Re: Demachy and Maskell's postscript

Katharine,
Yes, I did try this two summers ago. I noticed in the literature that it
was a method in vogue at the beginning, and then it fell out of favor
shortly thereafter, as it was not found to be faster, especially 4-5 times
faster, as Demachy had said. I"ve got all my notes chronologically organized
and in the near future could dig up when the books started saying it wasn't
what it was cracked up to be.

The thought at the time was that the dichromate would be on the surface of
the paper and better secure the halftones because it would harden from the
bottom up. It's interesting, because I read in solarplate literature (not
sure what the sensitizer is in solarplate) that it hardens from the base up.
Isn't that odd? Why would light hitting the surface harden the depths first
and not the top? But that is a digression.

I did find it was more contrasty, therefore looked sharper, and did not find
more stain either in pigment or dichromate.

To me, the method did not make a bit of sense because it required two steps
instead of one, and if there weren't benefits, why bother.

However, I have to remember that in those days also in vogue was a thicker
coat with lots of exposure, with carbon blacks and oxide reds and that type
of thing, one coat gums, so maybe it might excel in that scenario. In other
words, I haven't thrown out the method as a no go yet.
Chris
PS I've been going through old Camera and Darkroom mags, and what a hoot.
Two articles by Jan Pietrzak, and a gum image of Judy Siegel's. Two gum
articles by Steve Anchell. I keep looking for alt listers....
----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, April 08, 2005 10:18 PM
Subject: Demachy and Maskell's postscript

> As you know, I don't usually spend much time reading historical
> literature about gum printing or trying to replicate old techniques,
> because I've never seen much useful information come out of such
> investigations. (Not to denigrate those who do enjoy this kind of work,
> but only to say it's not for me).
>
> But in a private correspondence with a chemist who knows some things
> about some other processes but zero about gum printing, (maybe I should
> specify that this is no one on this list) he appealed to the method
> outlined in the Demachy postscript to support a point he was making, and
> asked hadn't I ever tried that. I hadn't, and didn't figure I could say
> anything about it without having tried it, although now that I think
> about it, his not having tried it himself didn't keep him from having an
> opinion about its usefulness to the discussion. But I digress.
>
> So, I tried it, with spectacular lack of success. For those not familiar
> with this, Demachy was recommending soaking the paper in potassium
> dichromate, drying it bone dry, then coating with gum and pigment, with
> some water added to make it spreadable. He claimed this two-part
> emulsion eliminated stain and what's more was 4 or 5 times faster than
> the pre-mixed emulsion.
>
> I tried it four times, with four different papers. Each time, I not only
> got pigment stain with my usual amount of pigment, but dreadful brown
> dichromate stain; I never get either with my usual practice. What's
> more, the two-part emulsion, if anything, was slower than the mixed
> emulsion, contrary to the claims in the article.
>
> So, I'm curious. Has anyone ever tried this and got better results? The
> fact that this method has not survived or been revived by gum
> revivalists over the decades suggests to me that I'm not the only one
> who hasn't been able to make it work, but if someone has I'd be
> interested in hearing about it.
>
> I know that one argument when one can't replicate old techniques is that
> the papers and stuff were different then. But I have a hard time
> imagining how a different paper would print four times faster if it were
> soaked in dichromate first-- what that paper would have to be like for
> that to be the case.
>
> If anyone's interested, I'll be glad to scan test prints to look at.
>
> Katharine Thayer
>
Received on Sun Apr 10 07:11:59 2005