U of S | Mailing List Archive | alt-photo-process-l | RE: ferri sesquichlorati

RE: ferri sesquichlorati

The problem that often arises when one attempts more than 8 layers is a
"warping" effect caused by more gum sitting in the shadows than in the
highlights.   As the shadows areas build in density with each coat,
surrounding highlight areas continue to clear.  The shadow areas begin to
appear on the dried print as shiny, lumpy islands of gum that warp the
surface of the paper.


-----Original Message-----
From: Kees Brandenburg [mailto:ctb@zeelandnet.nl]
Sent: Sunday, October 22, 2006 9:00 AM
To: alt-photo-process-l@usask.ca
Subject: Re: ferri sesquichlorati

On 22-okt-06, at 16:06, Halvor Bjørngård wrote:
> BTW, Is there a maximum number of layers for gum, one book I have claim
> twelve or so, but have seen other claims of 20 .. ?

Hi Halvor,

The maximum number of layers is related to the strenght of the (rigid)
package of gumlayers and the constantly expanding and shrinking paper
fibers between wet and dry. I think 20 layersare way too much and only
possible on a rigid (non paper) surface or on a paper that is made
rigid by fixing it on a rigid surface.

My still workable (= near maximum) number of layers is 6 or maybe 7,
but I try to do with less.

I also am very much interested in the 'ferric' hardening of gum
especially from a environmental viewpoint. I'll do some experimenting