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Re: Specks on Specks on my Z--types



> jason plunkett wrote:
> ... noticed a problem recently with
> black specks that show up during the coating of the paper.  I am
> coating Crane's Platinotype White with a rod using only Ammonium
> Ferric Oxalate and Lithium Palladium. 

First and foremost, the Z--type is only a POP Pt/Pd print which unjustly
takes advantage and profiteers from the Zia name.

As Carl Weese mentioned the dark blotches observed by candling should be
avoided.  Candle and coat only on the clear portions of a paper.  And,
any metal fragments such as may come from paper cutting should be
avoided.  Use a mat cutter which cuts with a single razor blade without
rubbing against other metal.

As for the problem of a too saturated solution, also mentioned by Carl,
the remedy is to warm the solution.  If kept in a closed dropper bottle,
evaporation should not be an influence.  Do not simply dilute the
solution as this may result in not enough metal being used.  By the way,
the solution strengths called for in the New Platinum Print are not
correct and will likely produce slightly weaker prints (there are also
many other factors influencing the amount of metal in the coating). 
Information on solution strengths, metal in the coating, and a method to
determine if they are optimized can be found in my guide (from link at
bottom of post).  If the temperature of the solutions is lowered enough,
crystals may precipitate from almost any strength solution.  However, it
is also likely that any crystal chunk in the coating will be washed away
by the clearing and washing.

Contrary to Robert Lyman, specks are not as common a problem as he may
suggest.  I do not know what Robert is referring to by "plating out
during coating", perhaps he can elaborate.  However, his suggestion as
to cleaning the coating equipment is highly important.

Another way specks may appear in the print is with a high temperature
with sodium and platinum salt present, but this is not your case.  In
such situations, use salts other than sodium.

Another way for stray metal to get onto a coating may be from an old
corroding air/hair blower used to dry the coating.  Blow it into a clean
cheese cloth to see if it is blowing crud around.

Since you are noticing the specks during coating and are using a rod,
another problem may be a scratching of the paper surface caused by the
rod scraping the speck along the surface.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/