RE: Dark reaction in dichromated colloids

From: Kate Mahoney ^lt;kateb@paradise.net.nz>
Date: 06/14/04-03:29:31 PM Z
Message-id: <001301c45256$ae8da500$2726f6d2@ratbag>

Hmmm....interesting - most commercial preparations say "do not freeze".
Perhaps thatís because the freeaing needs to be done in a controlled
way.
BTW I'm becoming interested in making my own silver emulsion - anyone
got a good recipe, technical hints?? The only recipe I've got is in a
1908 Photographer's dictionary and it looks very very very complex -
surely there is a "kinder, gentler" way????
Cheers
Kate

Kate Mahoney Photography

-----Original Message-----
From: MARTINM [mailto:martinm@SoftHome.net]
Sent: Monday, 14 June 2004 6:04 p.m.
To: alt-photo-process-l@sask.usask.ca
Subject: Re: Dark reaction in dichromated colloids

"Yes, gelatine can't be frozen in foodstuff applications so I don't
think
it could be frozen in photography - I think that's why you can't freeze
> liquid silver emulsion to keep it longer."

Certain methods to enhance silver concentration (in
silver halide emulsions) are based on "freezing and thawing". The frozen
emulsion is remelted and coated.
Freezing allows the removal of 90% water and hence increase the silver
halide/gelatin ratio.

Martin

----- Original Message -----
From: "Kate Mahoney" <kateb@paradise.net.nz>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, June 13, 2004 12:31 AM
Subject: RE: Dark reaction in dichromated colloids

> Yes, gelatine can't be frozen in foodstuff applications so I don't
think
> it could be frozen in photography - I think that's why you can't
freeze
> liquid silver emulsion to keep it longer. I have (inadvertently)
frozen
> gelatine and think it destroys the cell capsules, causing it to break
> down into a sludge....
> Kate
>
> Kate Mahoney Photography
>
>
> -----Original Message-----
> From: Katharine Thayer [mailto:kthayer@pacifier.com]
> Sent: Saturday, 12 June 2004 11:32 p.m.
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: Dark reaction in dichromated colloids
>
> Ender100@aol.com wrote:
> >
> > What happens if you freeze it?
> >
>
> According to Kosar, the Lithographic Technical Foundation "reported
that
> the thermal reaction on dichromated-albumin and dichromated-gum arabic
> deep-etch plates can almost be stopped when the plates are stored at
38
> degrees F (3.3 degrees C) and 72% relative humidity. However, a small
> drop in gamma can be expected after sensitized materials have been
> stored at low temperature for a prolonged period." This isn't
freezing,
> but it's close. I have a feeling freezing wouldn't work for most
> colloids; I'm thinking from my experience freezing jello by mistake
> once (I was trying to chill it in a hurry and left it too long).
> kt
>
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Received on Mon Jun 14 15:29:54 2004

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