Terra sigillata

Terra sigillata is a special kind of pottery that has been used and studied for many years. It has three main meanings: as a type of earth used in old medicine, as a name for fine red ancient Roman pottery with a shiny surface, and as a modern pottery technique inspired by the ancient style. Even though it is often translated as "sealed earth," the name really means "clay bearing little images" because it comes from a word for small decorations made by the makers.

In archaeology, terra sigillata usually describes a kind of tableware made in Italy and in places like France and Germany during the time of the Roman Empire. These pots had a smooth, shiny surface that ranged in color from light orange to bright red. They were made in large factories and sent all over the empire. The pots from Italy are called Aretine ware, named after the city of Arezzo, and those from France and Germany are often called samian ware. These pots help scientists learn about the Roman economy because they can tell when they were made and where they traveled.

Today, some potters use the term "terra sigillata" for a technique where they make a very thin liquid slip from clay and polish it to create a shiny finish. This is different from the ancient pots, which did not need polishing. The modern shine only stays if the pot is fired at a low temperature.

Roman red gloss pottery

In archaeology, the term terra sigillata usually refers to a type of fine red pottery made in ancient Italy and Gaul. This pottery was known for its smooth, shiny surface and was very popular in the Western Roman Empire from about 50 BC to the early 3rd century AD.

Italian and Gaulish pottery makers created matching dishes, bowls, and serving vessels in standard shapes. These shapes changed over time and were carefully classified by scholars. Many of the decorated pieces were made in moulds with designs pressed into them, sometimes using small stamps. The decorations often included figures from myths, animals, and plants, reflecting the artistic styles of the time.

The pottery from Gaul, especially from places like La Graufesenque, was made on a large scale. One big kiln there could fire up to 40,000 pieces at once. The red colour of the pottery comes from the size of tiny crystals in the glaze, not from the firing process as once believed.

Gallery of Roman terra sigillata

Here are some examples of Roman terra sigillata pottery:

• South Gaulish cup, form Hofheim 8, with a marbled slip
• South Gaulish cup of form Dragendorff 27
• Flanged bowl, Dr.38, with profile drawing
• Gaulish Dr.36, with barbotine decoration on the rim
• Profile drawing of form Dragendorff 11. 1st century BC–early 1st century AD
• Profile drawing of form Dragendorff 37. 1st–3rd century AD
• Profile drawing of form Dragendorff 30. 1st-2nd century AD

Modern pottery

In modern times, the term terra sigillata has a different meaning. In contemporary ceramic art, it describes a special kind of liquid clay slip used to make the surface of pottery very smooth and shiny. This is done in low-temperature firing methods, such as primitive and unglazed Raku styles. Terra sigillata can also be used as a colorful brush-on coating in higher-temperature glazed ceramic techniques.

Ancient terra sigillata pots have become popular collectibles, leading to many copies being made.

In 1906, a German potter named Karl Fischer created a new way to make terra sigillata like the ancient Romans did and received a patent for his method in Berlin at the Kaiserliche Patentamt.

Making modern terra sigillata

Today, terra sigillata is made by letting clay particles settle into layers based on their size. A special liquid, such as sodium silicate or sodium hexametaphosphate, is often added to help the clay separate. After about a day, the layers become clear: water on top, the terra sigillata in the middle, and thicker clay at the bottom. The middle layer, which has the smallest clay particles, is collected to make terra sigillata. The larger clay at the bottom is thrown away.

The terra sigillata is then applied in thin layers to almost dry, unfired pottery. It is smoothed with a soft cloth or a hard, smooth object before the water soaking into the piece. The pottery is then fired at a lower temperature than usual, which helps keep the smooth surface.

Reuse of Roman pottery

Since the 1700s, people near Whitstable and Herne Bay have found enough ancient Samian ware pots in the sea to use them for cooking.

Medicinal earth

Main article: Medicinal clay

The oldest use of the term terra sigillata was for a special kind of medicinal clay from the island of Lemnos. People called this clay "sealed" because it was pressed into cakes and stamped with the head of Artemis. Later, it also bore the seal of the Ottoman sultan. During the Renaissance, people believed this clay could protect against poisoning and cure many bodily problems, so it was very valuable as a medicine.

In 1580, a miner named Andreas Berthold traveled around Germany selling a special type of terra sigillata made from clay found near the town of Striga, now Strzegom, Poland. He claimed it could cure every kind of poison and many diseases. He even let leaders test it themselves. In some tests, dogs were given poison and then the clay; those dogs lived, while other dogs given only poison died. Later, a prince tested the clay on a condemned criminal, who survived.