Just FYI, since you like old books, there’s an outfit called Forgotten Books
(www.forgottonbooks.com) which is madly reprinting obscure out-of-copyright
books — either as ebooks or hardcopy. They have a large selection of
photography books, the biggest problem being that it’s a big disorganized
hodge-podge of titles .
So far I’ve purchased “The First Book of the Lens” by C. Welbourne Piper (no
date) and “Handbook of Photography” by Keith Henny and Beverly Dudley (1939).
The first is actually a pretty good introduction to photographic optics. I
haven’t yet really dug into the second one.
On Nov 14, 2019, at 11:51 AM, `Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
I have been reading the old photographic chemistry book by Crabtee and
Mathews, two of Kodak's top researchers. The book was published in 1938. It
is old enough to have the old charts showing the rate of fixing vs: fixer
concentration. These show a broad dip in fixing time at a specific
concentration. It turns out this was a blunder in the measurement; the film
was dry when put into the fixer. When thoroughly wetted film was used the
fixing rate continued to increase with concentration until saturation. This
probably had some effect on the choice of fixer concentration in Kodak
formulae but maybe not much.
It is also interesting that the hardening properties of a fixing bath were
stressed over its ability to completely fix out the image. Hardening was
important because the emulsions of the time were quite soft. In fact, if one
looks at recommendations of the time one finds the standard temperature is
65F. It was increased to 68F later because the emulsions were made harder.
Ammonium thiosulfate fixers are mentioned but ammonium thiosulfate was
expensive at the time and hard to transport. It is still mostly supplied as a
liquid concentrate.
Ammonium thiosulfate fixer (rapid fixer) has the advantage of dissolving
silver iodide much more readily than sodium thiosulfate. Many emulsions,
including some paper emulsions, now have enough silver iodide to justify the
use of rapid fixer since the fixing times in sodium fixer can be pretty long.
The book has almost nothing about color photography in it. Color films of
the chromogenic type (Agfacolor, Kodachrome) had been on the market for only
a couple of years. Earlier films like Autochrome and Finley color, are really
combinations of various methods of combining black and white emulsions with
built in filters. Actually except for the early Kodachrome which a lenticular
film using a filter over both taking and projecting lens.
More tidbits as I encounter them. This is still a very usable book in many
ways. A great deal of the stuff was carried over to other Kodak publications
for many years.
We have better films, better developers, better fixing baths now and a
better understanding of how the process works. But the actual photography and
darkroom procedures have not much changed.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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