Sunday, May 6, 2012

We are firing the wood fired kiln!

It has been ages (must be about 2 years) since we fired the wood fired kiln and, as I write this, it is back in action again.
A quick peep into the firebox.

  After the fire box test that I mentioned last post, I demolished that one and also did major work on the kiln itself. I stripped out the chamber side wall lining bricks and replaced them, reconstructed the kiln floor, and built a new firebox...., much more sensible this time, but still with a step grate system, but much simpler and smaller than the one before.
Front row of work in kiln visible behind a small bag wall, built to deflect the flame upwards.  The two large pots are hidden behind the small work that you see on the shelves in this photo.  Access to load the kiln was easy with the firebox roof removed.

With the new firebox and work done to the chamber, this is in most respects a new kiln, and it will take me a while to learn to get the best out of it.

The firebox early in the firing.

For the time being, this firebox uses two kiln shelves, a thick layer of ceramic fiber, and some insulating fire bricks as a roof, but I would like to do something different later, as I really do not trust the kiln shelves.

I glazed a kiln load of earthenware pots, most had been previously bisque fired, but I also included two 26 inch high pots that were raw glazed.

Loading took most of a day, and a further day was spent tidying around the kiln, finishing the fire box, and preparing wood.

The warming fire made in a temporary add on firebox (note the cup of tea on top).

The firing started last night, with a three and a half hour warming up firing of the kiln to 100 Celsius (212F), to make quite sure that the pots were dry.  The fire was made in a little extension to the firebox that I made out of half a dozen bricks, and the heat from this was directed through the ash pit of the firebox.  It was simple, and pleasurable, to fire, and nice to sit out in the dark with the happy crackle of the burning wood.

If you look carefully you will see Nigella Stopit on the kiln roof.  Laura is sorting wood.  The kiln was at about 400 C (752F) when I took this photo.  Almost no smoke visible.

This morning I started the firing at 5.30am.  The kiln was still a little warm from the firing the night before.  This time I started the fire in the firebox itself.  A very small fire to start with, and then a gentle climb.  The step grate appears to be working well.  There was absolutely no problem starting the kiln with this firebox, both for the warming fire, and the firing today, and the flame is bright and clean with no unwelcome smoke to overwhelm  the stoker!

This shows the stokers view of the firebox.  Most stoking is done after removing the top insulating fire brick (at an angle with "Isolite LBX26" printed on it). Extra air can be provided by moving or removing the middle angled brick.  The lowest angled brick controls air to the ash pit.

The step grate does take a bit of getting used to, although I am quickly getting to like it.  Whilst navigating through the lower temperatures, there was always feeling that an unwise choice of wood or poor timing of stoking could have it galloping away.  However, it is good to feel that there is a reserve of power available.

I must go and check progress.  Laura has been stoking now from just above 500 degrees C (932F), and I guess we are around 675 (1247F) or so now.

Regarding wood firing.... it's good to be back!


gz said...

good to soee progress!

We have kiln shelves in the roof of the salt kiln I've been sharing. They last about six present we have a guard shelf above the work so that if the roof goes, it wont go far!

Hannah said...

Exciting stuff. Have fun.

smartcat said...

Wow! That first photo looks like a poster! I"d love to hear more about wood firing terra cotta.

Toes crossed that all goes well!

Amy said...

Wow- this is all so different- such learning for me! Sounds like things have been busy. how I wish I could be part of a wood firing closely here. All the best-

Peter said...

Hi Gwynneth,
I like the guard shelf under the roof of the salt kiln... it sounds like an air raid shelter! Salt is certainly hard on kilns and kiln furniture.... just six firings for the shelves that make the roof... really makes you think!

Hi Hannah, it was exciting and fun..., and I did keep wondering why it had been so long since the last firing of that kiln! (The crystal glazes have been quite a diversion). Unloading the kiln tomorrow...

Hi Smartcat,
Hopefully more firings will be happening soon. The terracotta work that is in the kiln should help me know where the hot spots and cold places were in the chamber, as the colour of the clay at different temperatures can read a bit like cones!

Hi Amy,
I wonder if there is someone in your area wood firing that would welcome some help around the kiln?? It would be nice if you were able to be part of the action. I like the way that wood firing makes the firing as much a part of the creative process as the original work on the potter's wheel was.

Joe Troncale said...

Can't wait to see pictures of the finished work!

Julia said...

Your wood kiln is beautiful! Can't wait to see the results of the firing.

Armelle said...

Really impatient to see the result of the firing :-)
Peter, I remember using the glaze I told you (my chün) on a low iron clay, and I did get a white glaze. This glaze was blue over a rich iron clay.
Best wishes

Peter said...

Hi Jo, Julia, and Armelle,
Lovely to hear from you all, I notice that your comments all have something in common.... "Can't Wait", "Can't wait", "Impatient..."! Therefore, without further delay, I will do you a great kindness, you will now find another post with photos of the pots that came out of the firing! Best Wishes to you, P :)