Making Pots -

Another batch of Bill's cremation urns loaded in the car

More urns drying

Raw glazed mortaria drying out.

A batch of Bill's bowls drying after throwing and turning and decoration applied.

A dried urn.

Decoration by impressing a rope.

Snug fitting lid.

Bill's beakers being stacked in electric kiln for biscuit firing.

There is a problem with raw glazing drinking vessels - the glaze tends to clip off from round the rim. So biscuit firing them minimises that.

Raw glazed bowls.

"Maggot" impressed decoration, a cord spirally wound around a rope gives an impressed decoration similar to Neolithic round bottomed bowls.

The Iron Age style bowls have a lattice decoration applied by stroking a smooth stick down the shoulder.

All the pots finally dried! Ready for packing up and taking to the kiln for loading.

Bill got worried about not having enough pots to fill the kiln, with just over a week to go, so he knocked out a few more mortaria bowls.

In the end these were not needed as there was a last minute rush of pots from the classes and other potters. But they will keep until next time!

Loading Pots

Steve pallet breaking

After the first day, the back section is almost half loaded with urns in the cooler places and on the right side some biscuited pots that will get a blast from the flames and associated ashes.

After the second day loading, the back section is almost full.

Bowls and other pots, plus Caroline's sculptural ovals.

Steve capturing the pyro cones in an abstract way.

The guard dog.

The security guard patrol.

Spring has sprung!

The weather set fair, rolling countryside and nice dry pallet wood.

The back finished loading.

Cones in place.

End of the 3rd day of loading.

Just started loading the front section of the kiln.

The start of the last day of loading.

Almost full already.

Steve loading.

For some strange reason he bought some yellow glaze to try out. Maybe just to upset Bill's sensibilities?!

He mixed it on site and applied it onto dry unfired pots, so perhaps it will all fall off.

A close-up of the botonm front of the chamber.

Bill's urns looking good.

Close-up of top front of chamber.

One of Bill's beakers and Steve's "Death Mask" mug - this firing's "kiln god"?

Bill placing the final pyrometric cones.

Taking a breather before bricking up the door.

Quite a tight packing towards the top of the chamber, with the larger urns opening up the spaces at the bottom.

The left hand side flame entry path is narrower than usual, with bigger gaps horizontally between the shelves. Maybe the flames will follow a different route through the kiln?

Firing Kiln - 11th-12th May 2018

The firebox at 5.30am, after a night of slow preheating up to 400C at this point.

Using large logs - one put in each box every hour with a few smaller bits of timber to get those going - all the kiln and contents have been dried out, ready to fire more quickly.

Now onwards the fuel was scrap builder's timbers - up to 4" square, but mainly 2" or 3" by 2".

7am and all's well.

A good stock of nice dry pallet timber ready to burn, except for a few more pallets to break up.

The woodpile of builder's merchant waste and Nikki's friend's shed.

Not all of this was needed for this firing.

Steve's sculptural piece, made to keep an eye on the firing.

"Ned" was gently heated in what later became the pizza oven.

He was nicely dried out and did not seem to have broken by being heated so quickly from damp!

Luke playing with his new wings gave us a flypast.

I wonder if he felt a thermal lift from the kiln chimney?!

We must be getting superstitious! Mark's figurative offering to the flames.

Nikki "Catering Manager" with one of her pizzas fresh from the oven on top of the tunnel.

Another pizza goes in to be baked.

Cones seen through the spyhole at about 9pm, round about 1160C reading.

Smoke signals from the chimney top.

When fresh timber is put in the fireboxes it initially creates a batch of smoke as it ignites, together with a burst of gas, which pushes up the pressure in the chamber and the chimney. The smoke at the top shows that not all the fuel is being burnt completely - which is a waste, but it fairly quickly dies down.

During middle to end of this firing we tried to wait until the smoke had died away before restoking. Using smaller amounts of timber, but more frequently, trying to maintain a few pieces of timber in the fireboxes at various states of decomposition. That seemed to work well most of the time. The stalling periods were shorter than usual.

The firebox, now quite hot!

Nikki and Sarah taking a quick breather between stoking.

As the temperature rose the need to check the cones became almost obsessive!

A brick is removed from the door and the cones can be seen. The 8 & 9 cones used bend over when their melting temperatures are reached = 1270C and 1280C

If the spyhole brick is removed during a period when fresh fuel has been inserted the flames will curl out of the spyhole, in a rather miffic way!

The Cones are just beginning to bend at about 11.30pm, the digital reading was 1220C, but that is always showing about 50C lower because it is out of calibration.

The stoking continued to provide a "soak" for the glazes to mature and to allow some more ash to be picked up by the pots and glazes.

By midnight the crew was ready to leave after what appeared to be a good firing.

The stoking stopped and the doors were opened to crash cool the chamber down to about 1120C. That helps to keep the glazes free of larger crystals, which tend to make them cloudy.

Then the fireboxes were sealed up with bricks across the base gaps and the chimney was cut off with a sliding kiln shelf and the passive dampers removed from the base of the chimney to minimise the draught.

By 1am the cones as shown were well gone over and the crew left site.

Unloading Pots -

Steve removing the door bricks.

Looking Good! (The pots that is!)

Top of the front after the reveal.

The front uncovered.

Almost all the cones have gone over, but not too far.

Nice toasting effects from the ash, not too much reduction.

Bill's Urns. A great variety of tones, depending pon the amount of reduction, ash and temperature.

Some of these had Jennie's burnished pots inside, nestled in sawdust, but the smoke effect was not as desired.

Back of chamber revealed.

A good mature set of glazes.

The central column had shifted slightly, with a list to starboard, but only one pot kissed the adjacent shelf leaving a scar.

Perhaps it is time to invest in some more shelves?!

Another view of the rear of the chamber.

Bill's pots unloaded.

One of Steve's mugs.

Bill's urns at the back of the chamber.

Some of Bill's class's pots

Belinda's Lighthouse

Jennie's and her classes' pots

Anna's Casserole

Bill's urns.

Very pleasing!

Bill's mortarium.

The light oatmeal glaze worked as well as it ever has! Nicely satin finish, with no obvious pinholes and slightly melted surface, with sprinkle of ash specks.

More Mortaria.

A selection of Bill's bowls.

Various wares.

The Pie Dishes are Laurence Eastwood's.

Beakers and Bowls.

More beakers and bowls.

Bronze Age Style Beaker.

Dark brown "soup" glaze, with plenty of iron oxide and the residues of various glaze buckets (hence soup!).

The outside has no glaze below the rim, the toasting comes from the effect of ash reacting with the clay and mild reduction darkening the clay body.

The decoration was impressed with a comb.

Bill's Casserole.

Some of Bill's beakers.

This is the graph of the temperature over time, as measured by the top thermocouple and cheap digital meter.

It is out of calibration by about 50C at the top temperature, so the actual temperature was that much more than shown on this graph.

There are no really embarassingly long flat sections during the firing period, after the overnight preheat. That would indicate a "stall" in the temperature climb, which has been known to plague firings.

The last two readings are as the kiln was fast cooled before being clamped up.

These are the firings logs for various firings, superimposed over each other - with the most recent being darker.

This proves nothing?!

Report and Conclusions

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This was one of our best ever firings, in terms of reaching and maintaining a good temperature, getting well matured glazes and having attractive amounts of ash toasting on unglazed areas and speckle on pale glazes. The Light Oatmeal glaze achieved a lovely satin finish throughout the chamber, which points to an even firing.

The pyrometric cones showed a similar picture, with most of them bent, even those nearer the bottom of the chamber.

The team effort by the firing crew (with backup from the catering division) was brilliant, with a concerted attempt to keep the home fires burning constantly.

The fuel was a good mixture of logs and scrap timbers from pallets and builders' merchants. It was dry and broken and well sorted before the firing day, so there was no last minute physical effort involved - which can exhaust the stokers during what should be their rest breaks. The late crew were of the opinion that the thin hardwood shed timbers were better at raising the temperature than the softwood pallet timber. It was reassuring to have too much fuel in hand and to be able to put away larger pieces of timber not needed as the firing proceeded.

Helped by a different alarm clock and a more positive mental state of mind, Bill's selfless effort to stay awake from 5am meant the firing proper started earlier than usual and stayed ahead of the normal schedule compared to the clock, although the actual time taken for the firing was only reduced by a couple of hours.

There were no extended periods of the temperature stalling, although it did dip a few times, when concentration faultered - mainly thanks to the catering division producing excellent pizza.

Reaching Cone 8 at 11.30pm was good timing, with an hour and a half soak after that, several of the stoking team actually saw the end of the firing process, rather than leaving it to Bill to watch the fast cooling period at the end.

The chimney appeared to be drawing well during most of the firing, there were few flames issuing from the top of the kiln chamber, showing a negative pressure was in there.

The regime of waiting for the dark smoke to die away before restoking appeared to work well, with the fireboxes staying at the optimium level of timbers are various stages of combustion, not over or under fed. The lower firebox doors were opened more than usual, to allow more air in for combustion to take place quickly, increasing efficiency and wasting less unburn fuel up the chimney. There was far less observed flames exiting the top of the chimney than usual, indicating better burning in the fireboxes and main chamber.

The stacking was different than usual, in that there were more large urns in the bottom of the kiln, with bigger gaps around them. The top section was more tightly packed with smaller pots. There were no plates on racking taking up useful space! The front shelves were more spaced apart horizontally, which opened up gaps between them, allowing the passage of flames and hot air throughout the chamber. The gap at the lefthand side of the front stacking, where the flames enter from the firebox beneath, was smaller than usual, which might also have forced the flames into the chamber lower down as there was a restriction in the space vertically up the corner.

The temperature indicated by the low down thermocouple was much higher than usual, almost the same as the top thermocouple. Partly because the probe was placed a bit higher in the kiln and slightly more away from the side than usual. Also the larger urns may have allowed more heat to reach that corner.

Comments are very welcome - email Bill Crumbleholme

Thanks to :-

Fuel suppliers - Travis Perkins and Bradfords for pallets and scrap wood; The Winterborne Abbas Pallet folk; Nikki's freind for the shed etc; David, Mark & Paul for the logs.

Special thanks to Steve for breaking pallets during the loading sessions and also for behaving himself slightly better than has been known during the firing.

The Landlord for support and encouragement.

Pottery Class members and other potters for help filling the kiln and then firing and unloading it, especially because they had less of their own pots in the firing than usual, with Bill's wares dominating......