[Bonetools] Colouring bone

[Vincent Cattersel]

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
<goog_468693376>
http://balat.kikirpa.be/photo.php?path=X035781&objnr=20052916 (green
staining on the surface, carbon black in the circular motives)
<goog_468693376>
http://balat.kikirpa.be/photo.php?path=X026845&objnr=20052917
 <goog_468693376>
http://balat.kikirpa.be/photo.php?path=X038388&objnr=20052919
<goog_468693376>
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<http://www.chem.ucl.ac.uk/resources/raman/pigfiles/redlead.html>
.
For a reference spectrum of minium using XRF:
here<http://cameo.mfa.org/images/8/82/Slide16_FC199.PNG>
.


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<https://mail.uantwerpen.be/owa/redir.aspx?C=Gp6oB9zg6EOuD7R75-KaedCX7IvSydAI3RAu53oKfBVI3Qv2NuFbAdGDGuoXVIRgfT68F3LfWbc.&URL=http%3a%2f%2fwww.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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