Re: clearing dichro stain with sulphuric acid was Re: (Gum) Tonal scale

Loris,

yes, this is exactly my point, we add more and more stuff but where does it
go?? I'm sure you can't wash it all out and it stays in the paper.

Yves

----- Original Message -----
From: "Loris Medici" <loris_medici@mynet.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, December 09, 2005 9:57 AM
Subject: RE: clearing dichro stain with sulphuric acid was Re: (Gum) Tonal
scale

I would be more worried about the long-term effect of sulfuric acid on
paper's fibers. (Probably this is a higher risk factor when compared to
minute amnt. of residual reduced chromium.)

Regards,
Loris.

-----Original Message-----
From: Yves Gauvreau [mailto:gauvreau-yves@sympatico.ca]
Sent: 09 Aralık 2005 Cuma 16:36
To: alt-photo-process-l@sask.usask.ca
Subject: Re: clearing dichro stain with sulphuric acid was Re: (Gum)
Tonal scale

Thanks Pete,

I should have said it earlier, I search the archive and I have found
that tests where made (by you maybe) and showed sulphuric acid clearing
to have only 0.05 residual density and as you say below some light grey
tint is left.

All this makes me wonder how all of these invisible little molecules
will affect the permanence and stability of gum prints... There getting
farther and farther from those cavern paintings every time I think about
it.

Regards
Yves

----- Original Message -----
From: "peter" <temperaprint@blueyonder.co.uk>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, December 09, 2005 8:24 AM
Subject: Re: clearing dichro stain with sulphuric acid was Re: (Gum)
Tonal scale

> Yves,
>
> I think there is always a stain, The stain left by the sulphuric acid
> is not heavy is but a light grey in colour you will need to have a
> heavy brown oxidised stain intialy to be aware of it.I find it very
> useful in maintaing Tricolour balance
>
> Pete back from he
>
>
>
>
>
>
>
> On 7 Dec 2005, at 09:23, Yves Gauvreau wrote:
>
> > Pete et all,
> >
> > I don't know if you saw Katharine experiment (link below) or not but

> > the reason I ask the question was to find out if the one(1%)
> > solution of sulphuric acid you've been using all these years would
> > leave a noticable
> > tone like the NaCl and the other stuff did leave???
> >
> > Yves
> >
> >
> > ----- Original Message -----
> > From: "peter" <temperaprint@blueyonder.co.uk>
> > To: <alt-photo-process-l@sask.usask.ca>
> > Sent: Tuesday, December 06, 2005 9:35 AM
> > Subject: Re: (Gum) Tonal scale
> >
> >
> >> Dear Yves.
> >>
> >> I have used a one(1%) solution of sulphuric acid to clear the brown

> >> dichro stain for the past twenty years with no ill effect in both
> >> Gum and Temperaprint.
> >>
> >> Best wishes
> >>
> >> Pete
Received on Fri Dec 9 09:59:31 2005