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

This page records the third firing of the Woden kiln in May 2012. It will be an archive of photographs taken during the preparation and firing.

The problem of reaching a high enough temperature in previous firings has been tackled by rebuilding the chimney with a brick stack 5m high, instead of using the stainless steel twin flues. Buildrite Ltd, our local supplier have supplied a batch of Class B Engineering bricks, which look very similar to the Gloucester Golds, but have more smaller perforations rather than just the three larger holes. A mortar recipe suitable for kiln chimneys has been recommended as 10 lime/30 sand/1 cement.

Menu for sections on this Page:-

Making Pots

Loading Pots

Firing Kiln

Unloading Pots

Report

Making Pots - April/May 2012

 

 

Beakers

Beakers

A batch of Bronze Age Style beakers, raw glazed with Cornish Stone & Whiting transparent glaze, with yellow iron oxide - which will turn dark brown in the firing.

The simple thrown shapes are enhanced with impressed decoration, done using a wooden comb to build up herring-bone patterns of zigzags.

Mortaria

Mortaria

Mortaria

Platter

A collection of Mortaria, based on Roman shapes.

They were used for grinding the food and then serving it.

They make useful functional bowls for modern living!

Building new Chimney & Loading Pots 17th May 2012

 

Laurence Bricklaying

Laurence is trying to remember how to lay bricks, he did a quick course at college, but does not seem to be any better than Bill!

The chimney has been designed with a series of twists and leans, which are following the advice of a Patagonian wood firing potter whose website suggests that a perfectly upright chimney will not produce as much up-draught as one with a twist, however in the northern hemisphere our twist is of course reversed.

The stepped tapering of the brickwork restricts the cross-sectional area as the hot air accelerates upwards, thus maintaining velocity and the pull of air into the kiln.

 

Passive dampers

The "passive dampers" at the base of the brick stack, these are pairs of tapered bricks that can be removed to allow air into the chimney, thus cutting down the draught. This adjustment is made during the reduction phase of the firing, when the timber is starved of air which produces a smokey flame that seeks oxygen - removing it from the clay and glazes to produce darker hues and flashes of colour.

There is also a kiln shelf that can be slid across the opening into the chimney, but using that to cut the draught causes turbulance which is less stable. But that is used at the end of the firing to close off the chimney.

Topping out

Laurence tops out the chimney, trying to find the bubble in the spirit level!

 

Laurence loading his teapot

Laurence is looking happy about his latest teapot, now being loaded.

Back shelves loaded

The back shelves of the kiln, now loaded up

Front of loaded kiln

The front shelves, with some guest potters' work.

Firing Kiln - 26th May 2012

 

Stoking

Starting the final push, after a night of preheating up to 150C, then a day building up to 1100, with a period of reduction.

By 8pm, the fire is fierce and needs feeding every couple of minutes, alternately in each firebox.

The new thermocouples, thank you Peak Sensors, worked well to show the rate of increase of temperature, but were out of calibration, so the pyrometric cones bent over at 1250C, but the digital reading was only 1180C.

Chimney Flames

The new brick chimney worked very well, producing much more updraught that the previous steel flues.

This shot shows flames coming from the top of the chimney - not a particularly necessary feature, but very pretty! This shows that some of the gases were not completely burnt inside the kiln - only getting finally enough oxygen when reaching the atmosphere. This tends to happen when new pieces of timber fuel are thrown in, as they start to burn a lot of volatile gas is given off, which needs more air to burn, which is not available, this gives a good reducing effect, which we are happy with.

The new chimney brickwork did crack in places, as it expanded with the heat, but the angle iron frame keeps them in position.

 

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Flames

A close up of the firebox, showing the flames produced by the burning wood, new pieces quickly burst into flames and turn to charcoal and the embers fall through the grid and then they burn out to end up as ash on the floor of the firebox.

Resting

Resting! Laurence and his trainee stoker, Connor, take a quick break and watch the flames. The cones have bent over and we tested how the fire burns with the doors open at different positions.

A good oxidising fire could be achieved by opening both the doors and piling the fuel in. For an hour we tried to keep the temperature as high as we could without too much effort!

Unloading Pots - 28th May 2012

 

We are awaiting copies of photos taken by Maggie Cooke during the unloading on Monday night.

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Fired Pottery

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These are some photos of the wares that came out - although some were sold during Dorset Art Weeks before being recorded here!

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Bill Crumbleholme Wood Fired bowl

Bill Crumbleholme Wood Fired Bowl.

A reasonably large serving bowl, nicely textured and toasted, with a light oatmeal glaze inside that has picked up a speckle from the fly ash.

Bill Crumbleholme Wood Fired collared urn

A collared urn, unglazed but enhanced with impressed comb decoration and heavily reduced to a pleasant dark tone (sounds like a real ale!)

Bill Crumbleholme Wood Fired 3 beakers

A trio of beaker drinking vessels, sturdy little mugs that are a pleasure to quaff from!

Bill Crumbleholme Wood Fired amphora

One of the amphora, fired on its side, with a good ash speckle.

 

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Report and Conclusions

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This firing was much more sucessful with the new brick chimney. Most of the wares were fired very well, with some great flashes of ash and heavy reduction. Perhaps not so much ash as when using the blower previously, so perhaps we need to stir up the ash bed a few times to promote more flying ash.

The fuel burnt more effectively and it was less effort to increase the temperature. The elm logs were satisfactory, even at high temperatures - as long as they were split thin enough. The pallet wood certainly burnt fiercely, but a mixture of the two seemed to work well.

There were a couple of cooler spots in the kiln, particularly the corners away from the paths of the flames and perhaps where the gaps between the shelves were not high enough for the currents to get into the far sides.

Bill's beakers and urns have been much admired and sold well during Dorset Art Weeks. Guest potters Armin Hermann and Jane Burden have also sold their work then.

Bill's work will be on sale during the summer and beyond- see the events section of this website.

Comments are very welcome - email Bill Crumbleholme

 

Thanks to :-

Everyone who helped and encouraged us and put their trust in us by bringing pots to fire.

Thanks to Connor for joining the stoking and unloading team.

Thanks to Dave Emery and his contacts for the supply of pallets.

Thanks to Buildrite for supplying the new chimney bricks (and more pallets for fuel) and Peak Sensors for the new thermocouples (3mm diameter 2m long)

Thanks again to Luke and Martin for putting up with us.