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" Woden" - Wood Fired Kiln - The First Firing!
This page records the first firing of the Woden kiln in January 2012. It is an archive of photographs taken during the preparation and firing.
The second firing archive can be found at this page link.
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Test Bowls - just thrown 70 odd bowls were thrown over the festive season 2011 and raw glazed when leather hard with different glazes to test how they behave. Some glazes cracked off as the pots dried, others worked OK. |
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There Be Dragons! Made by the Upwey Wednesday morning Sculpting group. Kiln Godesses were also made as votive offering to the flames. |
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Cabbage Fermenting Pots Niche Marketing gone crazy! Also a nice big bowl. The troughs around the rims hold water, which the lids sit in, thus forming an air lock to keep the bugs and air out, while letting the fermenting gases escape. Don't even ask why folk want to ferment cabbage, at least not until we try it!
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Multi-purpose vessels, with hints of Bronze Age about them. This way up they are serving bowls, the other way up they are cheese covers! |
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And so the first pots are laid to rest in the kiln! These are amphora, thrown in two parts joined together and handles applied. Also some of the famous Beakerfolk beakers. These have been biscuit fired then glazed with Cornish Stone and Whiting glaze, enriched with Yellow Iron Oxide (ochre), that turns dark brown in oxidising firings, but may be different in this reduced firing. |
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Close up of amphora and beakers. The pots are placed on sea shells, packed with wadding clay (a mixture of recycled clays and wood shavings). The shell acts as a non-reactive release surface, to raise the pots off the shelf and stop them sticking. They also leave a nice scar on the pot. Thanks to C-Quest of Upwey for supplying the shells.
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Jane Burden offers up her bowls and helps load the kiln.
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The second layer of the back shelf. The pieces are not packed too tightly, so that the heat can travel through the gaps. |
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The third shelf is mainly the test bowls. At the end where the flames enter the chamber from the firebox below we have placed pots that have been biscuit fired, rather than the raw glazes ones - because they will withstand the early heating better. |
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Bill stretches his knees out straight after a while kneeling on the prayer mat while loading!
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A view of the first five back shelves, showing the slightly staggered shelves and gaps aboves the bowls to encourage flow of heat.
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A close up of one of Laurence's tea pots.
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A closer view of the bowls.
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Bill lifting one of his bigger urns onto the top shelf. This was made at Corfe Castle in the summer of 2011, constructed from thick sections joined together in rings and then pinched out. |
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Dave Emery, taking a breather after loading the front shelves. There was a minor accident when Bill overloaded Dave with a couple of heavy ancient urns which toppled over the shelf while being positioned on the top shelf. Luckily the couple of collapsed shelves were rescued with only slight marks on the pots and a couple of write-offs. Lesson learnt about leaning without a firm footing! |
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The top shelf has a large Bronze age type urn, with a kiln godess ofering protection!
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The top right front of the chamber. The Venus of Villendorf looks ready to take a jump, but the dragon is settled for the ride! |
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A set of cones, used to see when certain temperatures are reached. They are formulated to bend at specified temperatures, viewed through a spyhole, from which a bung is taken. |
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A view peering into the top of the chamber, after the door has been almost bricked up.
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Alistair Hampson looks on and wonders if it will work!
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This is the cover over the main chamber door after it has been bricked up. It is an angle iron frame, filled with ceramic fibre, covered with aluminium foil held firm with wire mesh. The hole is cut so the spyhole can be accessed. Another smaller frame covers that hole. |
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Bill at First Light! 1300hrs 27th The gas burner from the Raku kiln sets the first logs alight!
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Early flames |
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3 chimney stacks These were erected "in parallel" to increase the effective cross sectional area of the flue. |
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A gentle heat, keeping the temperature at about 100C for the afternoon. 3" and 4" diameter elm logs burnt two at a time with a few bits of split log to provide some flames. These kept the heat going for at least half an hour. |
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As the embers built up the heat became more even and increased slowly through the evening to about 150C. The kiln and pottery inside are still drying out slowly. Over night the kiln was stoked every hour and a half with a few more logs, the temperature crept up to just under 250C |
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Early morning 28th January. The preheating is over and the real work is about to start. The panel that covers the door is ready to erect. Some pallets are handy for breaking up and using to provide a spirt of heat. |
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One firebox has kept going all night and new logs quickly started to burn. |
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The other firebox had cooled more and needed to be re-lit with a flaming brand from the other box. |
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Dave Emery arrives and carries out the first inspection! The digital thermometer was strung up with two thermocouples placed in ceramic sheaths at high and low levels. These simple wire thermocouples burnt out towards the end of the day, but gave a good indication of the rise in temperature. The pair of blue cased 38W floodlights were a very useful H&S feature at night |
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The smoldering log begins to burn through. |
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3 men pretending to be doing something useful in the sunshine! |
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Peter and Jane preparing an insulation panel for the back wall. The 25mm of ceramic fibre is cut to size and laid over an aluminium foil backing, with wire mesh support. The ends are bent over to trap the fibre and wire loops are fixed through to stop the fibre slipping too much. The panel is hooked up onto the tie bars to keep it in place. The panels were not placed until then to allow the wet kiln to dry out during the preheating period.
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The kiln was fired all day at a rise between 100C and 150C per hour. towards 900C the kiln was suffering from a heavy reducing atmosphere, as the flames were not getting enough air. It carried on as planned up to 1050, but when the attempt was made to change to an oxidising fire, it could not be acheived, even with the chimney dampers right open and the fuel changed to thin pine. Enter Luke with a petrol driven garden vacuum/chipper. This was connected up with a metal tube to blow more air into the firebox, thus promoting a fiercer flame. |
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This extra ventilation produced a positive pressure inside the kiln and the flames erupted from all the places it could. Jennie Hanrahan looks on amazed!
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The firebox at the other side from the blower leaked flames! Lizzie stands well back. |
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Bill tends the blower. The fuel burnt much faster and had to be restocked, but each time that was done the temperature dropped back, so the overall tise was slow. But the fire was oxidising. |
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Jennie checks the temperature reading. A cheer went up as 1200C was reached. |
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Laurence poking in more fuel and feeling the heat. |
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Laurence throwing sticks into the inferno. |
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Bill and Jennie hurling wood at the flaming mouth. |
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Dave Emery's home made digital thermometer - reading 1222C. The highest reading taken was 1233C. Then the petrol ran out in the blower, along with any enthusiasm to continue stoking (apart from Laurence who seemed to enjoy the fire!). So the stoking was ceased at 8pm and the fires allowed to burn down, cooling to about 1150C where a steady temperature was held for a while, until the mass of embers began to burn away. Then the dampers were pushed in to block off the chimney flue and slow down the cooling rate. |
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The chimney stacks were producing flames at the end of the firing. This is normal and part of the excitement. These 3 shortish flues will be replaced in the next firing by something with more pull, to enable a higher temperature to be reached more easily. |
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This is a view of the spyhole, with the ghost of a cone standing slightly to the left. The naked eye could see a few more of the cones in the same line, but we lost touch with which was which at the stage. |
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The late crew taking a breather. |
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The fireboxes were left to burn out over night, slowing down the cooling rate. The blown end was more burnt out. |
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The other end was full of embers that had been slightly starved of air while the blower was on. Now we wait a few days for it to cool enough to unload. |
Unloading Pots - Tuesday 31st January & Thursday 2nd February 2012 |
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We took down the bricked-up door and peered into the firing chamber, not sure what to expect! Worse Case Scenario would have been a melted pile of pots and shelves near the floor of the chamber - but we were greeted by the sight of the opposite = a stack of slightly under-fired pots. Bill puts on a brave face! |
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These large urns were unglazed and had turned a lovely toasty biscuit colour under the reducing effect of the smoky flames. |
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This close up of the set of cones shows the temperature had noot been high enough to melt the 1244, 1260 or 1280C cones. There is a fine dusting of ash over all of the horizontal surfaces and pots, but it has not started to fuse with the clay.
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This amphora was packed close to where the flames entered the chamber from the firebox that had not been boosted by the blower. The glaze has not melted as much as the other side, but the surface texture and colour is more than acceptable. |
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This is a view after the front shelves had almost all been removed. The 1260C cones can all be seen still standing.
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These glazed pots almost got hot enough. The larger urns are looking good. |
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A closer view of the mid height left back shelves. Laurence's tea pot sits there waiting inspection. The light blue glaze on the bowl below, which matures at a slightly lower temperature, has started to melt. |
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Dave Emery's jugs at the top right back of the chamber needed some more heat for the transparent glaze to flux. Alistair Hampson's urn is looking very ancient Greek! |
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The lower right back shelves got the hottest, with the blower rising the efficiency of the flue burning. Laurence's bowl has a nicely toasted outside, but the splatter glaze is still matt. Bill's two beakers at the bottom were used to drink coffee in celebration! |
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These bowls were in the middle height of the back shelf on the right. A few glazes have started to melt. |
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These on on the other end of that shelf. Not so hot... |
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This amphora is one of the better results, a lovely blend of reduction and flashes of ash, with an internal glaze that does the job. |
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Looking down on the bottom back shelf. The glazes at the right hand end where the flames came in were looking very close to mature. The other end was the coolest part of the kiln, with least reduction. |
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Close up of the hottest pots. These gave cause for hope for the future. |
There will be a report and statement of conclusions about how to improve the firing next time - posted here soon! Overall for a first firing we are fairly happy with how we got on. At least we did not overfire and ruin all the pots! Joe Finch's design is tried and tested and it is mostly our own silly fault for not getting it right first time! The first half of the firing was very smooth and easy, indeed Bill did some of it in his sleep! Getting up to above 1250C was always going to be a bit of an effort, we may have bottled out before trying to go that extra mile, but seemed to be fighting a battle that would not be won on the day, without better fire power! We are still discussing what to do next. We have plans to fire again in March and May - Dorset Art Weeks is a target event at which to launch the resulting wares at the end of May. Several improvements are needed to raise the maximum temperature. The gaps in the ceramic fibre insulation need to be filled to keep in the heat and keep out the cold air from being sucked in. Apparently we mis-understood the design of the firebox doors, there needs to be a 3" slot below the bottom door, through which the air is drawn into the bottom of the firebox, so that it travels along the length and rises up into the burning embers and wood, to promote more complete combustion. The iron grills we have near the bottoms of the fireboxes need to be altered so that the gaps are much smaller, thus stopping the embers falling through before they are burnt more. The chimney needs to be rebuilt using a wider, taller flue to give more updraught. To start with we will add some height to the flue, thanks to Peter and Jane's donation of some more steel flue. If that does not work we will dismantle the whole chimney and rebuild it. The timber needs to be split into thinner pieces, so that it will burn more efficiently towards the end of the firing. We will collect old pallets, they provide pine slats, which burn more quickly with longer flames than the elm. We need to get into a pattern of ritually stoking the kiln using alternate fireboxes. Doing it more often, quicker, with suitable sized wood. Maybe a fan could be set up for emergency use to boost the air intake. Comments are very welcome - email Bill Crumbleholme
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Thanks for help with this firing go to :- Laurence Eastwood Dave Emery Alistair Hampson Jane Burden (& Peter) Diane Crumbleholme Lizzie & Lottie Crumbleholme Jennie Hanrahan Bill's Pottery class students & the Wednesday Morning Sculptors for the dragons and godesses. C-Quest for the shells Everybody else who came along in person or virtually to offer support! The God Woden for not striking us down! Last not least Martin and Luke for being there and coming up with solutions and fixes, without being too abusive! |