What is terra sigillata and what does its name mean?
Terra sigillata translates quite literally as sealed earth and plays an important role in the history of ceramics. It has been around since around the 1st century and is a very distinct type of Roman pottery (although this technique was also used by the Greek). The word sealed in its name actually has two meanings. Firstly terra sigillata is actually a very thin slip that is lightly brushed onto pots to seal them when fired, meaning you don’t have to glaze them afterwards.
Secondly, sealed can also relate to stamping, as the pottery was heavily decorated with a stamp design in Roman times. The kind of themes of painting that were developed on the bodies of the work often either depicted erotic or mythical scenes or activities like hunting.Its name is often shortened and called terra sig for short.
Terra Sigillata is also known in archaeological circles as Italian decorated tableware, which had been made at the time of the Roman Empire, their colouring ranges across all spectrums of terracotta, oranges and reds.
Taking the process further in the late 1st century, the French used a very similar technique called samian down in Gaul. Their colouring varied with deeper red and pink slips, but they still bore the traditional intricate stamped decoration from floral motifs to depictions of animals on their dishes and bowls. African slipware did not develop until around the 4th century.
What are the benefits of using terra sigillata?
The slip that is used for terra sigillata is made from a very refined clay and the effect when the pot is fired is a thin glaze which can be very shiny when polished after it comes out of the kiln, in fact terra sigillata is one of the easiest ways to burnish you work.
One potential downside is that it can be tricky to obtain a completely smooth finish applying the slip by hand with a fine brush, as it is extremely thin and can show marks on the pot up easily.
How can it be made?
You can quite easily have a go at making your own terra sigillata and need only a few items; clay, water and a deflocculant. A deflocculant is basically used to repel electrical charges in clay particles, therefore breaking up the clay more easily. The deflocculant that Ceramics Arts Daily recommends to use is Darven 7 or Darven 811. Mix your deflocculant with water in a large plastic bottle and then add your dry clay. If you don’t use ball clay, you can even use clay body scraps. Shaking the mixture thoroughly is imperative, then leave it to settle. You’ll see how the deflocculant works as all of the sludge will sink to the bottom of the plastic bottle. The tricky part is getting the middle layer out of the bottle to use; you can do it by cutting a slit in the plastic bottle. Make sure you don’t get any of the sludge with it. Your pot should be very clean before you apply the terra sig, and it’s best put on with a very thin glaze and a wide fine brush. A few coats will be needed, although the pot will need to dry between coats.
Buff it up with a cloth afterwards for a beautiful burnished finish.
What other techniques can be used with terra sigillata?
Terra sigillata and raku firing go hand in hand. Raku firing is when pieces are removed from the kiln when they are burning hot (without going through the cooling process) and then put straight into something combustible. The patterns and rich colours of the terra sigillata glaze once it’s been put through a raku firing are striking. Another idea is using horsehair to make brilliant patterns. All you need to do is get your terra sig pot out of the raku kiln and lay horsehair over the piece, and it will burn incredible patterns into the surface, which can look a bit like marble.