[rollei_list] Re: Rolleiflex 2.8C and two developers
- From: CarlosMFreaza <cmfreaza@xxxxxxxxx>
- To: "rollei_list@xxxxxxxxxxxxx" <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 1 Feb 2014 09:26:03 -0200
For Chemistry in general, "stock solution" is a solution that can't
be used for its purposes directly, needing to be diluted to obtain a
working solution, it was the reason I wrote from the beginning Mr
Chris Burck was right _in general_; a clear sample in the photographic
world are the Kodak HC110 and Beutler A+B developers, the stock
solution can't be used as working solution and you need to dilute it
for a working solution. In other words, Kodak HC110 and Beutler
developers fit in the general definition. However it does not happen
for several developers, they don't fit in the general definition
because they are stock solutions and working solutions simultaneously.
If I mix and prepare Microdol, Microphen, ID11, Perceptol and the
like, I can use the original solution as working solution, it would be
a "full strength" working solution; but this original solution is also
a "stock solution" for two reasons: 1) I can dilute it to obtain a
different working solution, it will be a _working solution only_
because the solution will be discarded completely after to use it
once, a one shot developer for most cases.- 2) You can use and reuse
the the original solution several times keeping it in stock, as the
word "stock" indicates.
I use the Kodak T-Max Rs developer as stock solution and working
solution simultaneously. The Tmax RS developer does not exist before
to mix Parts A and B and adding water to complete 1 gallon, the
original liquids are separated parts, they need to be mixed to be a
developer and they are mixed with water, _the developer is not diluted
in water since it does not exist without the water_ , the water is a
developer part as Part A and Part B, it's a third part. After you
obtained this final product, the T-Max RS developer formed with
A+B+water you could talk about to dilute this _stock solution_ or not.
I did not dilute my TMax RS stock solution, I use it as working
solution and I have it in stock from two years ago.
Carlos
2014-02-01 Richard Knoppow <dickburk@xxxxxxxxxxxxx>:
>
> Of course, this isn't exactly how T-Max RS works, because
> the typical
> dilutions do not extend conveniently. If standard dilution
> is 1:4, to take
> some of this solution and dilute it further to 1:9 is
> inconvenient since it
> isn't a direct ratio. Not to mention the fact that this new
> dilution can
> no longer be incorporated back into the original working
> strength mixture
> (especially since 1:9 is not a one-shot dilution, or at
> least, doesn't have
> to be). In other words, the normal practice is going to be
> to mix the
> entire bottle of concentrate at the same dilution, and keep
> it that way.
>
> This is Kodak being confusing 1:9 is the mixed stock
> diluted to half strength. The "normal" working developer is
> the concentrate mixed 1 part concentrate wtih 4 parts water
> to make up the final amount. Total 5 parts. 1:9 is one
> part concentrate diluted with 9 parts water to make up a
> total of 10 parts or half strength. You can take the 1:4
> mixture and dilute it with an equal amount of water to get
> the same thing.
> Kodak uses very old chemical terminology for their
> dilutions. Most chemists would describe the 1:4 mixture as
> 1:5 meaning 1 part of the substance to a total of five
> parts. The same thing is seen with, say, D-76 where we
> typically say its diluted 1:1 to mean half stength, i.e.,
> one part substance and one part diluent where most chemists
> would call it 1:2 or one part substance to a total of two
> parts.
> Perhaps we should also introduce the term "concentrate" This always
> refers to a liquid solution. The concentrate is mixed wtih water to produce
> a stock or a working solution. "Stock" solution usually also means a
> concentrated solution that is not used directly for development or other
> processes. An example is a print developer, say, Dektol. Decktol comes as a
> poweder. It is mixed in a given solution of water and brought up to a
> specified volume. This is a concentrate although usually called a "stock"
> solution. To use it this stock is diluted with some amount of water, in the
> case of Dektol one volume of the stock to two volumes of water, by Kodak
> terminolog 1:2, total three volumes. This is the working solution. Some
> developers, mostly those in powder form, are used directly from the mixed
> solution. They may also be diluted but not always. Examples of such
> developers are Microdol-X and Perceptol and D-76. Microdol-X and Perceptol
> have properties that change when they are diluted. These two, which are
> identical, are extra-fine-grain developers. When diluted they lose their
> extra-fine-grain property but deliver a higher film speed. D-76 is often
> diluted half and half with water to obtain reasonably long development
> times. Its chemical nature is such that its characteristics when diluted are
> very little different from the full strength solution. The full strength
> solution of these developers is not strictly a stock solution even though
> they can be diluted for use.
> So, we have; concentrate, stock, working.
> Anyway, I hope this makes things clearer.
>
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk@xxxxxxxxxxxxx
>
>
>
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