Thesis Firing Round 1: Soda Kiln

UAF Soda Kiln October 7, 2014

I finally had a chance to fire my favorite kiln again, this time for a large portion of my thesis work.  Despite the fact that winter is now upon us, and there's no going back once snow hits the ground in Fairbanks, it's bundle up and fire baby (at least it was only 20 degrees)! The following images document the process; from glazing, to loading, to firing, and the most exciting part, unloading!

Lots of bisqueware waiting for their coats of liquid glass.  

Mugs for my thesis coffee service set.

Bottoms up! When I glaze these cups, I like to layer and accent the slip inlay designs with various colors of glaze.

So once the glazing is done, we need to do some prep work for more technical aspects of the firing.  

This lovely mass of material is the wadding.  It's a 50/50 mix of alumina hydrate and kaolin.  In the soda kiln, we have to "wad" the work, which means that we make little balls out of the wadding and glue them to the bottom of the pots so they don't become glazed to the kiln shelf.  

These are the cone packs that we used to help determine the the temperature and evenness of the firing.  Each cone is designed to bend at a particular temperature.  There's a row of "low" cones which help determine when body reduction happens, and a row of "high" cones which we use to determine when to spray the soda ash in the kiln and when we've reached our peak temperature and shut the kiln down.   

Once that's done, we can load up the pots, wadding, and cone packs to take out to the Experimental Farm where all the fun kilns are located!

Wadding all of the pots to be loaded in the kiln. Helpful tip: line your tables with newspaper so the wadding doesn't stick, or in this case freeze, and break off the pots!

Loading the pots in the kiln.  We use three supports, which seems a little odd perhaps, but it's actually the most stable way to stack the shelves.  We make "donuts" with the wadding to go on top of the support to help alleviate any warped or bowed shelves and to ensure that we can level all the shelves. Other donuts may have been involved too.

Back stack all done!

Almost there! We put the cone packs in the front stack, one on top and one on the bottom.  

Once we're done loading, we put in the door.  When we do, we want to make sure that we can see the cones through the peep.

And done! Tomorrow we fire!

Now we're ready to fire the kiln! This kiln is designed to fire with two fuel sources, the first being wood to get the kiln hot enough to ignite our second fuel source, used veggie oil donated by local Fairbanks Princess Riverside Lodge.  If you'd like to read more, check out this blog post from August.

A few of the most outstanding UAF students helping to fire the kiln. 

Sending smoke signals. This black plume of smoke means we're in reduction, ie there's more fuel than air to burn it.  Because the excess fuel doesn't completely burn, the kiln atmosphere becomes filled with free carbon.  These free carbon atoms will grab up any extra oxygen molecules and produce the very unique surfaces and colors that are specific to reduction firing.  

Once the cones tell us we're even and up to at least cone 8, we're ready to spray in a soda solution.  It's a 5lb 50/50 mix of soda ash and baking soda (two different forms of sodium bicarbonate) dissolved in water.  The sodium vapor combines with the silica found in the clay body to form the luscious sodium silicate glaze. 

We let the kiln "soak" after we've sprayed the soda in and then shut the kiln down.  The next part, waiting to unload, is the hardest.  Luckily for you, you've been spared this painful wait.

It was a very Merry Christmas! Lots of great pots from this firing!

..and of course everyone's least favorite part..clean up! But hey, that just means we get to do it all again! We have to scrape the shelves of any soda build up to ensure a decent lifespan for these silicon carbide shelves.

Hopefully the kiln wash won't freeze!