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 > and > palladium solutions in the ratio of about 3:1, respectively; this > sensitizer > 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 > solution > 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 > which > 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 > is > a very effective contrast control tool - and it shows no graining, > gradation > / tones remain smooth... > > Anyway, I would suggest that you contact Mike directly for further and > more > 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, > a > 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 - > after > 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, > Loris. > ________________________________ > > From: Sandy King [mailto:sanking@clemson.edu] > Sent: 03 Kasım 2006 Cuma 17:55 > To: alt-photo-process-l@usask.ca > Subject: RE: Ferric Oxalate or Ferric Ammonium Oxalate > > Loris, > > > I have Palladium II Chloride powder on hand. Looking at Mike Ware's > directions, it appears that I can prepare Ammonium > Tetrachloropalladate(II) > by mising ammonium chloride with palladum II chrloride. Would this be all > I > need, along with the FAO, to give Ware's POP method a try? In other > words, > can a basic sensitizer be made with just Ammonium > Tetrachloropalladate(II) > 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? > > > Sandy > > Camden Hardy camden[at]hardyphotography[dot]net http://www.hardyphotography.net
|