From: Charles Steinmetz (csteinmetz@netexpressway.com)
Date: 01/06/02-04:21:36 AM Z
[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)
_____________________________________________
Free email with personality! Over 200 domains!
http://www.MyOwnEmail.com
This archive was generated by hypermail 2b30 : 02/15/02-11:47:41 AM Z CST