Why Single Fire?
Have you ever been caught up in a rush of
creative energy while shaping a piece, and lost that feeling while
you waited for the piece to dry and then be bisque fired?
When you look at the bisqued piece, does in seem
lifeless and divorced from when you were shaping it? Does it feel
like glazing is some totally separate process that is very
difficult to unify with the forming process?
Do you hate the way bisqueware sucks the liquid
out of your glazes, making runs and drips twice as thick as the
rest of the glaze coating? And when you do brushwork does this
sucking property thwart your attempts at carefully controlled
Do your high clay content glazes shrink and crack
on bisqueware and then crawl away from the cracks in the
Do you love the feel and control of painting with
acrylics or oils where your paint glides off the brush and mixes
predictably with previous strokes?
Would you like to compress your production cycle
into half your usual time?
Would you like to use about a third less energy
in firing your kiln?
Would you like to cut your kiln loading and
unloading in half, while still producing the same amount of
The more of those questions to which you answered
"Yes", the more reasons for you to look into single firing.
George Lewter from cone6pots.ning.com has started a
single fire interest group. If we can get a committed group
together to study the single fire process somewhat systematically,
we will likely progress much faster than if we work individually in
isolation. With a dedicated group we would also have a better
chance of enlisting the aid of one or more established experts.
- For a preview of why you might want to do something so radical,
electric glaze firing page at centerstreetclay.com Steven
Hill's Website. He has been single firing for some thirty
- Basically, single firing involves glazing your pieces when they
are in the leather hard to bone dry stage. You need to use high
clay content glazes that will shrink similarly to the clay body to
which they are applied as both the body and glaze dry out. Firing
has to be very slow in the initial phases to allow moisture to
escape slowly from the body and through the glaze without
separating the two. After the unbound water and the water of
crystalization are driven off, the rest of the firing cycle can
proceed pretty normally for the glaze effects you are trying to
- Single firing is not some Johnnie-Come-Lately, hare-brained
invention. It has been used commercially for many years, glazed
bricks, roof, floor, and wall tiles, toilets, and ceramic plumbing
fixtures are all typically single fired.
Here are some links to photographs of single
- These are gorgeous pots by
Gertrude Graham Smith. They were salt fired to
cone 10, so we won't be able to duplicate this look in
our cone 6 oxidation firing. This is just a sampling of
- I received an email from Ellen Fisher
as to her firing range, and she's doing low fire terra cotta,
single firing with commercial low-fire glazes. So the technique is
valid across all clay firing temperatures.
If you are ready to dive in then you'll need some
techniques. You won't be able to use those glazing tongs on
leather hard clay or on greenware.
- Richard Aerni had an article on single firing in the Dec 94
issue of Ceramics Monthly which you can read at his Website. He's
talking about ash glazes reduction fired to cone 10, but his
discussion of glaze mixing, combinations, and spray application
apply equally to our work at cone 6 in oxidation.
An Obvious Combination for Single Firing
would be to paint a leatherhard piece with colored slips, and
then glaze it with a suitable clear single fire glaze. I haven't
found a lot of ^6 raw glazes, but here are a couple quoted from the
Marek & Pauline Drzazga-Donaldson on fri 10 mar 00
I have developed a once fire cone 6 glaze from the basic Leach cone
10 - 11 glaze.
Cone 6 Based on Leach Clear/Transparent Oxidised
Potash Feldspar 40
Flint (Quartz) 25
Whiting (CaCo3) 20
China Clay 12.5
This gives a really good shiny surface and can be quite thick and
does not run. You could add 2.5 of Bentonite to make it up to
Cone 6 Raw or Once Fired Glaze. This glaze can be painted on very
Potash Feldspar 38
Flint (Quartz) 20
Whiting (Chalk) 32
Ball Clay 10
This glaze acts in similar manner to the first. Can be applied
thick, takes oxides well, very stable over a wide range, does not
run. If this one works for you let me know. It really is a
stallwart for me.If you give it a really good cone 6 -7 then it
will pool nicely. Happy potting Marek http://www.moley.uk.com