Coffin Conservation: Part 1 (written by Bethany Palumbo)
When Tahemaa died 2700 years ago, she was wrapped in linen and buried in an elaborate coffin. The coffin, made from wood, was layered with plaster and fabric to create the gentle curves and shape of the coffin. On top of this is the painted layer, created with mineral pigments mixed in a natural gum or resin to make a paste. While we still need to officially identify the pigments and materials used in the composition of the coffin, we can see how they are deteriorating.
These types of organic materials are extremely vulnerable to deterioration caused by environmental changes. As the environment around Tahemaa becomes hotter or colder, more humid or drier, the materials used to make the coffin expand and contract. These fluctuations, repeated over many centuries, have caused the wood, plaster and paint to crack and flake. The layers of the coffin have even separated in some areas, lifting away from the wood (figure 1).
Figure 1- Layers of the coffin structure peeling away.
Many decades without a display case has also resulted in a large build-up of fine, engrained dirt and this is concealing the bright colours of her decorative paintwork (figure 2).
Figure 2- Original colours are darkened with the build-up of surface dirt.
While we want Tahemaa restored to her formal glory, her age and historical significance means that any conservation treatment undertaken needs to be sympathetic and minimal. The priorities of treatment for the coffin are therefore to clean the surface to remove the accumulation of dirt and to consolidate the paint and plaster layers to prevent any further cracking or surface losses.
The first step of cleaning is to use dry methods. This was undertaken using ‘smoke sponge’ a type of vulcanized rubber that could be gently wiped over the surface. This picked up lots of loose surface dirt. Afterwards I decided to further clean Tahemaa with solvents, but decided against aggressive chemicals or detergents. Instead I decided to clean Tahemaa’s coffin using human saliva. While somewhat controversial, human spit is used in museums all over the world as a tested and highly effective cleaning method. Human spit contains 99% water and 1% enzymes and it is these enzymes that breakdown the dirt. Spit also evaporates, leaving behind no chemical residues that would require rinsing.
Using cotton swabs, I gently cleaned the surface of the coffin (figure 3) adjusting my technique for areas of existing surface damage.
Figure 3- Cleaning the coffin with cotton swabs and a lot of patience.
The result is amazing, with dark areas lightened, the gorgeous colours of the paint work underneath can now be seen (figure 4).
Figure 4 – Shows the effectiveness of enzyme cleaning on the painted surface, before (left) and after (right).
This process is time-consuming but for an object like this coffin, patience is key! You can find me in the Egyptology room at the BNSS every Tuesday for the next few months carrying out this work so please come by and say ‘hi’.
Bethany Palumbo 27th July 2019
http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/006/300/B002_Egyptian_Pigments_and_Materials%203.pdf. Royal Society of Chemistry, online article.
https://www.iiconservation.org/node/732 International Institute for Conservation, Studies in conservation, Volume 35, Number 3, p.153-155 (1990)