Examination of the Gayer-Anderson cat
The Gayer-Anderson cat is one of the best known objects in the British Museum collection, but until recently it had not been studied by the Museum’s scientists. In 2007 the cat was X-rayed, analysed and carefully examined under a microscope. This produced a range of results, some expected and some far more surprising.
By studying the surface and taking X-rays, which were then magnified, Museum scientists discovered small square features all over the body. These are metal ‘core-pins’ or ‘chaplets’ and show the cat was produced using a process called lost-wax casting.
Using X-ray fluorescence (XRF), scientists have been able to find out what the cat is made from. XRF works by directing a beam of X-rays at an area of the object, which give an analysis of the elements present in the surface layers. However, because the surface layers of the cat have been heavily altered and painted it was difficult to find a clean area of metal on the surface to analyse. Instead a tiny metal sample was drilled from the bottom of the sculpture. Analysis of this sample showed that the body metal of the cat (uncontaminated by the green surface) is made of bronze containing 85% copper, 13% tin, 2% arsenic and 0.2% lead.
The examination also showed how much the cat was repaired before it came to the Museum in the 1940s. It was always known that there were some cracks in it, but the X-ray showed that damage was more extensive than previously thought. There is a large crack all the way around the body (because an X-ray shows both sides of an object at once, this looks like a double line).
X-rays of the head of the cat revealed a metal cylinder, held in place with a series of hooks and wires, fitted inside, probably to stop the head from falling off.
The surface of the object has also been changed. When it was dug up in the early twentieth century it would have been covered in a thick layer of green and red corrosion formed during its burial.
We know Major Gayer-Anderson, who owned the cat in the 1930s, was a keen restorer of ancient metal objects and that he cleaned off much of this material. He probably applied a thick layer of green paint (containing the pigment Brunswick Green, which was in frequent use in the 1930s), which also helped disguise some of the repairs.
These changes make it very difficult to know exactly what the cat would have looked like when it was made. We know from other ancient Egyptian bronzes that they were often originally brightly coloured, with inlays of semi-precious stones and areas of different coloured metals.
A silver necklace and plaque still remain around the cat’s neck and the ears and nose are pierced to hold jewellery (although the current earrings, while ancient, might not be original to the cat - in an early photograph the cat is shown wearing a different pair).
The eye sockets, which are now empty, would originally have held eyes made of stone or glass.
Analysis of small strips of metal wrapped around the tail showed that they are made of a different metal alloy to the rest of the cat and would have been a different colour, producing the effect of a striped tail.
The exact colours would have depended on how the metal was treated. It could have been polished to show the subtle natural difference in metal tone, or coloured. This colouring is known as patination and is the deliberate treatment of the metal to give an attractive coloured layer on the surface. We know from other temple figures that this was a technique used by ancient Egyptian metalworkers.