RE: bronzing in pt/pd

Different types of metal salts can have different propensities toward
bronzing. I actually ran some step tablet tests a few years ago that proved
this to my satisfaction. The worst in my experience is Lithium palladium when
used as a DOP metal salt. It almost always requires double coating. Ammonium
palladium seems to have the least propensity for this. I have also noticed
(but not tested rigorously) that humidity plays a role. I notice that bronzing
is much more likely when the ambient humidty in my darkroom is below 30% than
when it is closer to 50%. Since I live in Houston, 50% is more the rule than
the exception!

Clay
Quoting Eric Neilsen <e.neilsen@worldnet.att.net>:

> They are directly related but also with the type or mix of coating being
> applied. PD is much more likely to bronze than platinum, but a thin coating
> will do it, I have not seen or do not recall seeing, a well coated print do
> it. You can also see it if you have an imbalance in the coating solution;
> too much ferric for too little metal salts.
>
> Eric Neilsen Photography
> 4101 Commerce Street
> Suite 9
> Dallas, TX 75226
> http://e.neilsen.home.att.net
> http://ericneilsenphotography.com
>
>
> > -----Original Message-----
> > From: Christina Z. Anderson [mailto:zphoto@montana.net]
> > Sent: Thursday, April 06, 2006 9:14 AM
> > To: alt-photo-process-l@usask.ca
> > Subject: Re: bronzing in pt/pd
> >
> > So what y'all are saying, Eric, Don, Jeremy, is it is as much exposure as
> > thin coating, and the thinness just created more of an exposure issue??
> > chris
> >
> >
> > > Chris, If you are having your students coat and print with brush
> > strokes
> > > that show it will be easier to see some on many prints. It is easily
> > done
> > > with the use of a brush; foam or bristle. You can feather the edges of
> > the
> > > overcoated area, that where the neg presumably won't be placed, to allow
> > > for
> > > some very thin areas. If thin were the only the answer you could see it
> > > all
> > > over the place where thin coated areas were present. It also has to do
> > > with
> > > coating solution used. If you are only using PD it will appear more
> > often,
> > > but can happen with PT as well.
> > >
> > > Thinner coatings are faster than thick ones but are also less able to
> > hold
> > > the exposure before bronzing/solarizing (old expression).
> > >
> > > Eric Neilsen Photography
>
>
>

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.