Lady and the T-shirt
ONLINE GUIDED INTERACTIVE SESSIONS
By Su Melo
hand - building
clay - firing - glaze
Firing is the act of exposing clay piece to high temperature to make it ceramic and be able to use it. To achieve this, you need a ceramic’s oven, better-called kiln.
There are different firing temperatures, it depends on the clay you use and the purpose of your new ceramic object.
In our courses, we use hand modelling Stoneware clay (high firing clay) 1230 Cº.
To have a better idea:
Terracotta and massive industrial ceramics are low firing clay, with a temperature range of 900 Cº to 1100 Cº. This ceramic is porous and it needs to be glazed to make it waterproof.
Porcelain, super high firing with a temperature range of 1230 Cº up to 1280 Cº (even more). It is almost like glass, that’s why it is a bit transparent.
Stoneware clay at this temperature it vitrificated itself and as its name says, it is almost like a stone. It means the ceramic has no porous and it is waterproof. This is why we see as an alternative and I suggest not to use glaze in our objects, but mostly because the process of firing is environmentally more friendly. No glazing consumes less energy and most of the oxides used to get the colors are toxic to extract and apply. This is why our clays have been selected by its beautiful colours to be able to show the color of the ceramics, also called naked skin ceramics.
Sample of clay we use is G&S number 592:
Even though, in kitchenware, is good to know the use of glazed has been considered as a hygienic measure. The glass layer makes the object easier to clean and it doesn’t stain from products like coffee or tea.
This is why we try to make a balance offering the chance to glaze our pieces. But having only transparent or whitish glazes (mate or glossy shine) and preferably applied only on inner parts of the pieces.
If you already have a glaze or want to use another colour, I can give you advice and see together where to buy it.