[Bonetools] Colouring bone

Thu Apr 17 14:36:59 CEST 2014

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.
[image: Inline images 2]   [image: Inline images 1]
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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