Re: Blue stain with carbros-was Clearing Gum Dichromates
s carl king (sanking@hubcap.clemson.edu)
Sat, 13 Jan 1996 12:03:25 -0500 (EST)
>
>
>
> On Sat, 13 Jan 1996, s carl king wrote:
> > Another thing I have observed is that you must renew sodium bisulfite
> > on a regular basis. If old or exhausted sodium bisulfite is used
> > to clear papers it will stain the paper blue. This has happened to me
> > with both Fabriano and Rives papers hardened with chrome alum, and
> > I believe (though not positive) also with formalin.
>
> As noted, gum printing is very different from carbon
> printing, but I will mention that I have re-used sodium bisulfite until we
> were both old & exhausted (at which point it did exactly nothing
> clearing-wise) & have not seen blue stain -- the paper being either not
> sized extra or hardened with formaline/glyoxal.
>
> Judy
>
Actually, this has only happened to me with carbros, but the stain was
over all of the sized and hardened gelatin, not just the image, so
I assumed it not specific to the process. Since there seems to be
no other confirmation of this stain I am now beginning to suspect that
it results either from the chrome alum hardening of the sized gelatin,
which I suspect very few people use anymore, or perhaps some chemicals
left in the image from the carbro chemistry. In any even, sodium
bisulfite is relatively inexpensive and I have learned to avoid the
problem.
Sandy