RE: Watercolor pigments - pigments to avoid...

Hi Katherine,

I agree (and it makes sense) that if the paper is sized with gelatin, then
the higher your gelatin bath is, the more likely it is going to cause
trouble.

You can use gelatin bath with a more controlled temperature, as you did, or
maybe you can try hardening the paper itself first (more accurately,
hardening the internal sizing of the paper first). Then when you add
external sizing yourself, the temperature is less critical. I don't know
whether it will work, and I don't know which one is actually easier (for me,
I think sizing all the paper once, perhaps after purchase, doesn't seem to
bad), but it might be worth a try to see if it works and/or to gain some
insight to the internal sizing.

Dave

PS: I still cannot make any gum print right now. I am hoping to move to a
new place this summer, but currently I am only in the process of searching
for the new place....

> -----Original Message-----
> From: Katharine Thayer [mailto:kthayer@pacifier.com]
> Sent: Thursday, July 13, 2006 11:34 AM
> To: alt-photo-process-l@usask.ca
> Subject: Re: Watercolor pigments - pigments to avoid...
>
>
> On Jul 13, 2006, at 7:59 AM, Christina Z. Anderson wrote:
>
> >> You heated the gelatine to a point where you destroyed its
> qualities
> >> as a size..
> >> Forget the formalin.
> >> Terry
> >>
> >
> > Terry,
> > I respectfully disagree. I know this isn't good practice, but to
> > prove a point I boiled my gelatin and lived to tell the tale. Even
> > gelatin boiled for 20 minutes worked fine as a size on
> about 60 large
> > gums. No speckle, no stain, no nuttin'. For me, this was another
> > myth down the drain that you had to watch the temp of gelatin while
> > heating it up. Or, at the very least, I don't sit there with a
> > thermometer anymore watching the pot not boil. But, as they say,
> > YRMV.
>
> And my own tests show something different from what either of
> you are saying, I think... my own tests show that it doesn't
> matter if the gelatin has been boiled, as long as it's
> relatively cool when it's applied, and furthermore applying
> the size while hot may only be a problem with some papers.
> Arches papers, which are internally sized in a gelatin bath,
> go speckly on coating with gum if the temperature
> of the sizing was over 140 when applied, IME. But if the same too-
> warm gelatin is cooled to 140 and then applied, no speckles
> happen. I suppose that what happens is that the too-warm size
> partially melts and disrupts the internal sizing, affecting
> the behavior of the
> paper. I haven't tried this with papers sized with non-gelatin
> material, but from reports that it's not a problem with such
> papers, I am willing to tentatively conclude that this isn't
> a universal problem, but only affects some papers, most
> likely those with a factory gelatin size.
> Katharine
>
>
Received on 07/13/06-10:02:26 AM Z