Re: Eliminating CaCO3 in buffer in "achival" watercolor papers
Forgot to write that I also plan to clear the paper in Sodium Sulfite after soaking it in HCl to soften the fibers in order to eliminate the remaining CaCl2 and HCl (+ a final plain water rinse, maybe 3 - 4 changes...) Do you think this is a nice addition to the procedure? Or is it totally unnecessary and/or harmful (due reaction products of CaCl / HCl / Sulfite...)? Thanks again, Loris. 12 Ağustos 2008, Salı, 9:01 am tarihinde, Loris Medici yazmış: > Hi all, this question goes to chemists and/or papermakers especially: > > Albeit I like COT 320 for iron based alternative processes (such as > Cyanotype, Vandyke / Kallitype, Pt/Pd...), I have to import this paper and > cost is high. I can find nice Fabriano Artistico (Trad. White) paper at > good prices locally; the distributor is running an aggressive pricing > policy due to competition + they're very helpful / willing to bring > (not-much-sought-by-watercolor-artists) smooth HP papers just for me. > > Anyway, this paper incorporates a CaCO3 alkali buffer (hence the > designation "archival") which is fatal to iron processes. I tried to > neutralize the paper with Oxalic Acid before and it was a disaster. IMO, > Oxalic Acid is not a good way to go since CaCO3 + Oxalic Acid forms > unsoluble compound Calcium Oxalate (kidney stones!) which crystals are > very sharp and a) makes the surface gritty (very strong effect with > Artistico), b) sharp crystals will eventually cut the paper's fibers and > weaken it (due to movement in development / rinse stages and when handling > later)... > > I was searching for a highly soluble Ca compound and found it to be CaCl2 > (Calcium Chloride). To get CaCl2 from CaCO3, you have to react it with HCl > (Hydrochloric Acid)(other byproducts are CO2 and water) HCl too is harmful > to paper fibers (may lead to yellowing and brittle the paper later...) but > I know that it was used (and maybe still used) by Pt/Pd printers as a > clearing agent. > > So, I need ballpark figures (to start testing) for strenght (of HCl > solution) and lenght of reaction (soak time) in order to get rid of CaCO3 > in Artistico paper which is not harmful to the paper. Can you make > suggestions? I plan to use 1% HCl and soak the paper in it for 5 minutes. > Is that too long/short and/or do you think I should use a milder/stronger > HCl strenght? I know this depends much on paper (how much CaCO3 it > contains ect.) > > What do you think? Is that a good / sound way to go? Any other > suggestions? > > Thanks in advance, > Loris. > > >
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