Mrs Morawa TPHS Ceramics What is Ceramics Ceramics is the art and science of making more or less permanent objects from earthy organic materials when they are subject to heat The elements gt EARTH WATER AIR and FIRE are all necessary in making ceramics ID: 624054
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Slide1
Introduction to Ceramics
Mrs.
Morawa
TPHS CeramicsSlide2
What is Ceramics?
Ceramics is the art and science of making more or less permanent objects from earthy, organic materials when they are subject to heat.
The elements > EARTH, WATER, AIR and FIRE are all necessary in making ceramics.Slide3
What is Clay?
Clay is different than mud… it is “plastic” or has “
plasticity
” – which is the property that allows clay to change shape without tearing or breaking. It will hold it’s shape.
Clay is an aggregation (composed of a mixture or minerals separable by mechanical means) of fine-grained mineral fragments.
Usually, it is made up of many different kinds of materials
Most of a clay body is made up of silica and alumina (and water)Slide4
How is Clay Formed?
Clay is a product of the weathering of the earth – due to the grinding of geology (water & wind).
Result of
Feldspathic
rock (in the earth’s crust) weathering and decomposing over millions of years.
See this video about how erosion creates different kinds of
clay > erosion and clay formation
Primary clay (Kaolin), Secondary Clay (Ball Clay), & Clay BodySlide5
Main Properties of Clay
PLASTICITY - The
property of clay that allows it to change shape without tearing or breaking
. When formed, it will hold that shape.
Numerous factors can make clay more plastic.
You can spray it with water.
You can store it in a bag with water.You can mix new plastic clay with the old.Slide6
Main Properties of Clay
SHRINKAGE - The decrease in volume of clay as it dries. Water weight and mass are gone when clay is dry. Shrinking happens in 2 stages – during the drying process and again during firing.
Some clays decrease in volume almost 20% during the shrinking process. Every clay body is different.Slide7
Stages of Clay Dryness
There are terms which describe the various stages clay goes through as it dries
.
https://www.youtube.com/watch?v=haVK_VkfCDk
SLIP – watered down clay, consistency of yogurt – “clay glue”
PLASTIC – good, working quality of clay, when it can be shaped without bending or cracking. Good for coils, throwing.
LEATHER-HARD – clay that has dried enough to be stiff but still contains some water. Clay can be carved and thrown pots can be trimmed at this stage. Stable – for slab building. Cool to the touch.
BONE-DRY – clay that has lost its physical water. VERY FRAGILE!
GREENWARE – clay that has been through the drying process and is ready to be fired in the kiln * clay can still be reclaimed
BISQUEWARE – clay that has been through the first firing in the kiln. It has not been fired to its mature temperature, but it has been made permanent. It is fragile and
pourous – and ready to be glazed. Slide8
Firing of Clay
BISQUEWARE can be glazed (*after first firing)
After piece has been glazed, the piece will be fired a second time – The Glaze Fire
This time, the piece will obtain the qualities of the fired glaze.
Many times this is a more glassy finish, but not all the time.
Ware can NOT be reclaimed after firing (BISQUEWARE OR GLAZEWARE. Clay that has NEVER been fired. Slide9
Preparation of Clay
WEDGING – the process of kneading clay to make it ready to use. Wedging serves the following purposes:
Removes air bubbles
Homogenizes clay – so it is the same consistency
Aligns the particles.Slide10
Firing of Clay
FIRING
–
heating pottery or sculpture in a kiln (or open fire) to bring the clay or glaze to maturity. Firing transforms clay (dried out
greenware
) into hard ceramic. We will be firing up to about 2200 degrees!
KILN – a special oven or furnace that can reach very high temperatures and is used to fire clay.Kilns may be electric, gas, or wood-fired.
More about the firing process later…