25 June 2009

another firing and a new glaze palette

so i fired my big girl for the fourth time last week...once again it was fun and exciting and longish and offered a billion new lessons.

i had 5 new glazes in the load and with such a big kiln and no super successful glaze base as of yet...i just make up 5000 gram batches (1/2 a 5 gal bucket) and go for it. it is challenging to glaze so many pieces (150-200) when you only have a vague idea of what it might look like.
in the last firing i had great success with a double dip on the outside/single on the interior, of m.davis shino so of course i loaded up on that....anytime that i think i have a glaze cornered enough to be moderately successful, i get burned. it fell off the pots in patches....all of them and did not blush in the dry spots (with the exception of 3 pots) so all of those went in the shard pile. at first i thought it was my lame dust sponging job but none of the other pots had glaze issues like that so i'm thinking it was the double dip not adhering.....my best guess at the moment.
i had also dinked with the bag wall which will be put back immediately.....first, the flames were shooting across the kiln instead of bouncing up and i also think it was the source of the larger than "normal" amount of brick dust that blew around and stuck in the bottom of many pots. i will vacuum out the brick gropple before every firing from now on.
i also learned in this firing that oddly enough....i had not been opening up the gas valves on each burner as much as i should have (thank you leif)....one of those things i had locked in my brain....i only turned up the gas until i couldn't hear/see any more effect on the flame and even though it was only 1/4-1/2 turn, i called it good. i had leif evaluate the burners and he cranked all of the knobs around an entire full turn....i almost fell over....it did kick it out of the stall and next time, i'll open those babies full up early on and see if i can fire in under 15 hours.
after overreducing and stalling out last firing, i tried to keep it in light reduction with a heavier one for 15 minutes around cone 9 1/2. i also cleared it out (oxidation/damper wide open) at the end for 10 minutes. the celadon was fair to good, yellow salt with turquoise did not overreduce and turn entrail pink ( i kept it to the bottom/front of the kiln) so that was good. the glaze tests were promising...just a little tempering of the turquoise, more sieving of the 2 cornwall stone glazes (bumps/chunks all over) and no more tan on the outside. as i sit here....i cannot recall what the victoria green stain looked like...yikes..i will run and check.
i don't know if adding a couple feet to my stack had any effect at all...i'm going to restack the bricks on the car bed to fit cleaner and perhaps a little of the door. i delivered all of the pots that were successful the day i unloaded before i took off for san francisco.
home now and anxious to fire again but must throw 200 pots first....better get after it.

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