Usually at a school you only fire the kiln to earthenware temperature.
so you would buy an earthenware clay.
firing is not about baking,
Its about slowly bringing the clay up to the temperature required to change it into a rock.
It has to go slowly to allow the steam to escape and also if you go fast the heat shock can make things explode.
LIke if you put a hot thing into cold water it cracks.
WHAT TYPE of clay DO YOU HAVE????
this is VERY IMPORTANT
the firing temperature relates to the type of clay you are using.
And the glaze also has to match the clay and the firing temperature.
I always recommend using earthenware clays in schools. the colours of the glazes are much brighter and if you use underglazes, these colours also remain brighter.
In stoneware ( 1260) firings, some of the colours 'burn out'.
The process
There are two types of firings the first is called the bisque firing and the second firing is called the glaze firing.
Bisque relates to the first time you cook something - think biscuit. A bisque firing usually goes to 1000 celcius for both earthenware and stoneware clays.
The glaze firing is a bit like baked on icing, its for the decorating stage.
The glaze firing can go a little faster through its cycle because all of the stem has already been fired out of the clay, but still needs to go no more than 100celcius per hour. Earthenware glaze is usually fired to 1080 and stoneware glaze to 1260.
Again make sure you know what clay you are using. If you fire earthenware clay to stoneware temperature it will most likely melt onto your shelves and kiln shelves are expensive.
BISQUE FIRING
The bisque firing is where you fire the work for the first time.
The work goes as greenware (which means not fired yet)
It needs to be extremely dry. It should not be cold to touch and if you scrape the bottom with a fingernail it should come off as a dry dust.
It is VERY important that the work is dry as most explosions occur when it is not dry enough. Claywork exploding will damage your kiln.
Basically it gets cooked like a biscuit, becoming bisque or biscuit. It is fired to 1000 degrees farenheit.
Everyone has a different idea about the temperature cycle but this is the one that i use.
Earthenware bisque
Take the Kiln up 50 degrees per hour till the kiln reaches 700
Then take the kiln up 100 degrees per hour till it reaches 1000
The bungs should be out to allow the steam and moisture to escape the kiln.
GLAZE FIRING
Earthenware glaze
Take the kiln up 100 degrees per hour ( no faster) till the kiln reaches 1080
Then let it soak for an hour ( this allows the kiln temperature to be consistent everywhere.)
The bungs should be left in, as there is no longer any steam to escape, and to conserve the heat in the kiln and save energy.
NOrthcote Pottery have a tip sheet about firing
here is the link
http://www.northcotepotterysupplies.com.au/uploadedFiles/1359935598578-5180.pdf
so you would buy an earthenware clay.
firing is not about baking,
Its about slowly bringing the clay up to the temperature required to change it into a rock.
It has to go slowly to allow the steam to escape and also if you go fast the heat shock can make things explode.
LIke if you put a hot thing into cold water it cracks.
WHAT TYPE of clay DO YOU HAVE????
this is VERY IMPORTANT
the firing temperature relates to the type of clay you are using.
And the glaze also has to match the clay and the firing temperature.
I always recommend using earthenware clays in schools. the colours of the glazes are much brighter and if you use underglazes, these colours also remain brighter.
In stoneware ( 1260) firings, some of the colours 'burn out'.
The process
There are two types of firings the first is called the bisque firing and the second firing is called the glaze firing.
Bisque relates to the first time you cook something - think biscuit. A bisque firing usually goes to 1000 celcius for both earthenware and stoneware clays.
The glaze firing is a bit like baked on icing, its for the decorating stage.
The glaze firing can go a little faster through its cycle because all of the stem has already been fired out of the clay, but still needs to go no more than 100celcius per hour. Earthenware glaze is usually fired to 1080 and stoneware glaze to 1260.
Again make sure you know what clay you are using. If you fire earthenware clay to stoneware temperature it will most likely melt onto your shelves and kiln shelves are expensive.
BISQUE FIRING
The bisque firing is where you fire the work for the first time.
The work goes as greenware (which means not fired yet)
It needs to be extremely dry. It should not be cold to touch and if you scrape the bottom with a fingernail it should come off as a dry dust.
It is VERY important that the work is dry as most explosions occur when it is not dry enough. Claywork exploding will damage your kiln.
Basically it gets cooked like a biscuit, becoming bisque or biscuit. It is fired to 1000 degrees farenheit.
Everyone has a different idea about the temperature cycle but this is the one that i use.
Earthenware bisque
Take the Kiln up 50 degrees per hour till the kiln reaches 700
Then take the kiln up 100 degrees per hour till it reaches 1000
The bungs should be out to allow the steam and moisture to escape the kiln.
GLAZE FIRING
Earthenware glaze
Take the kiln up 100 degrees per hour ( no faster) till the kiln reaches 1080
Then let it soak for an hour ( this allows the kiln temperature to be consistent everywhere.)
The bungs should be left in, as there is no longer any steam to escape, and to conserve the heat in the kiln and save energy.
NOrthcote Pottery have a tip sheet about firing
here is the link
http://www.northcotepotterysupplies.com.au/uploadedFiles/1359935598578-5180.pdf
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