Terracotta shard with brushed white slip

You can see the action of the brushstrokes on this piece of terracotta, which instantly takes my imagination right back to the person who originally painted it. It may be a white clay ‘slip’ that they have brushed on, known as terra sigillata, in which the particles have been ground to nano-size. When baked on, it forms a smooth and much less porous surface, useful for this purpose, the fragment is probably an old sewer-pipe.

Terra sigilata was used in ancient times. It’s only very recently we have figured out what’s happening at the nano-scale, and can call it nanotechnology. It has also been taken internally throughout history as an anti-poison medicine.