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Making Pots

Loading Pots

Firing Kiln

Unloading Pots

Report

Making Pots - May 2013

These were made while demonstrating during the Upwey Potters' annual exhibition.

Loading Pots June 2013

The kiln loaded and ready to fire.

A collection of Bill's mortaria and beakers, together with Laurence's bowls. Most of his were loaded in the back of the chamber.

The cones positioned to be seen through the spyhole. The 06 cone went at 1000C and ended up very melted! The 08 and 09 at 1250/60 were just about gone by the end of the firing.

Firing Kiln - June 2013

The kiln blazing away at night, this was during one of Laurence's experiments with over-stoking the fuel, resulting in massive reduction and flames sprouting from all gaps in the kiln brickwork and the top of the chimney. Spectacular but a bit of a waste of fuel and no way to increase the temperature!

The firing started at 11pm with a gentle pre-heat over night, with a few elm logs put in every couple of hours, the temperature rising slowly while everything dried out.

At 9am the stoking was speeded up and a mixture of elm branches and pallet wood was used to raise the temperature. We also experimented with the passive dampers, removing loose bricks from the base of the chimney to reduce the pull, so the heat was not sucked out of the kiln.

This shot shows the base of the chimney where the kiln shelf damper can slide into the gap between the chimney and the tunnel leading from the kiln chamber. The flames roar through this when the kiln has been stoked.

By 4pm the 06 cone went (at 1000C) and so a period of reduction was started, over-stoking the fuel and cutting down the chimney pull. The final results were darker than usual.

After an hour we started to raise the temperature again by burning more cleanly. This seemed a bit more difficult than the previous firing.

We tried a variety of stoking regimes and damper configurations. While Bill made pancakes Laurence managed to reduce the temperature by 50C !

We were using a new digital thermometer, which had proved out of calibration during use with the soda kiln, so were were aiming for a reading of 1150C which we hoped would actually be 1250C.

The temperature crept up until the cones 8 & 9 started to bend at about 3am. We finished firing at 4.30am with a clean burn.

Unloading Pots - June 2013

At 5.30am the next day the brick door was removed to reveal the fired pots.

Most of the pots were heavily reduced to a darker hue than previous firings.

The glazes were more mottled by the larger amount of ash.

Most of the glazed had matured and there were fewer cold spots than previously.

The cones can be seen - some bent over and some still fairly upright.

The back of the chamber revealed when the front stacked had been removed.

Laurence's teapots and goblets come to light.

One of many mortaria bowls, showing a very attractive mottling due to the more intense scatter of ashes.

Mortaria stacked after the bases had been ground flat where the seashell stands marked them.

Smaller mortaria, useful for beating eggs!

A bowl - missing the pouring spout.

A pair of jugs, the lefthand one was fired on its side, to see how the ashes reacted with the horizontal surface created on the upper side.

A stack of beakers after cleaning.

The Cornish Stone and Whiting glaze, stained with iron oxide, gives a dark brown, the ash adds a sparkle and hint of blue.

A wide bowl, glazed with Shiny White, a Bath Potters Supplies favourite with the classes that is enhanced by the fleck of ash.

Some of the beakers suffered slightly from the glaze crawling away from the inside of the rim.

These were raw glazed, with the glaze applied to the pot when leather hard. The clay tends to shrink more than the glaze which then becomes loose. Some were wiped and reglazed.

Another glazes was also used, from a recipe designed for raw firing, with a high clay content. However that can flake off sometimes as well.

This bowl had been biscuit fired before wood firing,so the glaze is slightly more solid and darker. It was put in the path of the flames coming into the kiln and so picked up more ash and a higher temperature. It had a lid, which warped out of shape during the firing, but luckily the shape seems to work without the lid as the gallery is fairly minimal

Report and Conclusions

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This firing took too long! The pallet wood had got damp in rain during the day before use and we did not get into a proper constant and regular stoking pattern - little and often is needed towards the end of the firing. It was also a fairly windless period, so the air was not moved as much as the previous windy firing.

The overall results were very good. The long firing produced more ash, so the glazes were more heavily mottled by that.

The metal firegratings that fit in the bottom of the fireboxes have started to corrode away, they were "repaired" by removing some of the less useful parts that just got in the way. That has increased the size of the grid and allows the embers to fall to the very bottom of the box before they have burnt away enough, that then builds up as a bed of embers rather than ash, which cuts down the volume of air that can be sucked into the kiln by the pull of the chimney. This may have contributed to the inability to raise the temperature as quickly as previously. These will have to be worked on before the next firing.

There were fewer cool spots in the kiln, with most pots getting a good soaking at the high temperature.

The need to unload Laurence's pots very early in the morning compounded the feeling of sleep deprevation, but they looked very impressive when on display in his exhibition later in the morning - hot from the kiln! Some pictures will follow.

We are off to the International Ceramic Festival at the end of June and look forward to seeing some other kilns firing, in particular Joe Finch's - who designed the blueprint for Woden.

Comments are very welcome - email Bill Crumbleholme

Thanks to :-

The team!