Re: printing out paper

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From: Robert W. Schramm (schrammrus@hotmail.com)
Date: 12/28/00-08:41:06 PM Z

Judy et al,

Well, I am not a chemist but I remember some of it from college courses. In a solution you have a solvent in which something is dissolved. This solute actually combines with the solvent. For example, if you dissolve salt NaCl in water you get a saline solution in which there are sodium and chlorine ions. In an emulsion one substence is suspended in the other. The two substences do not interact but retain their own properties. Oil and water, for example, do not ordinarily mix but you can create an emulsion (read suspension) of oil in water by breaking it up into fine droplets. Mayonaise is a good example of an oil-watrer emulsion.

BTW, and on another subject. The sky was clear here on the 25th and we got a great view of the eclipse. How about you? Don't throw the glasses away as you can use them for the next eclipse. However, I can think of no use for old Moon Pies. ;-)

Bob Schramm

>From: Judy Seigel
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: alt-photo-process-l@sask.usask.ca
>Subject: Re: printing out paper
>Date: Thu, 28 Dec 2000 14:34:09 -0500 (EST)
>
>
>
>On Wed, 27 Dec 2000, Sarah Van Keuren wrote:
> > ....A distinction I make that Judy may not make is between
> > an emulsion and a chemical solution. P.O.P. with silver chloride salts in a
> > gelatin coating is for me an emulsion. Gum bichromate with pigment suspended
> > in sensitized gum arabic is also an emulsion. The trick with syrupy
> > emulsions is to attach them to the support but to keep them on the surface
> > of it. Cyanotype, vandyke, palladium, platinum and ziatype are all chemical
> > solutions, watery mixes that soak into the fiber of the paper....
>
>Sarah, you forced me to get up from this chair & consult dictionary, which
>after "a milky fluid made by rubbing almonds with water" gives, for
>emulsion, "an intimate mixture of two incompletely miscible liquids" -- by
>which definition it sounds like you're right -- gum and silver salts in
>gelatin may very well be emulsions, the others (sound like) solutions.
>
>Of course as several "alt" books (now lost in mists of time -- maybe KOL?)
>point out, people CALL them emulsions, & many (most?) of us have the
>habit. Maybe our usage has even changed the meaning -- as language does
>change.
>
>But maybe we *should* stress the distinction as you suggest... the
>difference between sinking into the paper (cyano, etc.) and sitting on it
>(gum, etc.) surely affects coating, developing, clearing, etc.
>
> > ....I think it
> > helps those who are learning alternative processes to understand this
> > distinction. Does anyone else find this a helpful distinction?
>
>Of course some of those "emulsions" may do some of each (???), but the
>point is well taken, the distinction may deserve more attention than it's
>had. On the other hand, *making* that distinction gives us teachers ways
>to make even MORE mistakes than we do already (a dangerous profession).
>
>best,
>
>Judy
>
>

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