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Gas Kiln: The First Firing

Gas Kiln: The First Firing
This is a picture of my husband, Ronnie, and I with the gas kiln firing and in reduction!!!  It was our first effort firing a gas kiln, so we were pretty stoked that we could get it firing, into reduction and up to temperature!

To begin with, I decided to do a first firing of my fibre-lined gas kiln to cone 5 (mid-fire) as I have unfortunately used a variety of clays and due to my lack of record keeping can’t remember what types of clay I used (rats!).  As I knew that some of the clays are mid-fire, I didn’t want to chance taking them too high and the cone 5 will work for all the pieces.  Much of the clay that I “inherited” when I purchased the gas kiln was mid-fire, so it was good to see how it fires.

I decided to only mix up two mid-fire glazes, both Greg Daly glazes-MF 20 & MF 26.  So not much of a selection, but it is safe!  I decided to spray most of the pieces, as I was trying to make the glaze go as far as possible as I only mixed up 1000 grams of each.

My first job was to pack the kiln and although I’ve packed electric kilns, I had never packed “my own” gas kiln-very exciting!

The bottom shelf was huge – as wide and deep as the kiln – and I completely filled it with lots of small, short items.  This proved to be a mistake as the low shelf with another right on top of it, didn’t allow for enough air flow, thus resulting in under fired pieces on the bottom shelf.

So, the kiln is packed and I’m good to go!  I now know (hindsight) that I should have waited til I had a full kiln load, as firing half a kiln load is inefficient, but also the firing is not as good.  Also, I made the first shelf very low and that is a no-no!  I’m learning, ok!?

A funny, little clay kiln god came with the kiln, so I fed him some Twisties (Aussie Cheetos) and shut the door.

The set-up for the gas burners coming into the kiln is really inconvenient.  My wonderful husband, Ronnie, was such a help as you have to light the gas torches from under the kiln.  Both openings are on the bottom of the kiln, at the side, with the chimney at the back of the kiln -perhaps a poor design?

Lighting the kiln was easy – much like lighting the pilot light on a hot water heater or gas dryer-yes, I’m showing my age here!  The thermacoupler at the top of the gas torch must be in the flame and get hot enough to keep the flame going or it will go out.  So we were lit and cooking!

We had to be constantly crawling around on the floor to look at the burners!  Pretty much tortuous for me!  So….Ronnie came up with a genius idea!
By placing a mirror under the kiln, directly under the burners, we could see the flames and what was going on!  Brilliant!  Also, this is Samantha Scout, our wonderful pottery dog!
This pic shows the mirror and the view we had of the burners – which worked great!  I was afraid that the heat would be too intense for the mirror, but it was surprising cool under there.
As I wanted to try for reds in this firing, we started reduction at 850 degrees Celcius and maintained that til we turned it off.
The kiln got up to 1192 degrees which is about Cone 5, but we could never reach 1220, which I was going for.  After 11 hours of firing, I called off the firing and we turned off the gas and closed up the kiln.  All of this was done with lots of reading, but there is no good step-by-step manual for firing this kiln.  I did try to go by the firing schedule that came with the kiln when I bought it and also used the firing schedule in Oriental Glazes by Bailey (see page 17 & 18- Look inside for “A copper red glaze firing”).
The hardest part of any firing is NOT opening the door too early!  So the kiln is shut tight!  This kiln wouldn’t close tightly due to broken clasps, so my husband devised a clever clamp system to shut it and keep it closed tightly.  I managed to wait til the kiln cooled to 200 degrees C before opening it!
Here is the kiln as I opened the door.  Not bad!  Nothing blew up!
But…as I said, the bottom shelves were too close together, without enough air space between.  Another mistake was not using enough cones or enough cone packs.  I later learned that I should have them on each shelf, front and back, until I learned how my kiln fired.
Here are the results of the firing.  There were a variety of clays used, but only a couple of glazes.

I did get some reds!  Wahoo!  Reduction on the otherwise copper green glaze!

Many of the pieces could have used more glaze.  The results even looked a bit “wood-fired” as the clay got a nice toasting in the reduction!

Written by Marian Williams

6 Comments

  1. Joe Dan · January 19, 2012

    Wow that is some great work Marian! I really like it! I like the blog too…for sure! haha love where you and Ronnie were crawling on the ground! lol classic

  2. Jean · January 19, 2012

    Oh Marian! The pottery is just beautiful! You inspire me so much! Makes me want to quit “thinking about it” and start “doing it”.

  3. Beatrice Nathan Pottery · January 26, 2012

    Really great blog thanks for sharing! I’m sure you know this but just in case ceramic fiber is dangerous to your health and you should always wear a mask and gloves when handling it and make sure to thoroughly wash any skin or clothing that comes into contact with the fiber.
    Best,
    Beatrice

  4. Marian Williams · January 26, 2012

    Hi, thanks for the comments! Yep, I do know to be very careful around the fiber kiln. I normally wear a mask at all times – just didn’t wear it in the photos. It works great and I’ve heard rumours they are outlawing them in some locations-yikes!

  5. Vinkee · February 17, 2014

    Great Blog ,Marian…how about if you could share some experiences using Electric kilns and your choices about it.

    • Marian Williams · February 19, 2014

      Hi! Thanks for your comments! I use an electric kiln for bisqueing my pots. I used to fire to cone5/6 for glazes in an electric kiln, but have always dreamed of firing with gas/propane because the results can be so much fluid and dynamic. I now have that opportunity!

What do you think?