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" Woden" - Wood Fired Kiln - The Twelfth Firing!

This page records the Twelfth firing of the Woden kiln in October 2014. It is an archive of photographs taken before, during and after the firing.

No alterations were made to the kiln before this firing.

The weather was warm, fairly windy at times, but with at least a gentle breeze. Some rain.

The timber fuel was mainly offcuts of kiln-dried building battens and other planks (from Bill's nephew Simon) and some wood donated from building demolitions (including some massive rotten oak timbers from Bill's studio) and a few branches and twigs, but with no pallet wood!

Menu for sections on this Page:-

Making Pots

Loading Pots

Firing Kiln

Unloading Pots

Report

Making Pots - 2014

 
 
Raw glazed Jug

Raw glazed Jug

 

Raw glazed jug and jars

 

raw glazed bowls

Raw glazed bowls

 

raw glazed bowls

Raw glazed bowls

 

Biscuited Beakers

Biscuit fired beakers

 

Black Burnished Ware bowl

Close-up of bowl inspired by Iron Age Maiden Castle War Cemetery Bowl.

Loading Pots 2014

 

Back of kiln loaded

The back section of the kiln chamber loaded.

Front loaded

The front section of the kiln loaded.

Laurence happy

Laurence happy to have finished loading the kiln.

Ready to brick up the door.

 

Firing Kiln - 18th October 2014

 
Night firing

The daytime heating went smoothly, no photos taken!

This was taken at about 9pm, when the temperature was just about 1250C, but it now needed a "soak" to help mature the glazes and allow the bottom of the kiln to warm up a bit more (it is always slightly cooler than the top).

Door open

By now the flames were very intense when the door of the firebox is opened!

 

Flames

The flames issue from the fireboxes when the door is open.

All the sparks are pieces of small ember that will float with the flames through the kiln and land on the pots, each piece creates a small patch of colour on the pot or on the glaze.

Laurence Hot

It is hot work stoking the kiln at this stage!

 

resting

So sometimes you need a quick rest!

 

Flames from gap

After stoking each piece of wood into the kiln, there is an increase in pressure as the vapours are produced when the wood incinerates, that rise forces the flames out of any gaps in the brickwork of the kiln, the unburnt gases feed on the air and burn. The rest of the time the pull up the chimney keeps the pressure in the chamber lower and so air is sucked into the kiln through the gaps.

 

Cones

The spyhole brick is removed so the pyrometric cones can be seen. Here they are bending over as they melt, the righthand one bends at 1250C and the lefthand one at 1280C. Although they may go a bit earlier if heavily reduced or if fired over a longer than normal period of time.

They are still more accurate than the digital thermometer, which is out of calibration.

Watching cones

Watching the cones can become a bit of a fixation, but it is not good for the retina!

 

Watching cones  
Cones

Here the cones have finished bending - the tips are resting and cannot bend any more. Although sometimes they can melt into a puddle, which is a bit worrying!

 

Pyro reading

The digital thermometer reading 1230.9C

The highest it reach was 1240C, which is the highest ever recorded.

The actual temperature is about 50C higher, according to the cones.

Bill firing box

Almost midnight and the ghost of Bill watches the final wood burning away.

The final fire must be oxidising, not reducing, to improve the sparkle on the pots.

A quick cooling of a couple of hundred degrees helps to freeze the glazes before too many crystals can form and make them milky.

The fireboxes are closed up and the air gap below blocked with bricks and the chimney is sealed off.

Then the long wait before the gtrand opening - usually 36 hours later.

 

 

Unloading Pots - 2014

 

Laurence examining

The front exposed, having removed the bricked up door.

Laurence is examining some of the pots and cones. A very exciting time!

Top fired pots

A close up of some of the pots at the top of the front section.

Well reduced and nicely toasted with ash.

Helen's blob

Close up of Helen's sculptural blob, with one of Laurence's bottles.

Note the completely collapsed cone, showing a good high temperature was reached, even in this fairly cool part of the kiln chamber.

Back fired

The back section of the kiln chamber.

A great result, with great urns and jugs and some nicely toasted bowls and beakers.

Emma's cracked plates

The major problem in this firing was a curse on plates and bowls made by Emma, many of which cracked.

Several of Laurence's pots broke in a similar way and a couple of Bill's.

Plates do tend to flex somewhat during high temperature firing, these were press-moulded and so are not as strong as thrown wares.

This was the highest temperature firing done so far, it may be that caused more warpage, which eventually leads to breaks. Bill's pots tend to be more robustly thrown (i.e. thicker!) so are less likely to distort.

 

Urns

A collection of urns, mostly made at Corfe Castle in July by Peter Woodward and Bill.

pile of pots

 

A pile of fired pots.

The beakers were especially good, the internal glaze being a beautiful shiny brown and outsides a variety of hues from pale biscuit to darker shiny textures.

The large bowls were fired stacked inside each other, some were fine, but a couple flexed out of circular because of the extra weight on the supporting shells.

beakers and bowls

A close up of some of the beakers.

 

bowls

These bowls, inspired by the local Iron Age wares, were glazed with Gunmetal glaze, resulting in a satisfying slightly matt dark finish.

A band of latticed marks round the upper side gives them a special appearance.

 

 

Report and Conclusions

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The firing was uneventful!

Started at 7pm on Friday, Bill kept it slowly heating up overnight, 300C by midnight, 400C by dawn.

7am saw the start of the proper firing, constant stoking up to 1000C by midday, it stuck a bit at 1050C. Got to 1100C by 5pm and 1170C by 7pm. On Laurence's return from visiting the sick, by 9pm, the cones had started to go. By 10pm they were gone enough, by 11.30pm it had had a good soak, with the temperature readings between 1170C and 1240C at the end, the thermocouple probe was found to be slightly pulled out of the sheath, so earlier reading may have been lowered.

So a well behaved stoking, keeping up a steady stoking with a reasonable built up of embers seemed best. When the embers were raked - to enhance the amount of flyash landing on the pots - the temperature seemed to fall afterwards.

Using dry wood helped - some was a bit damp, but had been dried off by stacking next to the chimney for a while.

The results were mainly very pleasing, although there were some breaks and distortions because of the higher than usual temperature. There were no underfired glazes!

Comments are very welcome - email Bill Crumbleholme

 

Thanks to :-

Crumbleholme Builders for the timber offcuts.

The Landlord and sons for support and encouragement.

Pottery Class members for help filling the kiln.