Written by Lydia Amies, Conservation Assistant, Natural History Museum London
In 2018 I was lucky enough to start as a Conservation Assistant funded by the Calleva Foundation at the Natural History Museum, London. The Calleva Projects at the NHM focus on researching ancient human populations of the UK as well as human evolution and behaviour more generally. I work primarily on Anthropological specimens including Fossil Mammal specimens, repairing, cleaning, making casts, as well as creating mounts for storage and re-boxing specimens. Fossil mammal remains help us form a picture of the environments inhabited by early humans in Britain, and there are many important collections with interesting objects and stories in association with humans where either tools or direct human evidence on fossil mammal specimens are obvious. As you will see, the specimens I work with are very varied and I hope you will enjoy having a look at what I’ve been up to.
Creating replicas of Gough’s Cave ivory specimens. PAL 2020-498 PV on loan from Longleat Estate. ©Trustees of the Natural History Museum.
Gough’s Cave Ivory
These artifacts were found in the late 1980s in Gough’s Cave, Cheddar Gorge. They are made of mammoth ivory and are thought to be around 154 thousand years old. We don’t know exactly how they were used, but researchers think they may have been some kind of hunting tool. The specimens are made up of a few large ivory rods and smaller, more broken fragments. Some of the larger pieces feature beautiful intricate carved detail.
Gough’s Cave ivory pieces showing carvings. PAL 2020-498 PV on loan from Longleat Estate. ©Trustees of the Natural History Museum.
The porous nature of ivory means it is very sensitive to changes in relative humidity which can cause problems like warping and cracking. We 3D surface scanned the specimens so that we have an accurate record of how they are now, in case there is any deterioration. We also used the scan images to 3D print replicas, which were also used to create mounts.
Top: One of the original Gough’s Cave ivory specimens. PAL 2020-498 PV on loan from Longleat Estate. Bottom: 3D printed, hand painted replica. ©Trustees of the Natural History Museum.
The most complete specimens will be mounted on Perspex with small cushions of cotton fabric held in place with Paraloid B72 adhesive to prevent abrasion. Once mounted the specimens will not only look impressive but the mount will allow more of the object to be seen, reducing handling and the associated risk of damage.
Correct storage environment is essential for these fragile specimens. UV light can have a bleaching effect on ivory. Its porous nature also puts it at risk of discolouration from oils in skin, dyes and staining from corroding metals. Once re-boxed, the specimens will be kept in an area with strict environmental controls, maintaining a temperature of 20-22oC and a relative humidity of 45-55%.
Re-storage is an important part of preventative conservation. Almost all of my projects involve an element of re-evaluating storage solutions. A well-made box with a mount prevents damage to the object through reducing movement and abrasion, as well as encouraging more careful handling. Conservation grade boxes are usually hand-made, with Plastazote® foam cut out mounts to support the specimens.
New, custom-made storage for some of our fossil mammal specimens. Left: NHMUK PV M 102320 from Barnham, Suffolk. Right: NHMUK PV M 48525 Cervus elephus metacarpal from Westbury Quarry Cave, Westbury-sub-Mendip. ©Trustees of the Natural History Museum.
Clacton Rhino Skull
The largest specimen I have worked on so far is the skull of this extinct species of a narrow-nosed rhinoceros that lived in the UK and other places in Europe during the Middle Pleistocene. This specimen was discovered in Clacton, Essex. It has some structural cracks which were repaired some time ago with plaster, but this had obscured quite a large section of the surface of the bone. This was a problem as researchers were looking for cut marks as evidence of butchery on the specimen. The curators asked us to check the condition of the skull and, if possible, remove the plaster and stabilise, using a less intrusive method.
Before and after removal of one of the plaster fills on Clacton rhino Skull NHMUK PV OR 27836. ©Trustees of the Natural History Museum.
We experimented with the best way to remove the plaster, first using the least interventive method by attempting to soften the plaster with solvents such as water and acetone, before lifting it with a wooden cocktail stick. Unfortunately, the plaster was coated in an unknown varnish which was resistant to solvent removal, so I moved onto mechanical means using an airgrinder abrasive to gently wear it away. An Epopast 400 (epoxy paste) clam shell jacket was made and lined with Plastazote® to support the skull and enable it to be handled, turned and stored safely.
The Clacton rhino skull supported by an Epopast 400 Jacket in its new home. NHMUK PV OR 27836. ©Trustees of the Natural History Museum.
Unfortunately, the Covid pandemic has led to the temporary closure of the NHM which has delayed some of my practical projects. However, I am excited to get back to looking after my specimens in person soon. I have a Neanderthal skeleton and more fossil mammals that I am itching to get my hands on!