Thursday, April 3, 2008

More Thoughts on Soda Firing

After reading the previous post, my good friend and former studiomate Mary Jo Schmith, of Front Avenue Pottery and Tile in St. Paul, Minnesota, offered her thoughts on soda firing, along with some photos of her soda-fired work:

FYI...I fired with soda for 2+ years here at the shop. I tried many different ways of introducing soda in to the chamber, including dumping it in the bag wall with an angle iron rod full of soda bicarb. I finally used a sprayer because
It did NOT leave large chunks of soda on the pots
it did NOT leave large chunks of soda on the kiln furniture...which stinks!!
It DID give the very best distribution of soda thru out the dry spots.
Using a regular garden sprayer
4 1/2 lbs baking soda dissolved into 2 gallons hot water in the sprayer
start spraying at cone 8 bending
Spray into each port 12-15 seconds each port.
I think I went around the kiln 2 or 3 times & then waited for cone 9 to bend.
Start spraying again at cone 9
again at cone 10
Keep spraying until all liquid gone.
I drilled 4 new ports into the kiln walls.
one on each side of the kiln, just above the top of the bag wall and about 1 foot away from the burner port.
one on each side of the kiln door, just above the top of the bag wall.
I also sprayed into the peep holes in the door...the ones used for cone spy.
Total of 6 ports to spray in.
The placement of spray holes was clearly to spray soda solution in to the bag wall/flame so the solution would flow with the flame.

The brass tip of the sprayer will most likely eventually melt off so always had a spare tip, including the entire replacement wand!!!

I started with 4 1/2 lbs baking soda PLUS 1/2 cup salt but stopped using the salt entirely because it made the pots dark...dark brown, rather than gently flashed with color.

I also tried placing pots full of soda bicarb around the kiln chamber on the shelves with the pots. This was not all that successful at creating surface BUT DID make a huge mess on the shelves, ruining them!!!!!!!!!!!

Here are a couple more images:

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