[alt-photo] Re: dilution of pt/pd - water in the brush

[EJ Photo]

Loris, 

While the figures you are quoting are for nearly .5 molar solutions, I make
mine to a nearly .7M solution. Make my own ferric to liquid at a stronger
solution than 28% +/- to a solution of approx 35%. Independent test confirm
faster and better blacks with my mixtures than those from B&S. 

In Ware's paper from the late 80's or early 90's, he using a .7M target for
metals and 1.4M for AFO. 

I'd like to point out another source of dilution and that is water in the
brush or coating device. It all adds up to a technique. That is the bottom
line and I say that time and time again. You can't look at just the solution
strength without the whole process. The balance of the FO/AFO to metals is
important and is the starting point at the coating level.
 


Eric Neilsen
Eric Neilsen Photography
4101 Commerce Street, Suite 9
Dallas, TX 75226
 
www.ericneilsenphotography.com
skype me with ejprinter
www.ericneilsenphotography.com/forum1
Let's Talk Photography
 
-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
Loris Medici
Sent: Friday, July 23, 2010 2:13 AM
To: 'The alternative photographic processes mailing list'
Subject: [alt-photo] Re: dilution of pt/pd

BTW, let's check it:

Na2PtCl4 =  382.87g / mole, therefore:
200g (in 1000ml 20% solution) / 382.87g (1 mole) ~=  0.52M, which is
slightly stronger (~ 2% in molar terms) than your 0.51M Na2PdCl4 solution...

So, 15% Na2PdCl4 is "approx." molar equivalent to 20% Na2PtCl4 and vice
versa.

Regards,
Loris.


-----Original Message-----
From: Loris Medici
Sent: Friday, July 23, 2010 9:41 AM
To: 'The alternative photographic processes mailing list'
Subject: RE: [alt-photo] Re: dilution of pt/pd

...

> Interesting, too, that even though my PT is referred to as a "20%" (10/50)
it is actually only 15%.

No, your Pt is indeed 20% if you're using B&S Pt Soln. #3...

Now, the reason for a stronger Pt soln. could be due the fact that it has
less covering power compared to Pd... I'd definitely opt to extend the
solution with water (in order to facilitate coating), instead of using extra
"precious" noble metal "which - theoretically, won't have the chance of
being reduced!"

Regards,
Loris.

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