The image is painted on gesso (plaster) on a wooden base. The technique used is called egg tempera, that is, the paint applied being a mixture of dry colour pigment, egg yolk and water. The egg tempera technique is very old and dates from the first centuries AD. It was the standard European painting technique well into the Renaissance. For example, Botticelli’s Birth of Venus is painted in the egg tempera technique. Oil paint gradually replaced egg tempera from the 1500’s. The background is pure gold leaf applied using an oil size.
There are four symbols of the Evangelists around the central figure of Christ; the angel is St Matthew, the lion is St Mark, the eagle is St John and the ox St is Luke. The images come from the biblical books of Ezekiel and Revelations.