While #amphora has been making its entrance into the cellars for a few years, we are also seeing different materials making their appearance: #stoneware, #earthware, #porcelain, #ceramic, #clay... enough to get lost in it!
A quick look at the terms:
ℂ𝕖𝕣𝕒𝕞𝕚𝕔𝕤 𝕒𝕟𝕕 𝕔𝕝𝕒𝕪 Word of Greek origin: keramos means "clay". The generic term "ceramics" refers to all objects made of earth/clay that have undergone an irreversible physical and chemical transformation during baking at a higher or lower temperature.
Ceramics and clay are therefore generic terms that designate a large family.
𝕋𝕙𝕖 𝕕𝕚𝕗𝕗𝕖𝕣𝕖𝕟𝕥 𝕔𝕖𝕣𝕒𝕞𝕚𝕔𝕤:
Stoneware, Terracotta, Porcelain, as well as #earthenware, belong to the family of ceramics and are therefore not interchangeable. Each one has very different physical and technical properties. They differ in a number of related aspects:
Composition - The presence of silica (a major component of glass which allows vitrification during firing) allows a higher or lower baking temperature and influences porosity and micro-oxygenation.
Baking temperature - This is the delicacy of ceramics, you have to bake at the right temperature and the right time, like a cake! Baking too high will cause the pottery to crack or break, baking too low will cause oozing and permeability. The presence of silica makes it possible to fire at a higher temperature.
Porosity - High temperature baking with silica causes a vitrification process which reduces the pores and therefore limits intrinsic micro-oxygenation. A lower temperature baking opens the pores and promotes micro-oxygenation.
Finally, ceramics would be "the vine", clay would be the vine stock and stoneware, terracotta, porcelain... would be the grape varieties.
The terracotta is baked at about 1020°C. The pores of the clay are not completely closed and the micro-oxygenation is strong (more than a barrel). The porosity is between 6 and 10%.
Stoneware is baked at over 1300°C due to 70% silica. It is a very resistant material, easy to clean and the pores of the clay are closed. Micro-oxygenation is reduced. It is an insulating material, used in the aerospace industry to protect rockets from the outside temperature when passing through the atmosphere. It is therefore not very sensitive to temperature differences. Its porosity is less than 2.5%.
Porcelain is baked at up to 1400°C and is completely vitrified thanks to its high silica content. It is exceptionally pure and crystalline and has a porosity of 0%.
Thus, choosing the right amphora starts with choosing the right material!
Below is a table summarising the different ceramic bodies that you can also find in our catalogue, along with other explanations such as the millenary history of these ceramics.