Firing Lots Of Bisque In One Load

[oldlady]

last year we had a discussion about firing lots of bisque and then using it in several glaze firings.  there are many new people now so i thought i would post today's firing containing some of  the bisque pots i will be packing up to take home and glaze.  there are 27 of the ones i call cracker trays, the longer ones, and 27 butter dishes.  plus lots of small items, leaves and some of the larger big-ticket items.  there are 5 molds in this firing.  i do them in raku clay so they resist cracking.  yes, virginia, pots can be stacked on top of each other.  this firing was to cone 04 minibar in a sitter.

[Joseph Fireborn]

Ah the joys of a white clay. I am testing tumble stacking my brown stoneware. I stacked a few unimportant pots to see if I get pinholing due to lack of burn out. If not then I am going to continue testing the boundaries of it. I would love to use only 1 or 2 shelves and tumble stack the kiln slap full for bisque. I will find out soon though, aka tomorrow evening when I open it up and see if there are pinholes in the pots.

 

Old Lady, you make a lot of trays! Must be a good seller, beautiful work.

[glazenerd]

Lady:

Obviously you have discovered the economics of bisqing larger loads equals money saved. Some clays will allow it and others will not. I tried that with stacking porcelain tiles: the most I ever hit was three high before fissures formed. I sawed most of my tile setters in half so I can stack tile vertically in bisque firing. I have fired 270- 8 x 10 tiles in my larger kiln in 32 setter sections. I did the whole firing at 160F an hour with a 20 minute top hold. I takes nearly 30 hours to cool off with that much thermal mass. One thing about large loads; not wise to push it.  Like the patterns you used.

Nerd

[Pugaboo]

Wonderful oldlady! You have been BUSY. I've mentioned on the forum before that I tumble stack as well. Beautiful pieces with lots of interesting textures and patterns. I have found that tumble stacking makes it take longer to cool as well, pretty close to double the time to cool. It's so worth it though to get so much work in there saving money and time in the future.

 

T

[MatthewV]

I personally have never observed any problems from rather chaotic stacking. This includes putting a plate on top of a vase or balancing large vases on each other.

 

There are issues with cobalt, copper and to a lesser extent chrome staining nearby pieces. People working with underglazes should avoid stacking too.

 

I personally load the most fragile pieces at the bottom, carefully fill the space around them efficiently as possible, and then use a shelf. Saving the weird fragile piece to the end runs the risk of "if I move this mug just a smidge more I could get one more small... ooops" moments from happening. On a similar note of efficiency, small pieces are free filler to fit in the wasted space.

[MatthewV]

Some software developer could make a "kiln stacker" Tetris style game. :-)

[Roberta12]

After having read about tumble stacking here in the past, I started really loading up my kiln.  I haven't had any problems with either stoneware or porcelain. I do a slow bisque.  I don't stack up the yarn bowls though.....I try to keep them from warping.  But I do fill them with small things.  I bisque to o4. 

 

Roberta

[Roberta12]

And Old Lady??  Beautiful trays!!  I love the patterns and textures!!

 

Roberta

[oldlady]

thanks, all.  i used 6 full size and one half shelf.  i fire one switch per hour, takes 9 hours and the firing went off at 1am on wednesday.   i unloaded it friday afternoon.  the pots were warm but not so hot i needed gloves.  two of the mold forms have tiny cracks.  i rolled clay into each form and ran back to the nursery to get more leaves to do another one.  they are not really tumble stacked, just fully loaded shelves with short posts except near the sitter where i used 4 inch posts. 

 

i remember being new and putting only a few things in the kiln at a time.  of course, that was 112 clay.  would never stack it.

 

Terry, can you tell which pattern came from the red dress?  the other odd ones were placemats.

 

Evelyne, thank you again for the cats.  i added cocktail glasses and a clock showing 5 o'clock in the background.