Sizing paper with gum and dichromate, was Re: glut

Loris, Yves and others,

I tried gum sizing too and got the same greenish stain that would not
clear even after a long(er) disulfite bath and wash. Probably I
overexposed. But why not standardize things a little bit more and size
with gum and expose with your standard printing time through a clear
sheet of printing substrate (or film). I'll give that a try this week. I
do like my gelatin/formalin or gelatin/glyoxal sized papers but there's
allways a different 'feel' in the first (gum on gelatin) and the
subsequent (gum on gum) coats.

-kees

Loris Medici wrote:

>IME, the practice of sizing with gum has the risk of dichromate staining
>unless you expose very carefully. When I coat the paper with unpigmented
>gum + dichromate mixture and expose it 30 secs without the negative +
>contact printing frame combo (my normal exposure with negative and
>contact printing frame is 360 secs / 6 mins. In other words: I expose
>the unpigmented gum + dichromate mixture ~ 3.5 stops less when
>sizing...), I get a slightly greenish / grayish surface (very slight and
>subtle, but you can see it clearly), not paper white. Probably I should
>expose less in order to get rid of the stain (or reduce it further) but
>if I do so, I may get suspicious about the effectiveness of the sizing.
>Therefore, I size with gelatine and harden in formalin. (BTW, I should
>admit that: I never tried to use paper sized in that manner - I mean for
>gum printing, I didn't like the cyanotypes I've made on paper sized with
>gum dichromate - and dumped that method when I saw the stain + my bad
>experience with Cyanotype... I also didn't tried to establish a
>non-staining exposure time - I guess I was lazy back then).
>
>Regards,
>Loris.
>
>-----Original Message-----
>From: Yves Gauvreau [mailto:gauvreau-yves@sympatico.ca]
>Sent: 15 Aralık 2005 Perşembe 14:31
>To: alt-photo-process-l@sask.usask.ca
>Subject: Re: glut
>
>
>Hi,
>
>out of curiosity, would there be a "problem" sizing with gum instead of
>gelatine especially if you intend to do gum printing later???
>
>Yves
>
>PS Aren't we suppose to sent our message in plain text...
>
>
>
Received on Thu Dec 15 08:27:35 2005