Monday, May 5, 2014
How-to, A Teacher's Guide to Firing a Manual Kiln
Firing a manual kiln, A Teacher's Guide:
Preparing the kiln: Load desired cone into kiln sitter by lifting up the metal plate above the power button….
then pressing down the small lever to hold it in place- while holding the lever….
…place cone into kiln sitter on the inside of kiln and you can then let go of the lever as the cone will be holding it in place (be sure that when you load the kiln that your shelves are NOT resting on the kiln sitter- give it plenty of room). If using a cone (looks like a cone) make sure you load it correctly so that it will bend in the shape of a U when it gets soft (so that it shuts the kiln off). If using a bar (looks like a rectangle) you can load it any old way and it will be fine.
Make sure the timer dial is turned all the way up (turn to the right) so that your fire will not time out.
Candling overnight: I like to candle overnight if I am doing a bisque fire (not necessary for a glaze fire) to make sure work is completely dried out and to avoid explosions...
Explosions = broken hearted kids and extreme guilt, avoid at all costs! If things do explode you can bury them and pretend you are archeologists digging up ancient ruins… but seriously make sure the work is really dry before loading into the kiln!
So to candle overnight I prop open the lid using a kiln post and pull out all the peeps from the holes in the front of the kiln to let air circulate and to prevent the kiln from heating too quickly, thus causing things to explode if they are not 100% dry.
Then push the on button and turn all 3 dials to low. Turn on envirovent (the fan) if your kiln has one.
The next morning *** turn the timer back up (to the right) all the way so you don't time out*** Close lid (be sure to use a thermal glove because kiln post will be hot) and put back in the peeps (My pic only shows 2 peeps because the others broke off in the holes, so they are all in even if it doesn't look like it). Do not turn up the temp. By closing the kiln up it will build heat.
Wait 2-3 hours then turn all 3 dials to Medium.
Wait another 2 hours and turn all 3 dials to high. Let it ride. Kiln will automatically shut off one the cone bends in the kiln sitter.
Note*** I do not allow work that is over 1 inch thick into my kiln, however if you have any pieces that are thicker than one inch or more, you might want to let the kiln be on all low (with lid closed for 4 hours per inch) and the same at all Medium.
The two stages where you blow pots up are at the temp of boiling water (212 degrees) and when the chemical water is released at 1000-13000 and clay turns into bisqueware that can't be recycled back into clay. If you allow thicker pots to be fired, you'd want to give them a little more time at these two stages.
I personally wait to fire my pots until they are bone dry and then I still candle them overnight just to be sure they are 100% dry. As a teaching artist I prefer safe to sorry when it comes to firing other's work.