tend to be written in a way
which makes any chemical sound scary.


Yeah, I agree with all of that... but it's good to know. Sometimes
people dont realise the effects that these can have, though, because
they're "just photography solutions... they cant do any harm". Tip it in
the sink with brick cleaner from the hardware shop, for example, and
it'll be quite different!

The MSDS is a good idea, but I agree that they can sound bad. The MSDS
for water is available at some sites, as is the one for salt etc...
you'd never touch anything again if you took them too seriously (not
that I advocate taking them lightly, but a little knowledge and some
common sense never goes astray!)

Scott.

Peter Irwin wrote:
Scott Coutts wrote:

Nicholas O. Lindan wrote:

You want something called "Farmer's Reducer". It is a mixture of
Pot. Ferricyanide (pretty-much non-toxic, despite the name)

Unless you accidentally mix it with something acidic in your darkroom...
then you get cyanide gas (:


This has been discussed before. It takes quite a bit to
decompose Potassium Ferricyanide. Note that it does not
decompose to form cyanide in the body which means that
you need something stronger than stomach acid.

Treat all darkroom chemicals with respect. It is good to
read the MSDSs for the various chemicals you use, but it
can help to remember that they tend to be written in a way
which makes any chemical sound scary.


Yeah, I agree with all of that... but it's good to know. Sometimes
people dont realise the effects that these can have, though, because
they're "just photography solutions... they cant do any harm". Tip it in
the sink with brick cleaner from the hardware shop, for example, and
it'll be quite different!

The MSDS is a good idea, but I agree that they can sound bad. The MSDS
for water is available at some sites, as is the one for salt etc...
you'd never touch anything again if you took them too seriously (not
that I advocate taking them lightly, but a little knowledge and some
common sense never goes astray!)

Scott.

Peter Irwin wrote:
Scott Coutts wrote:

Nicholas O. Lindan wrote:

You want something called "Farmer's Reducer". It is a mixture of
Pot. Ferricyanide (pretty-much non-toxic, despite the name)

Unless you accidentally mix it with something acidic in your darkroom...
then you get cyanide gas (:


This has been discussed before. It takes quite a bit to
decompose Potassium Ferricyanide. Note that it does not
decompose to form cyanide in the body which means that
you need something stronger than stomach acid.

Treat all darkroom chemicals with respect. It is good to
read the MSDSs for the various chemicals you use, but it
can help to remember that they tend to be written in a way
which makes any chemical sound scary.


Yeah, I agree with all of that... but it's good to know. Sometimes
people dont realise the effects that these can have, though, because
they're "just photography solutions... they cant do any harm". Tip it in
the sink with brick cleaner from the hardware shop, for example, and
it'll be quite different!

The MSDS is a good idea, but I agree that they can sound bad. The MSDS
for water is available at some sites, as is the one for salt etc...
you'd never touch anything again if you took them too seriously (not
that I advocate taking them lightly, but a little knowledge and some
common sense never goes astray!)

Scott.

"Nicholas O. Lindan" wrote in message
k.net...
"Richard Knoppow" wrote

Iodine has the advantage that the reduced area
will not develop a yellow stain over time.

Interesting ... what causes the yellow stain [or better
yet, what won't cause the yellow stain]?

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

Probably residual silver complex from the bleach. For
normal Farmer's reducer, where the hypo and bleach are
combined the hypo isn't sufficient to remove all the silver
complex. Materials reduced in Farmer's should be refixed and
washed. I am not certain why the Iodide reducer doesn't
cause a stain, perhaps it does if treated with hypo. The
original reducer used Potassium cyanide as the fixing agent.
Cyanide is the most effective fixer there is but is extemely
toxic and can also dissolve some image silver. Another
version of Iodine reducer uses Thiocarbamide as the fixing
agent. This is also very effective but I think also needs a
final fixing step.
Sepia toned images are not subject to the yellowing
because the sulfide redeveloper has already converted all
remaining silver complexes to silver sulfide.


--
---
Richard Knoppow
Los Angeles, CA, USA

"Nicholas O. Lindan" wrote in message
k.net...
"Richard Knoppow" wrote

Iodine has the advantage that the reduced area
will not develop a yellow stain over time.

Interesting ... what causes the yellow stain [or better
yet, what won't cause the yellow stain]?

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

Probably residual silver complex from the bleach. For
normal Farmer's reducer, where the hypo and bleach are
combined the hypo isn't sufficient to remove all the silver
complex. Materials reduced in Farmer's should be refixed and
washed. I am not certain why the Iodide reducer doesn't
cause a stain, perhaps it does if treated with hypo. The
original reducer used Potassium cyanide as the fixing agent.
Cyanide is the most effective fixer there is but is extemely
toxic and can also dissolve some image silver. Another
version of Iodine reducer uses Thiocarbamide as the fixing
agent. This is also very effective but I think also needs a
final fixing step.
Sepia toned images are not subject to the yellowing
because the sulfide redeveloper has already converted all
remaining silver complexes to silver sulfide.


--
---
Richard Knoppow
Los Angeles, CA, USA

"Nicholas O. Lindan" wrote in message
k.net...
"Richard Knoppow" wrote

Iodine has the advantage that the reduced area
will not develop a yellow stain over time.

Interesting ... what causes the yellow stain [or better
yet, what won't cause the yellow stain]?

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

Probably residual silver complex from the bleach. For
normal Farmer's reducer, where the hypo and bleach are
combined the hypo isn't sufficient to remove all the silver
complex. Materials reduced in Farmer's should be refixed and
washed. I am not certain why the Iodide reducer doesn't
cause a stain, perhaps it does if treated with hypo. The
original reducer used Potassium cyanide as the fixing agent.
Cyanide is the most effective fixer there is but is extemely
toxic and can also dissolve some image silver. Another
version of Iodine reducer uses Thiocarbamide as the fixing
agent. This is also very effective but I think also needs a
final fixing step.
Sepia toned images are not subject to the yellowing
because the sulfide redeveloper has already converted all
remaining silver complexes to silver sulfide.


--
---
Richard Knoppow
Los Angeles, CA, USA

"Richard Knoppow" wrote

"Nicholas O. Lindan" wrote in message
"Richard Knoppow" wrote

[Farmer's Reducer may] develop a yellow stain over time.

Interesting ... what causes the yellow stain?

Probably residual silver complex from the bleach. For
normal Farmer's reducer, where the hypo and bleach are
combined the hypo isn't sufficient to remove all the silver
complex. Materials reduced in Farmer's should be refixed and
washed.

Ah, relief - do that already.

I don't really use Farmer's: I dip the photo into a ferri-only
solution for 5 seconds or so and then into fixer, let the
fixer work and then examine the image. Repeat as necessary.
For prints I make a lot of, or that just need a homeopathic
highlight cleansing, I have established times in the ferri.

I gave up observing the bleaching while it was happening
using a ferri-fix (Farmer's) bath, I found it to
be nerve wracking, unrepeatable and prone to run-away --
really, really clear midtones...

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

"Richard Knoppow" wrote

"Nicholas O. Lindan" wrote in message
"Richard Knoppow" wrote

[Farmer's Reducer may] develop a yellow stain over time.

Interesting ... what causes the yellow stain?

Probably residual silver complex from the bleach. For
normal Farmer's reducer, where the hypo and bleach are
combined the hypo isn't sufficient to remove all the silver
complex. Materials reduced in Farmer's should be refixed and
washed.

Ah, relief - do that already.

I don't really use Farmer's: I dip the photo into a ferri-only
solution for 5 seconds or so and then into fixer, let the
fixer work and then examine the image. Repeat as necessary.
For prints I make a lot of, or that just need a homeopathic
highlight cleansing, I have established times in the ferri.

I gave up observing the bleaching while it was happening
using a ferri-fix (Farmer's) bath, I found it to
be nerve wracking, unrepeatable and prone to run-away --
really, really clear midtones...

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
To reply, remove spaces: n o lindan at ix . netcom . com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

On Thu, 31 Mar 2005 13:16:09 +1100, Scott Coutts
wrote:

Nicholas O. Lindan wrote:
You want something called "Farmer's Reducer". It is a mixture of
Pot. Ferricyanide (pretty-much non-toxic, despite the name)

Unless you accidentally mix it with something acidic in your darkroom...
then you get cyanide gas (:

Scott.


mar3105 from Lloyd Erlick,

How strong would the acid have to be to evolve cyanide
gas from potassium ferricyanide?

My understanding is that only very strong acid, like
concentrated sulfuric or nitric, will cause this
reaction.

There isn't much call for strong acids in a regular
darkroom, so it's easy to keep them out.

regards,
--le
________________________________
Lloyd Erlick Portraits, Toronto.
voice: 416-686-0326
email:
net: www.heylloyd.com
________________________________
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