From: Katharine Thayer (kthayer@pacifier.com)
Date: 07/16/03-04:29:49 AM Z
Hi Bill,
My guess is that the gum in these particular images may not have been
really hardened in the first place, possibly due to underexposure, and
it dissolved when re-wetted. A properly hardened gum image should not
dissolve when put back in water, with or without clearing compound in
it.
According to some experts, potassium metabisulfite is the gentlest of
the potential clearing solutions available, and sodium bisulfite is the
harshest. I can't comment on that assertion because I have needed to
clear very few of the hundreds of gum prints I've made over the years,
and the only clearing solution I've ever used is sodium bisulfite. But
I'm willing to take others' word in this case, and I've never seen
sodium bisulfite lift an image off the paper, so it stands to reason
that potassium metabisulfite would be even less likely to do so. That's
a longwinded way of saying I don't think it's the potassium
metabisulfite that's the problem, as long as it's properly mixed, and
you've made sure of that.
That's no help for the images that are lost, I'm sorry.
Katharine
The Painted Horse wrote:
>
> Hi Cris, Katharine, and everyone else.
> So, I left the my gum image in the Montana, noon day sun. After two
> hours there was definite fading but not total clearing of the image.
> I'm sure if I would leave it out more it would clear, and I intended to,
> but a disaster took me off in another direction and I could use some
> help. While testing the sun clearing of gummed images I was working on
> another print clearing with pot metabi (3 tblspns per litre). When I
> went to clear, the image began to lift and wash away! And this only
> after 1 minute of clearing.
>
> I thought I mixed the pot metabi incorrectly so I started over with
> another print waiting to be cleared...same results. Now, I have two
> prints in the trash and I'm afraid to try and clear another print for
> fear of losing more work. The strange thing is I already cleared one
> print for over 5 minutes in the pot metabi a few days earlier with no
> problems. Do you need to mix the pot metabi and let it stand for a
> while? I mixed this batch and used it immediately. I could try the pot
> metabi at 1% so it isn't as aggressive, but thought I would get some
> input from the list before I move forward.
> Thanks.
>
> Bill-
>
> Katharine Thayer wrote:
> >
> > Christina Z. Anderson wrote:
> > >
> >
> > >
> > > So you could actually just duplicate this with test strips exposed under
> > > plain dichromate--my exposures were UV BL 5 minutes.
> > > Chris
> >
> > Okay, the sun came out, and I've got a test going. I tried to stick with
> > replicating your results as above for now, with one change. I used
> > saturated dichromates, but rather than giving them the same exposure, I
> > tried to expose them so the dichromate stain in the borders (I made
> > really big borders) was the same shade of brown on both. Unfortunately I
> > missed and exposed the ammonium too long, even though its exposure was
> > significantly shorter than the time for the potassium. So the ammonium
> > dichromate stain is a bit darker than the potassium dichromate stain
> > and so any difference I see in result between the dichromates will be
> > uninterpretable. At any rate this is really just a quick and dirty test
> > anyway to see if I can get the same bleaching you got, even with the
> > potassium.
> >
> > Too sick to do more than this today; I'll report back with my results,
> > hopefully before you've left for APIS.
> > kt
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