I have been quite intrigued by the red coloured medieval tablemen that are found in the different museum collections around the world (for instance the Metropolitan Museum of Art, the Victoria and Albert Museum, the Museum für Angewandte Kunst Köln, among others). How were these pieces coloured and is this easy to reproduce? The how was easily answered, as the monk Theophilus provides a recipe in his book 'On divers arts' which was written around 1122 - a similar date as most of the red game pieces, which were manufactured in workshops in Cologne, Germany.
A game piece with Samson slaying the Philistines with the jawbone of an ass. Madder coloured walrus ivory. 6.3 by 1.3 cm. Made in Germany around 1140-1150. Photo Metropolitan Museum of Art, Cloisters, New York, NY, USA.
Theophilus writes in Chapter 94 of his book:
'There is also a plant called madder, whose root is long, thin, and reddish. After it is dug up, it is dried in the sun and pounded in a mortar with a ball. Then lye is poured over it and it is cooked in a raw pot. When it has boiled well, if the bone of an elephant or a fish or a stag is put in it, it will become red. from these bones or horns knops can also be made on the lathe for the staves of bishops and smaller knops for various useful objects. When you have turned these with sharp tools, smooth them with shavegrass. Collect the shavings on a linen cloth and, still turning the lathe, rub them vigourously on the knops which will then become completely shining. You can also polish horn-handles, huntsmen's horns, and [horn] windows in lanterns with sifted ashes on a woolen cloth. But do not forget to smear them finally with walnut oil.'
Of course the bone of an elephant is ivory, the bone of a fish relate to normal animal bone, and the bone of a stag is antler. I am unsure if Theophilus also means that (cow, goat) horns can be stained, as these have a quite different structure more similar to nails and hairs. However, wool for medieval clothing is commonly stained with madder. There is evidence that madder was already cultivated for this purpose in the Netherlands in the 12th century; in later centuries the Dutch madder became famous for its quality.
A similar uncoloured game piece with Hercules throwing Diomedes to his man-eating horses. Elephant ivory. Made in Cologne, Germany around 1150. Diameter 7 by 2 cm. Photo Metropolitan Museum of Art, Cloisters, New York, NY, USA.
As I was making a set of alquerque game pieces from antler, I wanted to make one set coloured red. The recipe of Theophilus was not very specific. In fact it looked more like a medieval cooking recipe without amounts. Searching on internet did show many recipes for colouring with madder, but these all concerned wool or cotton, and all are different as regards to amounts of the ingredients.
A mordant - alum - is needed to fix the red colour to wool. The wool is first treated with the mordant, and then to the colouring solution. For cotton and hemp, both non-animal (plant) fabrics, an extra pretreatment is necessary before the alum. On the other hand Theophilus, as well as the early 18th century scientists do not mention alum at all for bone colouring.
There are also other steps in the colouring process that need to be considered: temperature influences the colour; a temperature above 82 degrees Celcius turns the red colour into brown (for wool). Hard water (basic pH) increases the intensity of the red colour. The time in the colour solution and the strength of the colour solution influence the outcome as well: the longer, the darker, and more pigments in the solution also make the end result a darker red.
So what is the best way to colour antler madder red? I decided to do some tests to find out.
The first test
Madder powder as well as madder extract was bought from paint mill '
De Kat' in the Netherlands. Madder extract has already the red pigments (alizarin and purpurin) from the root extracted, and is sold as a plaque of dried crystals, which needs to be dissolved again. The madder powder is finely ground madder root, from which the madder pigments still need to be extracted before colouring the antler (or wool). I also purchased some alum from 'De Kat'.
Left: The two basic madder preparations from powder and extract in the 60 degrees Celcius water bath. Right: the setup in the kitchen with the meat thermometer at 60 degrees.
The amount of dyestuff needed is based on a percentage of the weight of fibre (WOF), in my case the weight of the antler pieces. For madder powder this is 35-100% WOF, for madder extract this is 3-8% WOF. The antler pieces should be just fully immersed in the solution. So the actual amount of water does not matter, the amount of pigment that is available to the fibre does. I used 50% WOF for the powder and 4% WOF of extract.
Left: Pretreated antler pieces: with water in the glass, or with alum in the plastic box. Right: Four smaller test pots in the 60 degrees Celcius water bath.
Half of the antler test pieces were pretreated with alum, 15% WOF (as for wool). The other half was only immersed in water. During mordanting, the solution with the antler pieces was kept around 60 degrees Celcius for one hour. The pots with the solution were heated au-bain-marie (a waterbath) in a pan on a low flame and the temperature was kept in check using a digital meat-thermometer. If the temperature started to rise, a bit of cold water was added to the pan. After one hour, the pots were left to cool.
I made 400 ml of each madder solution. The pots with the madder solution were placed at 60 degrees Celcius for
one hour in the waterbath, as described above. During the hour the
colour of the powdered solution darkened, the extract solution was
quickly dissolved and had a similar dark red colour.
Then the pretreated antler pieces were divided over smaller pots and the colouring solutions added. To the pots with antler pieces without alum an extra 2 gram of household sodium was added to each madder solution. The sodium carbonate was used to raise the pH of the solution to see if this influences the intensity of the colour. The test consisted of five pots:
- Antler mordanted with alum, madder powder solution, with sodium added during cool-down
- Antler mordanted with alum, madder powder solution, no sodium
- Antler mordanted with alum, madder extract solution, with sodium
- Antler with water, madder powder solution, no sodium
- Antler with water, madder extract solution, with sodium
The pots were kept around 60 degrees Celcius in a waterbath for 2 hours, after which they were left to cool down for 24 hours. Then the antler pieces were rinsed with cold water and dried.
Colour after 2 h 60 C degrees bath. The darker red coloured pieces on the right are without alum pretreatment and with sodium.
The colour after 24 h cool down with the same oder of test pieces. The piece on the far left (powder + S + alum) was treated with sodium during the cool-down period and gained in colour strength.
As it turned out, mordanting with alum did have no positive effect on the colouring process for antler. Sodium, on the other hand, did. All antler pieces in a solution containing sodium were dark red, the one with sodium added later medium red, while those without were only lightly red coloured. Both the madder extract and the madder powder did colour equally well. Madder powder is cheaper than madder extract, but madder extract is a clearer solution and does not have the risk of the powder grains to become affixed to the antler. So the extract was used for further experimentation (in the next blogpost).
A side note
Science also had an early interest in colouring bones red. The first scientific study on the effects of madder on bones is from the early 18 century by M. Du Hamel du Monceau and published in the Philosophical Transactions of the Royal Society of London. An observation from a surgeon eating a pig with red bones, led to experiments where pure ground madder was (forcibly) fed to chickens, which died after a few days. Indeed, the chicken bones had become all red, but not the feathers.
Nowadays the synthetic red pigment (alizarin) that is also found in madder is still used to study the growth of bones and their calcium deposits.
Smooth newt (Triturus vulgaris) with bone coloured with alizarin. Bar = 5 mm.
Sources
- G.C.H. Derksen (2001) Red, redder, madder. Analysis and isolation of anthraquinones from madder roots (Rubia tinctorum). PhD thesis, Wageningen University, Wageningen the Netherlands. https://edepot.wur.nl/197629.
- M. Du Hamel du Monceau (1739) Observations and experiments with madder-root, which has the faculty of tinging the bones of living animals of a red colour, by M. Du Hamel du Monceau, F.R.S. & c. Communicated in a letter to Sir Hans Sloane, Bart. Pr. R.S. Translated from the French by T.S. M.D.F.R.S. The Royal Society of London Philosophical Transactions Vol. 41, pp. 390-406. https://www.jstor.org/stable/104301
- Antje Kluge-Pinsker (1991) Schach und Trictrac. Zeugnisse mittelalterlicher Spielfreunde in salischer Zeit. Jan Thorbecke, Germany.
- Vivian B. Mann (1977) Romanesque ivory tablemen. PhD thesis, New York University, New York, USA.
- Theophilus (1122) On diverse arts. Translated by J.G. Hawthorne and C.S. Smith (1979) Dover Publishing, Garden City, NY, USA.
- The Maiwa guide to natural dyes - what they are and how to use them. https://naturaldyes.ca/instructions
