[Bonetools] Colouring bone

Thu Apr 17 14:56:13 CEST 2014

Dear Sonia and Vincent, 

Thank you for your replies. 

I have successfully produced a reasonable quantity of verdigris myself for staining experiments, using the method you described Vincent, but I haven’t tried it with urine yet. Did you try dyeing any material when you produced it, or was the production of verdigris alone the experiment?

So the rivets in this comb (http://balat.kikirpa.be/photo.php?path=X035781&objnr=20052916) were bronze? I had thought iron from the brown around them, and presumed it was ferrous staining.

Regards,

David Constantine

From: Vincent Cattersel 
Sent: Thursday, April 17, 2014 1:36 PM
To: Mailing list for archaeologists of the research group for the study of object and waste of bone, antler. ivory and horn. 
Subject: Re: [Bonetools] Colouring bone

Dear David and Sonia, 

the rivets were bronze so the green colouration could well be coming from the rivets' oxidation. However this staining was limited to the surface (surface of the cortical bone) and not in sub-surface layers. Therefore we assume that the colouration was done deliberately.  
Based on our data, a relationship with a certain recipe wasn't possible but we think it was a copper based product (so called verdigris, basic copper acetate, Cu(OH)2 · (CH3COO)2 · 5 H2O). 

You also mention the use of urine, which was frequently used for producing metal salt based pigments. The urine itself induces the corrosion on the copper sample. After it is corroded, one can scratch of the crystals, grind them to the desired particle size, add a medium (e.g. oil, wax) et voilà, a green pigment. See these two pictures from an experiment I have done in 2003. 

On the first picture you can see small slabs of copper hanging above vinegar (I could have well replaced the vinegar with urine). There should be no contact between the copper slabs and the fluid. The vapours of the fluid induces the corrosion process. On the second picture you can see the actual scrapings of the copper acetate crystals, which are ready to use. One often read in historical recipes that the jar should be buried in horse dong. The bacterial activity in the latter produces heat (sometimes +70° Celcius) and therefore it significantly increases the corrosion process and reduces the production time. 

Sonia: 
the object you have mailed also has the same green colouration as I would expect from an object coloured with a basic copper acetate based pigment. What draws my attention is the brownish decolouration on both sides of that object. Copper acetate is quite unstable and when exposed to light and a 'high degree of humidity' it turns into the more stable molecule copper oxide, which is brown to black.

Yours,
Vincent Cattersel

On 17 April 2014 13:36, SA O'Connor <S.Oconnor at bradford.ac.uk> wrote:

  Dear David,

  Back in the 1980s, when I was at the York Archaeological Trust we were involved in providing green stained objects for an undergraduate dissertation by a University of Bradford, Archaeological Sciences, student (surname of Edwards, I think) to look at exactly this question.  Some objects seemed to be accidentally stained (often very patchy) whilst others were intensely and evenly stained and were considered to be deliberately coloured. All were analysed by XRF and copper/bronze proved to be the basis of all the staining solutions used.

  In my more recent work I have documented historical pieces, such selected elements of bone and antler in box and gun inlays and bone and ivory cutlery handles(and working waste from cutlers) that are undeniably deliberately stained.

  I attach a low resolution image an archaeological example, a buckle at the Yorkshire Museum that I am convinced is deliberately stained in this way.

  All the best,

  Sonia

    Quoting David Constantine <dkconstantine at btinternet.com>:

    I am aware that copper (or alloys) is often cited as a green dye for (such as in MacGregor 1985), but I believe there is also recipes from the Mappae Clavicula that use weld, urine and "lulax" to dye bone green, so I was curious to see if any chemical analysis has been performed to determine how the green has been achieved.

    Looking at the zoomed images, I believe the rivets are iron.

    Regards, 

    David Constantine 

    ________________________________
    From: Kordula Gostencnik <kgosten at gmail.com>
    To: "Mailing list for archaeologists of the research group for the study of object and waste of bone, antler. ivory and horn." <bonetools at listserv.niif.hu>
    Sent: Wednesday, 16 April 2014, 20:21
    Subject: Re: [Bonetools] Colouring bone

    Green stains are normally caused by bronze objects or copper alloy scrap associated with worked bones in the soil. Are the rivets all made from iron or also from bronze?

    Kordula

    2014-04-16 17:15 GMT+02:00 Dave Constantine <dkconstantine at btinternet.com>:

    Thank you all for your replies.

      Vincent, the green stained comb you linked is rather interesting. Do you

    know what the green pigment is? Also, looking at the images, it seems that it is
    no more than a surface colourant with little penetration, is this correct?

      Thank you for your suggestion of minium, I was at a loss about what it

    could be. It is not a fresh find, it was originally discovered in the 1960s (or
    possibly 1970s) and mounted on a card for display. To the best of my knowledge
    though, the colouring is original, though it is possible that the surface was
    also coloured and this has simply failed to survive.

      I have Arthur MacGregor’s book, and very useful it is too on the matter of

    colouring.

      Regards,

      David Constantine

      From: Vincent Cattersel
      Sent: Wednesday, April 16, 2014 2:03 PM
      To: Mailing list for archaeologists of the

    research group for the study of object and waste of bone, antler. ivory and
    horn.

      Subject: Re: [Bonetools] Colouring bone
        Dear all,

      this is a first where I might be able to contribute to this group, but I'm

    happy to do so:

      In 2008 I have conserved and restored 8 bone/antler combs from the

    Merovingian period at the Royal Institute for Cultural Heritage (Brussels,
    Belgium). These combs are currently preserved at the Royal Museums of Art and
    History in Brussels, Belgium.

      Here you can find pictures of a few of them (click on the pictures to get a

    zoomable high resolution image):

      http://balat.kikirpa.be/photo.php?path=X026849&objnr=20042741

      http://balat.kikirpa.be/photo.php?path=X035781&objnr=20052916

    (green staining on the surface, carbon black in the circular
    motives)

      http://balat.kikirpa.be/photo.php?path=X026845&objnr=20052917

      http://balat.kikirpa.be/photo.php?path=X038388&objnr=20052919

      http://balat.kikirpa.be/photo.php?path=X035783&objnr=20052922

      Some of these where coloured and stained with green and carbon black. We

    used µ-XRF, µ-RAMAN and SEM(-EDX) to analyse the stains and the carbon black
    particles.

      So staining and colouring isn't that uncommon, as you probably already

    know.

      When I look at the picture, I can see that the red is slightly orange,

    which makes me think about the pigment lead red (also called 'minium' or lead
    tetra-oxide, Pb3O4). This isn't a
    surprise since it is one of the oldest known vivid red pigments (except for some
    iron oxide pigments derived from hematite and red earth or cinnabar (HgS),
    however they all are true 'reddish' in colour and lack the hint of orange).

      Some simple identification techniques for minium are:

              * Ultraviolet fluorescence (if minium, it minium it should show a dark red  colouration);

              * Infrared False Color which should gives the observed minium a yellow-brown  colour. Analytical techniques: 

      In case you have the oppurtunity to

    analyse it with RAMAN, you can find a reference spectrum here.

      For

    a reference spectrum of minium using XRF: here.

      Another thing is the question whether this die was excavated and brought

    directly to your collection or was it once part of a (private)collection and
    excavated a long time ago.

      This is an important question since it could provide an answer to whether

    or not this colouration is original.

      I know from my experiences with the conservation of precious ivory objects

    that they are often repainted (repolychromed) throughout time, even though their
    iconography or typology gives us reasons to believe that they originally weren't
    polychromed or not polychromed in such manner as they are today.

      To get back on the minium pigment, more information can be found in:

              * Eastaugh, N., Walsh, V., Chaplin, T., & Siddall, R. (2008). Pigment  Compendium - A Dictionary and Optical Microscopy of Historical Pigments.  Oxford: Butterworth-Heinemann.

              * Feller, R. L., Gettens, R. J., & Chase, W. T. (1993). Vermilion and  Cinnabar. In R. Ashok, Artists' Pigments - A Handbook of Their History and  Characteristics. (Vol. II, pp. 159-182). Washington-London: National Gallery  of Art. 

      Another book I can recommend on staining and colouring bone materials is:

    McGregor. A. (1985) Bone, Antler, Ivory & Horn: The Technology of Skeletal
    Materials Since the Roman Period.

      I don't have it here with me for the moment, but as you wish, I can always

    go through it to find more information on red staining or colouring.

      Yours,

      Vincent Cattersel

      Drs.

    VINCENT CATTERSEL

      Doctoral researcher
      Universiteit

    Antwerpen / University of Antwerp

      Faculteit

    Ontwerpwetenschappen / Faculty of Design Sciences

      Opleiding

    conservatie-restauratie / Conservation Studies

      Blindestraat

    9

      B-2000

    Antwerpen

      T +32 3 213 71

    34 | F +32 3 213 71 35

      vincent.cattersel at uantwerpen.be
      www.uantwerpen.be

      On 15 April 2014 09:06, David Constantine <dkconstantine at btinternet.com> wrote:

        Hello All,

        Attached is an image of a (probably) Saxon bone/antler  die. As can be seen, there is reddish pigmentation in the decoration. I have  looked around for similar colouring and with the exception of a "lucet" from  London I cannot seem to find anything similar, just totally stained objects  e.g. the belt buckle from York. Does anyone here know of any Early Medieval  dated bone artefacts that are either entirely stained/dyed or have coloured  decoration such as this?

        Regards,

        David

      Constantine

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