[pure-silver] Re: Are most photographers visual learners... a little OT
- From: Richard Knoppow <dickburk@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sun, 11 Nov 2007 01:29:06 -0800 (GMT-08:00)
-----Original Message-----
>From: Laurence Cuffe <cuffe@xxxxxxx>
>Sent: Nov 10, 2007 9:25 PM
>To: pure-silver@xxxxxxxxxxxxx
>Subject: [pure-silver] Re: Are most photographers visual learners... a little
>OT
>
>
>On Saturday, November 10, 2007, at 03:37PM, "Dave V" <DValvo@xxxxxxxxxxxxxxxx>
>wrote:
>>Sorry to mislead. I will disclose answer later, was wondering if others
>>knew.
>>
>>----- Original Message -----
>>From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
>>To: <pure-silver@xxxxxxxxxxxxx>
>>Sent: Saturday, November 10, 2007 3:28 PM
>>Subject: [pure-silver] Re: Are most photographers visual learners... a
>>little OT
>>
>>
>A nice question.
>Previous to 1900 I don't believe that the quality of plates was well
>controlled. My evidence for this is circumstantial and is based on the
>widespread prevalence of development by inspection, which allows one to
>compensate for limited errors in exposure. In addition to this the use of
>various reducing formulae to control the contrast characteristics of the
>negative also seems to have been widespread.
>In the 1870's Swann developed the dry plate process which was a trade secret
>until revealed by Bennet. Mr Eastmann read Bennets paper in the BJP and
>traveled to London where he was unimpressed by the state of the art English
>facility for coating plates, where it was all done by hand.
>Eastmann returned to the states where he developed a two layer process where
>the silver containing emulsion is coated onto a paper backing which was
>pre-coated with gelatin. The resultant combined coating could be striped from
>the paper backing and coated onto standard glass plates.
>The next substantial development was flexible transparent backing for the
>emulsion, presumably cellulose nitrate bu I dot know how this was coated.
>How am I doing Prof Valvo?
>
>All the best
>Laurence Cuffe
>
I am away from home and my books at the moment.
I think you are confounding two things here, one is the method of making dry
plates and the other was Eastman's first attempt at a flexible support for a
roll film camera.
Eastman was coating on glass early on using glass covered tables to cast the
emulsion. The paper backing was used for the early flexible film before the
discovery of using cellulose nitrate base. The film was sent back to Kodak for
processing where the emulsion was stripped off the paper for printing.
Eastman's first trip to England was to investigate the source for his
gelatin. In an oft repeated story Eastman found that his plates were lacking in
sensitivity and contrast. He traced this down to the gelatin and found, after
some investigation, the the source in England had switched their source for the
skins or bones they used to produce the gelatin. When they supplied gelatin
from the original source the emulsion again worked as expected. It was some
twenty or more years before the actual cause of the problem was discovered.
Eastman also talked to C.E.K.Mees, I think on a later trip. Mees was a
partner in Wratten and Wainwright, a producer of very good dry plates and
photographic light filters. W&W had good knowledge of German dyes both for
sensitizing and for filtering. Mees agreed to go to work for Eastman provided
he bought out Mees's partners and allowed them to continue running the company.
Eastman did this and Mees set up Kodak's first research laboratory (in 1912).
Its quite possible that Eastman was interested in devising a process for
practical color photography as well as just improving the quality of his
products. The knowledge of color sensitization that W&W had would have been
very useful in this way.
Eastman had a number of patents on coating machinery. Do a name search for
him on Google Patents.
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
Los Angeles, CA, USA
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
