[alt-photo] Re: Old buffer
marekmatusz at hotmail.com
Fri Mar 1 17:05:29 GMT 2013
EDTA in the form of Na2EDTA, or other should work well for removing carbonate buffers from paper. It should dissolve insoluble calcium carbonte (or magnesium if present). SOme acidification with citric acid might be helpful, but I am not sure if needed. I meant to try it and compare to HCl soak results on the FA soft press. I might do it this weekend. This acidified FA soft press is great for palladium as I mentioned, but also produces beautiful dark cyanotypes.
Chris, does your stop bath contain EDTA or just citric acid?
> From: christinazanderson at gmail.com
> Date: Fri, 1 Mar 2013 09:04:11 -0700
> To: alt-photo-process-list at lists.altphotolist.org
> Subject: [alt-photo] Re: Old buffer
> I'll add 2¢ to my own words. I cannot use HCL in school with students since our labs are open from 8AM to 10 or 12 at night, in individual labs unsupervised. But if there is anything that has been the bane of my existence, it is this paper alkalinity issue.
> If you see p. 246 there are other options for acidifying.
> The caveat is this: I have read on this list (we had a heated debate a while ago) and from Mike Ware that other acids produce calcium compounds harder to remove than does HCL. Since I am not a chemist I cannot prove that wrong or right, but in school I have been having the students use either stop bath or citric acid (oxalic acid is fine, too) and those have been great for even Fabriano Artistico. This is the first year I have done this, and this new step came about after last year's fiasco of buying a bunch of "great" papers and handing them out to students to find they printed horribly in argyrotype.
> What is the pH of a 5% HCL, anyone know? Etienne, I think you are the one who uses HCL regularly for platinum. Have you measured the pH of it? Here our HCL comes in 37% in gallons at the hardware store as has recently been said in a conversation.
> The question I also have is the long term effects of even citric or oxalic vs. hydrochloric. If all were used at the same dilution, is there a way to tell that one is more harmful?
> This year the Canson papers have been incredible for both VDB and cyanotype, and they are cheap and don't require acid. Canson Montval especially beautiful.
> Christina Z. Anderson
> On Mar 1, 2013, at 6:59 AM, Henry Rattle wrote:
> > Hi All,
> > One of the first major things I've learned from Christina's new book is why
> > my cyanotype prints have been so pale, so often, for more years than I care
> > to admit. I have learned over time to "develop" them in water acidified with
> > acetic acid to about pH 5-6, which helps, but because all the papers I use
> > (Waterford, Bockingford, Artistico) are (as I now understand) heavily
> > buffered, it just seemed to be the way things are.
> > After reading Chris's chapter, I tried some different, cheap (and presumably
> > unbuffered) paper and lo and behold! Deep blues!
> > So - Chris suggests pre-acidifying paper for cyanotype in 5% hydrochloric
> > acid. This seems pretty ferocious - I think it's about pH 1? - so doesn't
> > that damage the paper in other ways? Has anyone found gentler ways of
> > neutralising the buffer in these nice papers?
> > Best wishes
> > Henry
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