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  1. #21

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    An educated guess would be: the binder for oil painting (linseed oil - which is very rich in omega-3, 6 and 9 fatty "acids") is protecting the Prussian blue... (Maybe it neutralizes the alkali before it starts to harm the pigment?!)

    Regards,
    Loris.

    Quote Originally Posted by Marco B View Post
    ...Still makes me wonder how they achieve the highly stable nature in modern oil paints, because the artist quality paint that I have lying around ("Rembrand 508" which does use the official PB27 Prussian Blue pigment) is marked as highly stable (three pluss's), which should guarantee centuries of life time if properly used...

  2. #22

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    Quote Originally Posted by Loris Medici View Post
    Katharine,

    This shows us nothing related to our subject (Cyanotypes). You should repeat this with a Cyanotype (or with pure Prussian Blue pigment). Your test may show us either that

    a) Your ammonia is off (Somehow! I think this is unlikely - unless you have anosmia and can't tell if it smells or not...)

    b) There are compounds [in binder / plasticiser / additive ect. in water color paint and/or hardened gum] which are protecting the pigment from alkaline hydrolysis.

    Loris, I know this isn't directly related to cyanotypes; that's why I used the title "Prussian blue pigment and ammonia," why I quoted Marco's question directly, and why I addressed Marco specifically, so as to make clear that I was responding to Marco's question, not to the OP. My test was not intended or assumed to support or disconfirm theory or observations about alkaline fading of cyanotypes.

    Marco's question was about Prussian blue pigment as used in paints, and as I said to him, my answer was only about watercolor paints not about oil paints, but I was curious, and that was what I found.

    The ammonia was fresh and quite odorous.

    Whether using powdered pigment would be a better test of the action of an alkali on pure PB 27 is a good question, but that wouldn't have addressed Marco's question about the pigment as used in paint.
    Regards, Katharine

  3. #23

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    Quote Originally Posted by Marco B View Post

    Still makes me wonder how they achieve the highly stable nature in modern oil paints, because the artist quality paint that I have lying around ("Rembrand 508" which does use the official PB27 Prussian Blue pigment) is marked as highly stable (three pluss's), which should guarantee centuries of life time if properly used...
    Hi Marco again,
    As I said before, I know the pigment only as it is used in watercolor paints, (and by the way, the pigment I used in my test was also PB 27; when Loris suggested that my test would be more relevant if I had used "pure Prussian blue" I think he meant that one should use the pure powdered pigment rather than a paint which will contain other material besides the pigment and medium, not that he thought I wasn't actually using PB 27, which of course I was).

    As I said in that first post, in watercolor paint the stability of the pigment varies widely across brands, and it's possible that in oil paint it may be the same. Prussian blue in three watercolor brands is rated extremely stable and in a few brands is so fadeprone as to be considered fugitive. My understanding from my reading in the past is that the difference in stability of different brands may have more to do with additives and fillers than with the medium itself; lower quality paints sometimes use a calcium carbonate filler to extend the pigment, which might have a deleterious effect on the pigment.

    While we're looking at interesting facts about Prussian blue pigment, I came across some information on the U.S. Food and Drug Administration website that said Prussian blue has been approved as a drug to counteract the effects of radiation poisoning. I didn't save the URL, but if anyone's interested they could no doubt find it by googling the FDA and Prussian blue.
    Katharine
    Last edited by Katharine Thayer; 08-17-2007 at 11:30 AM. Click to view previous post history. Reason: clarity

  4. #24
    rwyoung's Avatar
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    [QUOTE
    While we're looking at interesting facts about Prussian blue pigment, I came across some information on the U.S. Food and Drug Administration website that said Prussian blue has been approved as a drug to counteract the effects of radiation poisoning. I didn't save the URL, but if anyone's interested they could no doubt find it by googling the FDA and Prussian blue.
    Katharine[/QUOTE]

    Legend has it that some of the countryside in the path of the radiation cloud from Chernoybl was treated with Prussian Blue to lock up the radioactive elements... Don't know if that is true (in part or in whole) but it must have looked funky!
    Don't sweat the petty things and don't pet the sweaty things! http://rwyoung.wordpress.com

  5. #25
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    Quote Originally Posted by Marco B View Post
    And two other strange articles regarding Prussian Blue. It seems there is even a "darker site" to Prussian Blue and cyanotype, the first article will certainly make me look different to cyanotypes the next time

    * "Expert Report About the Formation and Detectablility
    of Cyanide Compounds in the ‘Gas Chambers’ of Auschwitz"

    Chapter two is called "Formation and Stability of Prussian Blue"...
    Marco, this is a bit off topic, but you've quoted a report from Germar Rudolf, who is probably the most infamous of all Holocaust deniers, who was trying to disprove the presence of cyanide salt residue in the gas chambers. So, I'd hardly put any credence into his "science", which is appropriated highly selectively for him to prove an agenda.



    Back to topic... Everyone here who argues about the instability of iron blue toners seems to neglect that they impart the same Prussian blue salt as in cyanotypes. I'd think, actually, that the blue-toned prints might be more stable than cyanotypes, because at least during stop bath and fixing you're impregnating the image with an acid. That's not necessarily something you do with any cyanotype.
    Paul

  6. #26

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    Quote Originally Posted by DrPablo View Post
    Back to topic... Everyone here who argues about the instability of iron blue toners seems to neglect that they impart the same Prussian blue salt as in cyanotypes. I'd think, actually, that the blue-toned prints might be more stable than cyanotypes, because at least during stop bath and fixing you're impregnating the image with an acid. That's not necessarily something you do with any cyanotype.
    It was my impression that the reputed instability of prints toned with iron blue toner may have to do not with the instability of Prussian blue itself, but with the presence of silver ferrocyanide that hasn't been converted to Prussian blue and hasn't been fixed. See

    http://www.unblinkingeye.com/Articles/Blue/blue.html
    kt

  7. #27
    Marco B's Avatar
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    Quote Originally Posted by DrPablo View Post
    Marco, this is a bit off topic, but you've quoted a report from Germar Rudolf, who is probably the most infamous of all Holocaust deniers, who was trying to disprove the presence of cyanide salt residue in the gas chambers. So, I'd hardly put any credence into his "science", which is appropriated highly selectively for him to prove an agenda.
    Hmmmmm, I'm very,very sorry , I certainly had no intention of quoting any such infamous character...

    Unfortunately, I am not able to edit this post anymore, and remove the quote... Maybe a site or forum administrator could do that...

    Google turned up the result when I searched for some keywords as "stability" "prussian blue" , and although I had a quick look through the article, the 70 pages or so was a bit much and did not immediately raise my suspicion, as it should have~!!!

    Thanks for the useful - and necessary - history lesson... !
    Last edited by Marco B; 08-17-2007 at 12:30 PM. Click to view previous post history.

  8. #28
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    Quote Originally Posted by Katharine Thayer View Post
    As I said in that first post, in watercolor paint the stability of the pigment varies widely across brands, and it's possible that in oil paint it may be the same. Prussian blue in three watercolor brands is rated extremely stable and in a few brands is so fadeprone as to be considered fugitive. My understanding from my reading in the past is that the difference in stability of different brands may have more to do with additives and fillers than with the medium itself; lower quality paints sometimes use a calcium carbonate filler to extend the pigment, which might have a deleterious effect on the pigment.
    Hi Katharine,

    Thanks for all your information regarding paints and your experimentations. I understand your curiosity... having moved between photography and some paintingwork recently.

  9. #29

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    No panic Marco,

    See this (by Mike Ware):

    "...By the way, the ability of the Prussian Blue lattice to act as host for relatively large amounts of impurity ions has recently been put to good use by 'locking up' the radioactivity that was deposited on the uplands of North Wales and Cumbria following the Chernobyl disaster. (11) Spreading Prussian Blue on the contaminated soil inhibited the uptake of Caesium 137 by grass; our lamb chops were thus safeguarded from radioactive contamination, but at the price, perhaps, of turning the green hills of Britain to navy blue!

    ...

    (11). Brewer, K., New Scientist, 138, 10 (1993)."

    URL: http://www.mikeware.co.uk/mikeware/N...e_Process.html

    Also:

    "...Prussian blue's (PB) ability to incorporate +1 cations makes it useful as a sequestering agent for certain heavy metals ions. In particular, pharmaceutical-grade PB is used for patients who have ingested radioactive caesium or thallium (also non-radioactive thallium). According to the IAEA an adult male can eat 10 grams of Prussian Blue per day without serious harm. It is also occasionally used in cosmetic products. The US FDA has determined that the '500 mg Prussian blue capsules, when manufactured under the conditions of an approved New Drug Application (NDA), can be found safe and effective for the treatment of known or suspected internal contamination with radioactive caesium, radioactive thallium, or non-radioactive thallium.' [1]

    ...

    [1]. http://painting.about.com/cs/colourtheory/a/prussianblue.htm"

    URL: http://en.wikipedia.org/wiki/Prussian_blue

    So, I don't think you were intentionally quoting some obscure character; this is scientific information, a fact -> you can't be responsible from other people's take and purpose about this bit of information...

    Regards,
    Loris.

    Quote Originally Posted by Marco B View Post
    Hmmmmm, I'm very,very sorry , I certainly had no intention of quoting any such infamous character...

    Unfortunately, I am not able to edit this post anymore, and remove the quote... Maybe a site or forum administrator could do that...

    Google turned up the result when I searched for some keywords as "stability" "prussian blue" , and although I had a quick look through the article, the 70 pages or so was a bit much and did not immediately raise my suspicion, as it should have~!!!

    Thanks for the useful - and necessary - history lesson... !

  10. #30
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    Quote Originally Posted by Loris Medici View Post
    So, I don't think you were intentionally quoting some obscure character; this is scientific information, a fact -> you can't be responsible from other people's take and purpose about this bit of information...

    Regards,
    Loris.
    Loris: you are confusing my blunder quote / reference, justly corrected by DrPablo, with Katharine's and RWYoung's quotes about the radioactive absorbent properties of Prussian blue... read back and you'll see what DrPablo meant...

    I do appreciate your kindness for defending another person, but my big error was obvious in retrospect...

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