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Tmax & D-76



 
 
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  #21  
Old August 6th 10, 07:20 AM posted to rec.photo.darkroom
Richard Knoppow
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Posts: 751
Default Tmax & D-76


"Jean-David Beyer" wrote in message
...
Richard Knoppow wrote:

Being big is not always an advantage. Years ago I came
across a very
interesting paper called "On Being the Right Size". I
can't remember
the author, it was in an anthology of papers on either
mathematics or
physics published by _Scientific American_ magazine.
Maybe a web
search would find it.

It can be found in The World of Mathematics, Volume 2,
pages 952 ff.
"On Being the Right Size" by J.B.S. Haldane. Haldane, J.
B. S. (March
1926). "On Being the Right Size". Harper's Magazine.


--
.~. Jean-David Beyer Registered Linux User
85642.
/V\ PGP-Key: 9A2FC99A Registered Machine
241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 15:10:01 up 11 days, 18:02, 3 users, load average:
5.12, 4.86, 4.80


That's it! Thanks, I thought it was in that series.



--
Richard Knoppow
Los Angeles, CA, USA



  #22  
Old August 6th 10, 08:11 PM posted to rec.photo.darkroom
Richard Knoppow
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Posts: 751
Default Tmax & D-76


"Digitaltruth" wrote in message
...
MSDS are designed for health and safety, so although they
can provide
very useful information about specific formulas, my
understanding is
that there is no requirement to list any chemical that
constitutes
less than 5% of the total volume (unless, I presume, it
would be
hazardous in such a concentration).

While the current MSD sheets for Perceptol and Microdol-X
do list the
same composition, there is no way to know what other
chemicals under
5% are included. Older MSD sheets for Microdol-X list
Boric Anhydride
and Sodium Hexametaphosphate in concentrations of less
than 1%, and as
Richard points out, there may be multiple different
historic MSDS out
there listing other ingredients.

In the Film Developing Cookbook (1st edition, 1998) Bill
Troop states
that the exact formula for Microdol-X is proprietary and
unpublished.
While the general formula for the original Microdol is now
common
knowledge, Troop points out that its successor,
Microdol-X, differs
from this earlier formula as it contains an
anti-silvering agent,
which he suggests is probably a benzophenone anti-staining
agent.

In speaking to Bill about this difference a few years ago,
the
understanding I came away with was that the anti-staining
agent
contained in Microdol-X is not incorporated in Perceptol,
and this is
the key difference between the products. Troop says in his
book that
the formulas are "chemically close." Perhaps they are
close enough for
development times to be the same, but I would want to have
more
information from experienced users who have done
side-by-side testing.


The problem is how does Bill Troop know what is in
Perceptol? I have used it exetensively with T-Max and have
never seen a hint of dichroic fog.
Kodak has a bunch of patents on anti-silvering agents,
which it also calls anti-fog agents in some places. Such
agents are used in many places including emulsions. Who
knows which, if any, were used in Microdol-X.
Note that the former Kodak extra-fine-grain developer
DK-20 employed a silver solvent namely thiocyanate. It
became useless for modern films because of the serious
dichroic fog it produced.
BTW, I think I may have referred to D-20 in an earlier
part of this thead, I meant D-23. Bad memory.



--
Richard Knoppow
Los Angeles, CA, USA



  #23  
Old August 6th 10, 08:31 PM
Keith Tapscott. Keith Tapscott. is offline
Senior Member
 
First recorded activity by PhotoBanter: Feb 2005
Posts: 112
Question

Quote:
Originally Posted by Richard Knoppow View Post
Kodak is reportedly discontinuing D-76, Microdol-X, and
Kodak Hypo Clearing Agent.
--
Richard Knoppow
Los Angeles, CA, USA
I am aware that Kodak have discontinued Microdol-X, D-76R replenisher and the larger packaged sizes of D-76, but I have not read about the regular hobby sizes of D-76 being discontinued.
Where did you read about Kodak D-76 being discontinued altogether?
 




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