Our ‘Medieval’ Wax and the Magical Aging Chamber

As you might remember, a few months ago we spent the day in a lab using medieval recipes to make sealing wax. We had been careful to ensure that we had followed the recipes as closely as possible in order to replicate the methods used in the Middle Ages (ignoring the fact that medieval seal makers tended not to frequent state-of-the-art conservation labs…), but we were curious to know the extent to which our sealing wax was authentically ‘medieval’. Our friends in Conservation said they could help us with that, and so we took our wax over to a different lab, where we used a Fourier Transform Infrared (FTIR) Spectrometer to have a look at the chemical composition of our wax.

“What is a Fourier Transform Infrared Spectrometer?”, I hear you ask. Well, it is a clever machine that uses a mathematical model called a Fourier Transform to measure the absorption or emission of infrared by the material (in our case, sealing wax). The bonds between elements absorb infrared of different frequencies, which then causes them to vibrate. The FTIR spectrometer shines monochromatic infrared light onto the wax, records how much of the light is absorbed, and then repeats at different wavelengths until a complete picture can be formed.

FTIR readout for our red and green wax. The green line is red wax and the pink line is green wax (I tried, but I couldn't get it the other way around).
FTIR readout for our red and green wax. The green line is red wax and the pink line is green wax (I tried, but I couldn’t get it the other way around).

We can see from the readout that our red and green bits of wax had a similar composition, which is reassuring as beeswax and resin were used in both, but that verdigris and vermillion did make some difference to the ways in which the bonds were formed.

Our friends in Conservation then placed a piece of our red wax inside a magical Artificial Aging Chamber. An Artificial Aging Chamber uses heat and humidity to replicate the aging process, as warm, wet conditions speed up reactions. It is estimated that every 5-10°C doubles the rate of aging. Our wax was put in at 40% humidity and 40°C (any higher and it would have started to go soft) for about a month, and so was ‘aged’ by about 40 years. We then did some more FTIR spectroscopy. We compared the aged piece of wax to the unaged wax and also against a piece of wax from a seal of Richard II.

FTIR readout. Red=  unaged wax; Black= aged wax Blue= Richard II seal
FTIR readout. Red= unaged wax; Black= aged wax Blue= Richard II seal

As you can see, the black (aged wax) and blue (Richard II seal) lines are much closer together than the blue and red (unaged wax) lines. There is some variation, as we do not know the recipe used to make Richard II’s seal. This is an ongoing project, and we intend to continue aging our wax and analysing its composition, but we can see that as our freshly-made ‘medieval’ wax ages, it becomes more like ‘medieval’ wax as we know it.

Hollie L. S. Morgan

The curious case of the pressed-in ring

After two weeks of training with our specialist equipment, we were unleashed into The National Library of Wales to work on the Penrice and Margam charters.

January is a strange time to be introduced to Aberystwyth: it is beautiful, the people are very friendly and there are postcards in the shops saying ‘Come to Sunny Aberystwyth’ but it is also freezing cold, very windy and the sea is out to get you. I spent four weeks in various lonely B&Bs including one week on the sea front during a storm. I lay in my bed watching the waves crashing against my third-floor window until the proprietor came to tell me to close the curtains ‘just in case they get smashed’. The next morning involved a daring escape through the basement kitchen and up a fire escape, a dash past closed-off roads, dodging waves and flying rocks and a battle against the wind up the hill to arrive, soaking wet, at what seemed at that moment the best place on earth. The National Library of Wales is a wonderful place where you’re greeted in both Welsh and English, where the gift shop sells everything from books and cards to jewellery and whisky and where the cafe serves tea in pots and soup with cheese. Their collections include the Hengwrt Chaucer, Piers Plowman and, of course, charters with lots of beautiful seals, covered in prints.

While we saw many beautiful and interesting seals depicting knights on horseback, flowers, enthroned bishops and heraldry, my favourite was a seal without a matrix impression at all. Penrice Margam charter 123 has a seal with the impression of a ring in it. Not the impression of a signet ring, but the whole ring, pressed into the wax.

Seal of Aberystwyth, The National Library of Wales, Penrice and Margam charter 123

The charter itself is a quitclaim by Wenthlian, daughter of Morgan, to Margam Abbey, of a meadow and gorse land which belonged to her father. The charter is small in comparison to the seal and the attachment, which is a long, plaited cord of at least two colours. It seems to me a little incongruous: someone seems to have made a big deal of sealing the charter and attaching the seal, and yet the seal matrix is lacking. Was it simply overlooked, or was it a deliberate choice to press a ring (perhaps with monetary or sentimental value)? Using the Crime-lite Imager, we found prints in the centre of the ring impression.

The seal under the Crime-lite Imager

I would love to think that these are the ring and  handprint of Wenthlian, daughter of Morgan. Unfortunately, we will never know for sure. What it does tell us, however, is that seals and sealing practices were not as straightforward as people might think. If a seal was simply a mark of an individual, what does this impression say? While a ring could be a signifier of authority, it means little in profile. One could deduce that it was the act of sealing that was important for this person, rather than the seal itself. In that case, perhaps it was Wenthlian after all who, lacking in a seal matrix and unsure of the technique, was nonetheless determined to make an impression.


Hollie L. S. Morgan