Re: Gum Bichromate Kit from Photo. Formulary

Gumprint@aol.com
Fri, 19 Jul 1996 13:38:40 -0400

In a message dated 96-07-19 12:13:43 EDT, you write:

<<
Well, the FAQ are now in the form of WEB page, and I can't (or maybe don't
know how to download the articles or part of an article). I actually like
the
old format better (when you can send a request and have the FAQ sent to you.
Can one still do that, by the way?)

Scopic's book doesn't show how to use a light box as the light source. I
have
a 12x18 light box for viewing slides. It has color-corrected tubes in it
(5000 deg. K). Can I use it for the light source? What is a starting point
for exposure time?

Also, do I have to worry about the unevenness of the light? Since it has
only
a frosted acrylic over the tubes, the light is brighter near the tubes. Do I
need another piece for acrylic so that the light will be more even?

I am thinking about laying down the negative, sensitized paper, a mouse pad,
a piece of glass or plywood, and finally a book (for weight) over the light
box. Do you think this will work?

Another question is how can I walk out of the darkroom when the paper is
being exposed? Do I have completely light-proof the exposure system?

Thanks in advance for any help/suggestion.

>>
Greetings Dave

The following is the information regarding the archives:

To find out about the archives you will have to enlist the services of
listproc@cse.unsw.edu.au. I believe the command to see a list of what
is available is "INDEX alt-photo-process" (sans quotes). Send the
command to the listprocessor as the body of your message. The GET
command is used to retrieve the archives. For more information about
how to use the GET command and for other commands available send the
listprocessor a message that just says HELP.

******************************************************************************

Hi all,
Looks like I might have to go over this once a month or so for people
who have forgotten... That's okay, just let me answer questions like
this...

To get the faq, send the message

get alt-photo-process faq

to listproc@cse.unsw.edu.au (note that faq is lowercase).

To get the archive for a particular month, send the message

get alt-photo-process archive-9403

to listproc@cse.unsw.edu.au. 9403 is the year and month of the archive
you want. March 1994 is the first one, and all bar the current month are
available.

To unsubscribe from the list, send the message

unsub alt-photo-process

to listproc@cse.unsw.edu.au.

To change to digest format, send the message

set alt-photo-process mail digest

to listproc@cse.unsw.edu.au. If you wish to turn off mail for a while,
change "digest" to "postpone". When you return, change "postpone" to
"ack" to switch mail back on.

If you are confused, and want the listproc to help you, send the
message

help

to listproc@cse.unsw.edu.au.

In all cases, requests go to the address "listproc@cse.unsw.edu.au",
not to the list. If you have any problems whatsoever regarding the list,
feel free to email me direct (stevea@sedal.usyd.edu.au).

cheers
-steve

******************************************************************************
************

That ought to help you with the list questions.
Onto the light source.

You can print by the sun if you have no other UV source. I don''t think you
will have any luck with a light box. I use a bank of 8 24" uncoated BL bulbs
that are built to be in a kitchen type cabinet. I can be printing with the
doors closed and not have any retina damage. There is no acrylic sheet
between the bulbs and the printing frame. A typical initial exposure to set
highlights would be about seven minutes at a distance of 4 inches. I use a
Premier type contact printing frame.

You mention putting weight on top of a mouse pad with glass, etc. Gum
printing is normally multiple exposure and therefore the negative and paper
have to be in registration with each emulsion and exposure. How would you
realign everything? Perhaps you are after a single emulsion. I have been
making gums since 1978 and have not made a successful single emulsion yet.
Heavy concentrations of pigment in the emulsion will cause staining, an
effect I do not like. The other end of single printings is a flat muddy
print.

I do not understand your question regarding leaving the darkroom. Please
elaborate.

My intention is not to discourage you about gum bichromate. It's very fussy.
I have tested all the Winsor and Newton tubed watercolor pigments for
staining ( maximum pigment:gum arabic ratio) and for greatest shadow
separation. The variables go on and on. Development can be in still baths
or under a hose. Some people develop for 24 hours! My work is
non-manipulative and I keep every variable I can constant. I use Rives BFK
for it's tooth and hand size each piece with 3 gelatin/chrome alum baths. I
bought a ream of it in 1980 and figure I won't use it up for another 20
years. I weigh the pigments on a gram scale and use syringes to measure the
gum arabic. It's important that I be able to duplicate results. But that's
just me.

Try the set up you've come up with and see what happens.Mix the dichromate
solution with the pigment/gum solution in small batches and do some tests
with the light sources you have available including the sun. If you can use
a split back printing frame you can (sort of) print by inspection.

I hope this helps. Feel free to contact me.

Carole