Re: fast carbon emulsion

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From: Jarred J. McCaffrey (jmccaffr@cs.uml.edu)
Date: 05/30/00-09:53:34 PM Z


Great to hear someone was interested in testing. I don't have the
equipment or chemicals available just yet to do this myself. Please tell
us of the success or failure of the formula.

BTW, I just subscribed to your carbon list. Thanks!

Jarred

On Tue, 30 May 2000, Wayde Allen wrote:

> On Mon, 29 May 2000, Jarred J. McCaffrey wrote:
>
> > I would like to experiment with some very large (handmade) negatives in
> > homebrewed cameras. Carbon has been touted in more than one book as being
> > a faster printing emulsion than silver based processes. E.J. Wall wrote
> > of a formula for carbon transfer which only required 1/4 second exposure.
> >
> > Is it the experience of list members that carbon gelatin emulsions are
> > potentially faster than handmade (not commercial) silver based emulsions?
>
> I can't say that my pigmented gelatin (carbon) emulsions are very fast.
> Carbon is typically a contact printing process for the same reasons as the
> other alt processes, and have similar exposure times.
>
> I once did try exposing a sheet of carbon tissue in my 4x5 camera. I did
> get what looks like a useable negative, but the exposure time was 2 hours!
>
> > Is there a faster process that might better suit the handmade film
> > purpose?
>
> To the best of my knowledge, silver gelatin is the fastest chemical
> process that we know of.
>
> > Whether or not carbon is the ideal choice, I would greatly
> > appreciate postings of fast carbon emulsion formulas from your experience
> > or advice on creating a fast carbon emulsion.
>
> You probably want to consider subscribing to my carbon mailing list
> <http://rmp.opusis.com/mailman/listinfo/carbon>. Several of us have been
> brainstorming ways to improve on the process, and possibly make it faster.
> I also have a comparison of some carbon tissue recipe's and other bits and
> pieces of info at <http://rmp.opusis.com/carbon/carbon.html>. I'm working
> to expand this collection of data as my time permits. If nothing else,
> you might be interested in the gallery of carbon images
> <http://rmp.opusis.com/carbon/gallery.html>.
>
> > As a starter here are two fast carbon emulsions from E.J. Wall's _The
> > History of Three-Color Photography_. I have quoted the text exactly.
> >
> > (p 692)
> >
> > W. Wadhams, A. Ziehm, H. A. Sonderman and P. Woithe patented a
> > modification of the dichromate sensitizer, which is stated to give great
> > speed in printing. One formula is:
> >
> > Potassium dichromate 30 g.
> > Magnesium chloride 10 g.
> > Sodium acid phosphate 5 g.
> > Water 1000 ccs.
>
> One of the guys on the carbon list is preparing to test this recipe.
> Possibly in the next week or so.
>
> - Wayde
> (wallen@boulder.nist.gov)
>
>


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