19 May 2009
Sometimes I still find it surprising how little I know about firing a gas kiln...it's not that I've had loads of experience but somehow, i guess i thought after 10 years of potting and firing gas kilns here and there with others, that the baseline knowledge would have been in my psyche somewhere...not so.
i have now fired my new kiln 3 times and from each i have gathered a tremendous amount of information. probably the most from my may 5 firing.
I had more pots than the previous loads so the stacking was a bit tighter but still only about 3/4 full. it seems that i have been under the gun each firing and am also so excited to get after it, that i have yet to fill her up. previous stacking had been too heavy at the bottom and very loose towards the top. i believe this has contributed to my uneven temps.
i had just been in n.d. for a week with potter girlfriends and fired a big kiln with power burners (i have 4 venturis) and we had a discussion about reading reduction out of the bottom peep...i had been relying primarily on the top for backpressure. this firing, i tried my best to get back pressure out of my bottom peep to no avail. i was reducing like crazy...i could smell it and was getting about 10 inches out of the top. what i did not realize is that reducing can stall out the temp which it sure did. it took me hours to gain 50 degrees but i just kept tweaking and waiting so the time passed quickly. only after i reviewed my log did i realize how freakishly long it took. i mean...at 4am, when i finally shut her down, i knew it was wayyyy too long and especially when i checked my propane tank and found i had used around 100 gallons of propane (ugh).
soooo.....i added another 2+ feet to my stack (picture above) and next time will chill on the reduction a bit. i did get beautiful shinos and my celadon was lovely. i need to figure out my temp/reduction unevenness though from top to bottom.
i reread a section in Vince Pitelka's studio book and noted the following tips for the next firing:
-no big adjustments to primary air (on burners) ( i was tweaking them a lot)
-when turning up the burners, open the damper slightly to allow things to equalize and then slowly close it
-cool bottom.... try damper out
-cool top.....try damper in
- at least 10 minutes of oxidation cleanup/clearing at the end. ( i had some bubbling and only cleared it for a few minutes) (again.....4 a.m.)
i'll fire again in a couple of weeks and update after....
07 May 2009
o.k...once a month posting is not going to cut it....especially when i have so many things to talk about. i think so much when i'm working and then wow is it tough to get in the blogging groove.
so my potting life has been a little more challenging as of late as i transition from electric firing and stoneware to porcelain and a gas kiln. there are so many things i love about porcelain but warping and plucking not so much. i made a bunch of cake stands that i loved and did not anticipate the drooping rims....i'm going to try to find a nice white stoneware that will work for handbuilding and cakeplates. i'm concerned about them matching my tea sets though so we'll see.
i drove to beach n.d. last week (11 hours) and had a mini workshop of sorts with 3 friends. i adore being with people who can stand to talk about clay and technical glaze/kiln stuff for hours. i don't get too much of that around here so it's a treat. we made pots, pit fired, glazed and fired in tama's big, beautiful car kiln. she and her husband run an amazing pottery business....we had many a discussion about pricing/who we're making out work for/ how to make a living...etc. needless to say, my prices will be taking a small hike.
i fired my kiln again this week. third firing and the most challenging yet. i swear the only way i learn things is by doing them wrong. no matter how much i read or who i talk to, it just doesn't sink in until i mess it up myself.
so i was shooting for heavier reduction, a faster firing and a more even distribution of heat work....stay tuned for the debriefing.
tonite i have an opening reception for 'chicks with wheels' the show set up was last week and i finally got most of my pots there last night....(see kiln saga post to follow). at this point, i was just happy to have some decent new work to show. thanks to my friend colleen's window idea, i was successful. my artist statement was a bit crabby and negative but that's exactly how i felt...sometimes the public thinks that we just play in our studios and 'how fun it must be..' i just wanted them to know that it's damn hard work and a lot of the time...not so fun. i toned it down a bit last night though so i won't seem like such a grump. (thank you to the gallery manager for letting me redo).
o.k....back to the shop to fill orders and make another kilnload of pots so i can fire again.