From: Tox Gunn (tox@remarque.org)
Date: 01/06/02-11:44:59 AM Z
Thanks for sharing this with the rest of us!
Tox
At 04:21 AM 1/6/2002 -0600, you wrote:
>[My apologies if two similar messages appear -- I'm resending because the
>first one appears to be lost in the ether.]
>
>Hi Ken,
>
> > What do you sub glass with?
>
>Sodium silicate. That and isinglass are the most common subs. A thin
>chrome-hardened gelatin layer (which may also have sodium silicate in it)
>can be used, as well as albumen. A number of modern polymers also
>work well.
>
>You want to start with surgically clean glass. I use hot soapy water
>followed
>by a hot tap water rinse, an acetone bath, boiling in a strong sodium
>hydroxide
>solution, a boiling tap water rinse, and finally a boiling distilled water
>rinse.
>
> > Is "photographic gelatin" not the pure stuff that needs everything added
> > back in for sensitivity?
>
>That all depends. Unless your supplier can give you a complete analysis
>and tell you the ingredients (hide? bone? hooves? of what animal?) and the
>process (there are acid and alkaline processes, with many variations of
>each) used to make it, you just never know what you're getting. Most of
>the suppliers who will sell the small quantities you need don't have any of
>this information. The Big Boys test each lot and adjust -- even lots with
>similar provenance and analyses don't work the same.
>
> > Is the bloom rating important?
>
>Not unless you care about high-temperature processing.
>
> > As for coating. I was thinking of following Eastman. He had a roller in a
> > trough. I was planning on "rolling" the glass over the roller
>that is in
> > contact with he gelatin emulsion in the trough. If the glass is relatively
> > warm I was hoping that it would level itself out before setting. Any
>input?
>
>That should work. I've gotten good results by pouring a measured amount
>of emulsion onto a plate and leveling by tilting, as with collodion. I
>graduated
>to a moving hopper with a slit, which deposits an even layer on a warm
>plate.
>Lay the coated plate on a leveled, chilled slab to set the emulsion in a
>minute
>or two and dry in a dust-free area for 8 hours or so (preferably not above
>55F).
>
> > As for books. If you would feel comfortable to loan one of them to me for
> > copying it would be appreciated.
>
>Mine are full of notes and underlining, so they aren't really good ones to
>copy.
>None of them is hard to get through interlibrary loan.
>
> > My understanding was that
> > Gelatin emulsions, any emulsion, would be faster than collodion. I shoot
>my
> > collodion images at f11 / 16 for three seconds. I believe this is a ASA
> > rating or 1/3 or 1/6?
>
>The Kodak AJ-12 emulsion is comparable in speed to collodion. Ammoniated
>emulsions are several stops faster. Ripened and doped emulsions can be as
>fast as you want, but fogging is a real problem.
>
> > My first goal was to only make orthochromatic, sorta, type of film. It
> > seemed that the addition of only one common dye would do this. Ethyl Red
>is
> > what I was planning on using.
>
>I strongly suggest getting blue-sensitive emulsions down first. Color
>sensitizing
>opens a whole new universe of challenges.
>
> > So could you pass along what equipment you are using to make your
>emulsion?
>
>I use glass and glazed pottery beakers, a magnetic stirrer, and burettes for
>injection.
>
>
>Best regards,
>
>Charles (sorry for the spam below)
>
>
>
>
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