RE: Ferric Oxalate or Ferric Ammonium Oxalate
My head hurts :)
Thanks for sharing that information, Loris. Fascinating stuff.
On Fri, November 3, 2006 3:07 pm, Loris Medici wrote:
> Hi Sandy, I'm not familiar with the Ammonium salt since I use the Lithium
> salt. As far as I understand from Mike's practical instructions the Ammium
> salt and the AFO sensitizer is what you need to do Ware-Malde POP process.
> Let me highlight some information from Mike's article:
> (URL: http://www.mikeware.co.uk/mikeware/Platino-Palladiotype.html)
> "... The printing exposure range (logH) values in Table 2 indicate the
> effects of these controls. We do not recommend the addition of oxidising
> agents, such as potassium chlorate, potassium dichromate or hydrogen
> peroxide to the sensitizer, as employed in the traditional method for
> contrast control, because the effect of these is not to uniformly contract
> the tonal scale, but simply to truncate the high values.
> If humidity control seems too bothersome, then the most consistent results
> can be obtained at normal UK ambient RH (40-70%) by mixing the platinum
> palladium solutions in the ratio of about 3:1, respectively; this
> has a contrast and speed that are fairly constant over wide variations in
> humidity and it yields a long range of well-graduated neutral tones and a
> good Dmax..."
> Please note that the Pt is not the usual Potassium salt, it's the Ammonium
> salt. I think you can use the K salt if you like to (adjusting the
> strength so that molarity is the same). My understanding is that Mike
> doesn't like K salts because it may cause forming of Potassium Oxalate
> is insoluble, therefore will cause a gritty sensitizer... But since the
> amnt. of KPt salt will be 1/3rd of what you need for pure Pt printing, the
> negative effect of using the Potassium salt may not be that pronounced ->
> worth to try in my opinion.
> As you can see Mike doesn't favor addition of oxidisers for contrast
> control. My experience with Ziatype (Li salt variant) is that addition of
> Ammonium Dichromate definitely increases the contrast of the emulsion and
> a very effective contrast control tool - and it shows no graining,
> / tones remain smooth...
> Anyway, I would suggest that you contact Mike directly for further and
> detailed information. I'm sure he'll provide you the best advices you can
> possibly have ;)
> BTW, I don't think you strictly have to control the printout during the
> exposure, at least if you use the Li salt... Since Li is very hygroscopic,
> fair amnt. of humidity will remain inside the coating even if it looks
> surface dry. I just follow the same drying protocol (5 minutes laying flat
> on the coating table + 5 to 10 minutes blowing cold air to the paper which
> is tacked to the wall - bent slightly so that air can circulate both in
> front and back of it for more uniform drying) to maintain consistency. %90
> of the time I just start to clear the paper without further exposure -
> exposing it for my SPT I mean... In other words, I'd say it's perfectly
> doable with a vacuum frame.
> Hope this helps!
> Best regards,
> From: Sandy King [mailto:firstname.lastname@example.org]
> Sent: 03 Kasım 2006 Cuma 17:55
> To: email@example.com
> Subject: RE: Ferric Oxalate or Ferric Ammonium Oxalate
> I have Palladium II Chloride powder on hand. Looking at Mike Ware's
> directions, it appears that I can prepare Ammonium
> by mising ammonium chloride with palladum II chrloride. Would this be all
> need, along with the FAO, to give Ware's POP method a try? In other
> can a basic sensitizer be made with just Ammonium
> and Ammonium Ferric Oxalate, or do I need something else?
> Also Is it possible to control contrast with the Ware method with
> dichromate? I would rather do this than attempt to do so by varying RH?