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I’m   wanting  to do a test firing of a new porcelain body . Thought of just doing a one fire to see results

Am wondering if there  is a HUGE difference in results of one firing and  bisque & glaze

Thankyou Nicky

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A once fire is a bisque and then a glaze fire.  If you had a kiln load of once fire, you might duplicate the bisque schedule for the first 400 at least.  The only  real trick to once fire is the glaze application on greenware.  If you're only wanting to see the body, no glaze, go for it.  Be sure to run some shrinkage measurements.  Personally, I'd be bisque firing a bunch of test tiles if I wanted a new porcelain body (especially)

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2 hours ago, CactusPots said:

A once fire is a bisque and then a glaze fire. 

I thought a "once fire" is the same as a "single fire" --green to full cone in one shot-- no bisque first.  

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I should have said A once fire is a bisque and then a glaze fire ALL IN ONE FIRE.  What I was trying to say was that a single fire (once fire) goes through the bisque process and then continues on to glaze temps.  Doing a glaze fire with all bisqued pieces isn't doing much below the highest bisque temperature except burning off glaze water, wax etc.  You don't have to run bisque speeds.  A single fire needs to run bisque temperature ramps.

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@CactusPotsThank you for your input Getting  back to shrinkage Clay shrinks whilst drying Shrinks in one firing & bisque firing Is there more shrinkage at the glaze phase ? Trying to figure out shrinkages Just opened kiln happy with results ...... aside from shrinkage 

Thank you Nicky 

 

Edited by Nicky S

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Each phase of drying has shrinkage.  I know because of disasters I have had from each.  Mostly concerning larger pots.

To go to bone dry, I use a piece of newsprint under the larger pots to facilitate movement.

To bisque, I use a thin layer of grog under foot.

In a glaze fire, I use little blocks of soft brick under the feet, for runny glazes.  If the foot of the pot is too close to the inside edge of the soft brick pad, it can walk right off.

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If you're just firing a sample raw with no glaze, you do not need to do a bisque firing. Clay does very little to no shrinking during bisque. About half the total shrinkage is in drying, the other half in glaze, assuming you're firing it to full maturity in the glaze firing.

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