Materials and ConstructionThe orange background color of the pot is characteristic of the iron-rich clay found around Athens. An amphora like this one would have been thrown on a potter's wheel. The spiraling ripples one can feel on the inside of the pot are throwing lines and bear witness to the hand of the ancient potter. The body and the neck were thrown separately, allowed to dry to a leather-hard, and then joined together with a loose slurry of clay and water. After the outside surface was scraped smooth, or burnished, the foot, and handles were added. Just before it dried completely, a broad Alpha was scratched into the base of the foot. This graffito might have been used for inventory control; similar marks are found on pots made in Greece for export.
DecorationAncient Greek vase painters used specially prepared clays mixed with different coloring agents. This prepared clay is neither glaze nor paint, but more properly called slip or gloss. The key color, a shiny black, consisted of a finely purified form of the regular clay, which turned black in the kiln when fired to a certain temperature under oxygen-deprived conditions. Two other colors often found on Greek ceramics, a purplish red and a yellowish white, can also be seen on the Hampden-Sydney vessel. The purplish red is produced by mixing red iron-oxide pigment (ochre) with water and the black slip. The white is made by using a very pure clay with almost no iron oxide in it.
FiringLike all ceramics, the Hampden-Sydney amphora was fired in a kiln. The ancient Greeks fired their ceramics once after they were painted. This single firing had three distinct phases that allowed the clay body of the vessel to turn rich red-orange while the slip-painted areas turned glossy black. First, the pots were fired to a temperature of about 800 degrees Celsius (1472 degrees Fahrenheit) under oxidizing conditions (with free access to air). During this stage the vases turned red all over. In the second phase, the oxygen level was reduced by introducing green wood into the firing chamber and closing the air vents. Under these circumstances, the temperature was raised to 900 degrees Celsius (1652 degrees Fahrenheit) and the vessels turned all black. In the third and final stage, the atmosphere was returned to an oxidizing one and the kiln was allowed to cool completely. As the temperature lowered from 900 degrees in an atmosphere once again rich in oxygen, the vessels turned red once more, but the areas painted with slip remained glossy black. The division of color and texture is caused by the partial vitrification, or sintering, of the surface of the slipped areas at the moment of highest temperature in the second stage, a sealing of the surface that prevents the re-entry of oxygen into the clay and subsequent return to red color in the final stage. If the temperature were raised too high in the third phase, oxygen would re-enter the slipped areas and they would go red again. So this method of vase decoration depended on careful control of both the temperature and the atmosphere of the kiln.