Presentation on theme: "CERAMICS: BACK TO BASICS An Introduction to all things clay."— Presentation transcript:
CERAMICS: BACK TO BASICS An Introduction to all things clay
What is Clay? Decomposed rock called Granite Made of a combination of 3 things: Silica ○ Sand is made of silica ○ When heated becomes glass Alumina ○ A kind of flux ○ Lowers the melting point of the silica and clay Water ○ Physical water- makes clay moldable ○ Atmospheric water- water present in the air
Describing Clay Plasticity Describes how easily clay can be molded and hold its shape Clay Body Clay mixed with other ingredients to change the properties of the clay. ○ Properties include: color, firing temperature, degree of plasticity. Water management Need to control the amount of physical water in the clay. ○ In general: less water = the less plastic (less moldable)
The 6 Steps for Water Management Lots of Water Water and Clay Water is gone- only Clay left
Water Management- Steps 1-2 Slip Watery clay; at least equal parts of clay and water Used to help weld pieces of clay together Moldable Clay Just enough water so the clay can easily be molded and shaped Still has lots of water that can evaporate
Water Management- Steps 3-4 Leather Hard Still moldable but feels hard. Will break if not careful Bone Dry Green-ware Looks totally dry Only has atmospheric water in the clay
Water Management- Step 5 Bisque first firing ~1600 F Gets rid of most of the atmospheric water (started to chemically change the Clay-can’t put water back into clay) Makes the clay harder and shrinks some Makes it easier to glaze
Water Management- Step 6 Ceramic Final firing-Glaze firing Clay is Vitrified- permantly hardened Chemically pulled water out of the remaining clay Parametric Cone is a type of measuring system for ceramics Temperatures for final firings ○ High Fire clays ~2300 F Cone 10 ○ Mid Fire clays ~2100 F Cone 6 ○ Low Fire clays and Bisque ~ 1800 F Cone 04
Firing Clay Why do you need to fire clay? Makes clay less porous so it can hold water. What happens when clay is fired? Removes all of the atmospheric water Fuses the Alumina and Silica together Cannot become plastic anymore Where does clay get fired? Usually in a kiln which is a kind of oven Can also fire ceramics in a pit or open fire
Glazing What are the differences between Glaze and Clay? Glaze has more Silica and Flux Glazes also have more minerals and impurities to give it color. What purposes do glazes serve? Makes piece water-tight Sanitary-easier to clean Decorative
Applying Glaze to a Piece Step 1- clean off piece Step2- mix up the glaze- all sediments need to be mixed well Step 3- Apply glaze (thickness of a credit card) Dip- submerge and count to 2 seconds Paint- two thick, even coats Step 4- wipe off the foot of your piece anywhere clay will touch the kiln shelf cannot have any gaze because it will melt to the shelf!
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