From: Richard Knoppow on

"Keith Tapscott." <Keith.Tapscott..55f41c7(a)photobanter.com>
wrote in message
news:Keith.Tapscott..55f41c7(a)photobanter.com...
>
> Most B&W developers contain Hydroquinone with either Metol
> or Phenidone
> or a Phenidone derivative. Both Metol and Phenidone are
> super-additive
> with Hydroquinone, so why add both of them in the same
> developer
> formula?
>
> Here is an example of a developer which contains all three
> of those
> constituents.
> http://www.tetenal.com/sidaopener_uk.htm?file=sidauk/100152.pdf
>
>
>
>
> --
> Keith Tapscott.


I've wondered the same thing. There are a number of
developer formulas that have more than two developing agents
in them, sometimes puzzeling combinations. My chemistry is
not good enough to know why.


--
--
Richard Knoppow
Los Angeles, CA, USA
dickburk(a)ix.netcom.com


From: Richard Knoppow on

"Keith Tapscott." <Keith.Tapscott..55f41c7(a)photobanter.com>
wrote in message
news:Keith.Tapscott..55f41c7(a)photobanter.com...
>
> Most B&W developers contain Hydroquinone with either Metol
> or Phenidone
> or a Phenidone derivative. Both Metol and Phenidone are
> super-additive
> with Hydroquinone, so why add both of them in the same
> developer
> formula?
>
> Here is an example of a developer which contains all three
> of those
> constituents.
> http://www.tetenal.com/sidaopener_uk.htm?file=sidauk/100152.pdf
>
>
>
>
> --
> Keith Tapscott.

Its interesting also that it contains both potassium
carbonate and sodum metaborate. There are some developers,
notably Kodak D-7, a pyro-metol developer, where the metol
serves mainly as a preservative for the pyro. Metol is a
prodigeous oxygen absorber. Its also curious that its the
only ingredient in the MSDS which has detailed hazards
although hydroquinone is usually considered more hazardous
than metol.


--
--
Richard Knoppow
Los Angeles, CA, USA
dickburk(a)ix.netcom.com


From: Richard Knoppow on

"Keith Tapscott." <Keith.Tapscott..5633638(a)photobanter.com>
wrote in message
news:Keith.Tapscott..5633638(a)photobanter.com...
>
> Richard Knoppow;848656 Wrote:
>>
>> Its interesting also that it contains both potassium
>> carbonate and sodum metaborate. There are some
>> developers,
>> notably Kodak D-7, a pyro-metol developer, where the
>> metol
>> serves mainly as a preservative for the pyro. Metol is a
>> prodigeous oxygen absorber. Its also curious that its the
>> only ingredient in the MSDS which has detailed hazards
>> although hydroquinone is usually considered more
>> hazardous
>> than metol.
>>
>> Richard Knoppow
>> Los Angeles, CA, USAWhat I also found interesting was
>> that there was no mention of the
> preservative(s) or of any restrainer(s). It makes you
> wonder if
> sulphite alone is the preservative, or whether it contains
> sulphite and
> bisulphite or metabisulphite.
> It may or may not contain a restrainer or perhaps it
> contains more than
> one restrainer.
>
>
>
>
> --
> Keith Tapscott.

Well, keep in mind that MSDS are legal not scientific
documents and are often written as much to obscure the
formula as anything else. MSDS do not have to list materials
which are considered harmless or which are present in small
amounts. Also, I think this is a copy of a German MSDS where
the rules may be different than in the US. An example is
T-Max developer. AFAIK these contain a form of Phenidone but
its not mentioned in the MSDS, at least the older ones.
There are other substances that fill the function of
sulfite, they are found in liquid concentrates, see the MSDS
for developers like HC-110 for example.
Sometimes better information can be found in patents
but they can also be written to obscure information.


--
Richard Knoppow
Los Angeles, CA, USA
dickburk(a)ix.netcom.com