Re: Back-exposing on plastic (was: Re: Gum transfer

From: Yves Gauvreau ^lt;gauvreau-yves@sympatico.ca>
Date: 04/28/06-09:44:23 AM Z
Message-id: <0e8b01c66ada$9fa36c20$0100a8c0@BERTHA>

Katharine,

my first reply on this topic was probably the cause of the misunderstanding,
when I read it back now I see what you mean. With the last one I thought I
made all this as clear as I can but I'll try again. If whatever you do back
exposing your print fails to give you a satisfying tonal "delicacy" as you
put it, may be applying a different curve would help.

If I understand normaly exposed gum printing (front exposed) you can control
the distribution of pigment (tonal "delicacy") by the various usual means
including % gum, % pigment, % dichromate, thickness of emultion,
exposure(s), development and physical manipulations, etc. With back
exposure, it seems only one exposure can be done and all I'm saying is that
beside all the usual controls you have the possibility to change the
negative density (distribution) by applying some curve. Can you control
every thing with some curve, the answer is simple no. The reason for this is
that a couple variables of the gum process are totally independent of
exposure (negative densities), the pigment load, as you call it, is one of
these, development and physical manipulations are other mean by which you
can alter the tonal distribution, in the limit you can scrape it all off
(the emultion).

I would certainly claim that if you maintain every variables fix ie. you
don't change anything from print to print except the curve applied to the
negative, you can basically obtain any tone you want between the Dmax and
the Dmin of the print. Obviously, this fix variable gum print must show
something usable to begin with.

Regards
Yves

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@usask.ca>
Sent: Friday, April 28, 2006 9:40 AM
Subject: Re: Back-exposing on plastic (was: Re: Gum transfer

> Then I guess we're all in agreement, as long as Yves isn't claiming
> that the curve can transcend the nature of the gum emulsion, but only
> that a curve can urge a particular emulsion to its full potential,
> whatever that is. Before, it sounded like he was claiming everything
> for the curve, that simply by adjusting the curve, I would be able to
> make that too-contrasty (because too-pigmented or not dichromated
> enough or perhaps both) back-exposed emulsion print a tonal scale
> like carbon. If he's not claiming that, then like I say, we're
> probably all in agreement.
> Katharine
>
>
> On Apr 27, 2006, at 7:14 PM, Christina Z. Anderson wrote:
>
> > I'm 100% with you on this one, Yves.
> > Chris
> >
> > I say, you can still play with the curve of the negative just like
> >
> >> any other variable, that's all I'm saying nothing more nothing less.
> >> Regards
> >> Yves
> >>
> >
> >
> >>> >Katharine Thayer said: Well yeah, somewhat, but the point is
> >>> that a
> >>> >curve isn't going to help if the other variables are off,
> >>> because tonal
> >>> >scale in gum, at least in my experience, is more a function of the
> >>> >emulsiion than of the negative.
> >>>
> >>> Judy Seigel said: My experience also... but I think development
> >>> is a
> >>> real variable, too...
> >>>
> >
> >
> >
Received on Fri Apr 28 09:42:37 2006

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