You might try putting tape on the back side of your metal straight edge.
>
> It is not only Platine. I have recently experienced this problem on several
> papers including Cranes Crest (Platinotype), Simili Japon, Lenox, and
> Platine. And on one print I had a red spot - something I have not seen
> before. Also I recently saw a print on Beinfang by Eric Neilsen with a black
> spot, so its not just that paper.
The print that Keith refers to is part of a print exchange, and yes, it
has a rather obvious black speck in the sky. There seem to be several
different kinds of spots that will appear in prints; The little black
specks, BIG black spots and red spots.
The little black specs I have passed off as impurities in the chemicals
or paper, or both. The BIG black spots, as on the Beinfang print can be
imperfections in the paper that allow the solution to "puddle" on that
spot. And the red spots that I have seen are from the rubber rollers of
the paper making process.
>
> When I last talked to Dick Arentz a couple weeks ago he said that he too had
> been having this problem. The thing that seemed to solve it for him was to
> filter his metal solutions through filter paper from a chemical supply
> store. (Coffee filters are too coarse.) Apparently tiny grains of Pt or Pd
> may precipitate out of solution and embed themselves in the paper. I have
> examined coated sheets to try to find them before printing but with no
> success. Heating the solutions may also help. I hope to check out one or
> both of these ideas this week, time permitting.
>
> Recently Jeff Mathias suggested that substituting a potassium palladium salt
> for the usual sodium palladium salt has eliminated this problem for him.
> Worth looking into.
I would recommend that in place of Potassium palladium salt, one uses
the ammonium palladium salt. The ammonium platinum is more soluable
than the potassium platinum salt, so the effects of the ammonium would
be more beneficial than the potassium salt.
Stephen wrote,
Any guarantees if we buy directly from
> >Martin Axon?
> >
Martin will help if there is a problem, but the paper is as David said,
the same for all of us.
>
-- Eric J. Neilsen 505-758-8868 http://laplaza.org/~ejnasn