Re: How to super harden papers?

----- Original Message -----
From: "John Cremati" <johnjohnc@core.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, March 26, 2005 3:59 AM
Subject: Re: How to super harden papers?

> Hi Sandy,
> Just some thoughts.
> I know with my little experience in extreme high
> relief , the ph
> is said to be the critical factor in the amount of
> swelling the gelatin is
> able to do.....The maximum swelling is achieved about a PH
> of 8.4 with the
> minimum swelling taking place at about 4.7....... As a
> thought, maybe you
> are coating or attempting to size the paper at or close
> to a maximum
> condition in the wet state...... Then when dried, it has
> not sized the paper
> sufficiently .....
> Possibility the paper reacts with the gelatin
> causing the ph to be
> changed at surface level and again when dry, it does not
> have the amount
> of gelatin size necessary to do its job.................
> Another thought is the pigmented emulsion at a ph
> of 8.7 causing
> high relief in the wet state but low relief when
> dried.....Maybe as a
> experiment I would try coating the paper using a PH
> emulsion opposite of
> what you are using to see what you may see .
> Please let me know of your progress.
>
> John Cremati
>
   Are you sure that maximum swelling occurs at pH 8.4? It
seems to me that swelling continues to increase on either
side of the isoelectric point of the gelatin. Also, pH 4.7
seems to me rather too low for photographic gelatin as found
in printing paper although it might be right for the gelatin
used to make carbon tissue.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com