From: Eric Neilsen (e.neilsen@worldnet.att.net)
Date: 12/28/00-08:22:57 PM Z
Judy Seigel wrote:
>
> 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
I have tried to use the term Coating Solution when referring
to platinum printing, Kallitype, Van Dyke, Cyanotype, etc.,
where the liquid is clear and emulsions for Gum, liquid
Light, etc., where the light sensitive material is held in
suspension via an additional ingredient.
EJ Neilsen
-- Eric J. Neilsen 4101 Commerce Street, Suite #9 Dallas, TX 75226 214-827-8301 http://e.neilsen.home.att.net http://www.ericneilsenphotography.com
This archive was generated by hypermail 2b30 : 01/03/01-03:59:42 PM Z CST