Wood Fired Kiln - Firing Log

ᚹᛟᛞᚨᚾ

" Woden" - Wood Fired Kiln - The Twenty-first Firing!

This page records the Twenty-first firing of the Woden kiln in November 2017. It is an archive of photographs taken before, during and after the firing.

No alterations were made to the kiln before this firing, except the addition of a kiln shelf construction added to the top of the tunnel from the kiln to the chimney, which worked very well as a pizza oven.

There was a problem with flames getting into the chimney without first taking a tour of the main chamber and maybe external air being sucked into the chimney. These fault will be check before the next firing.

Menu for sections on this Page:-
Making Pots	Loading Pots	Firing Kiln	Unloading Pots	Report

Making Pots - October 2017
	Prototype goblets - thrown for Bill's daughter's wedding in 2018.
	Sample urns for cremation ashes. The flat round knobbed things are the lids!
	Close up of urns
	Collared urn, with rope applied decoration - more was then added around the shoulder of the urn
	Urns drying out before going in the kiln. They are to be fired in the wood fuelled kiln without first biscuit firing and without any glazes applied so the colours will be due to the effects of the wood ash and the reduction of the iron oxides in the clay, which will darken the colour, in various amounts according to the intensity of the reducing atmosphere in different parts of the kiln.
Loading Pots November 2017
	Steve, earning his NVQ Level 1 in applying battwash to the kiln shelves - which protects them from attack by the ash and enables stuck glazes to be chipped off more easily.
	Steve applying glaze to some of his pots. Failing to achieve NVQ Level 1, because he spilt too much glaze and used too much blue glaze!
	Helen loading her sculpture
	Bottom of back of firing chamber, loaded with urns and Birgit's bowls. The collared urn lids have been placed on top of the urns, with the rim of the urn coated with release wash - 9 parts alumina Hydrate and one part china clay.
	Back of kiln almost full.
	Close up of Steve's deathmask book-ends.
	Back of chamber fully loaded, except for a few little fillers, test pieces and Steve's mystery objects.
	Finished loading the front section of the kiln. Cones positioned. Maybe a bit too tightly packed?!
	Bill with the first brick of the door.
	Pallet breakers and sawers. Many thanks to Martin with his chainsaw. The stock wood fuel is now a mixture - start with Kate's logs overnight; then old shed supporting timbers; then heavy pallet sections; then lighter pallet sections; then roofing batten acquired from a skip by Bill. Just in case, a couple of propane gas bottles and burners will be on hand to boost the final temperature push, if the team is unwilling to carry on beyond midnight!

Firing Kiln - 25th November 2017
	Lighting up time! 1700hr The preheat was started at 15.30hr - ahead of usual time. A chilly still evening.
	Kate's logs beginning to burn - each takes about an hour to burn away. Bill slept in the car for each of those hours overnight, getting up to put another log in each firebox. This image shows the support for the logs, a kiln shelf prop, with a smaller one inside, usually vertical between shelves. Unfortunately one broke and fell out of place, making stoking slightly more difficult and also opening up a gap from the firebox into the slot leading to the chimney - a short cut for the flames, which reduced efficiency. During this firing we tried hard to burn the pallet wood on its edge, which allows the flames to burn both sides at once and allow air rise between the pieces. If flat they tend to smother what is burning below.
	Around about midnight, all's well, after a pint with the landlord. Time for intermittant sleep. The temperature is kept about 250C for most of the night, drying out the kiln, shelves and pottery. From 0400hrs to 0800hr it was encouraged to rise to 350C.
	Morning has broken! A very fine day, if a bit chilly - 2C on car thermometer. The stoking continues, getting a quicker rise up to 800C by 1030hrs.
	While Bill went off to get some more food and stuff from home, Steve was left to tend the fire. He also made one of his "Death Masks" as an offering to the flames.
	The digital read-out from the top thermocouple probe at 1130hrs. Well on schedule. This cheap Chinese piece of kit is well out of calibration - a reading of at least 50C below the actual temperature. But we quote actual reading throughout these archives.
	Steve's offering facing the flames. Unfortunately it subsequently cracked up, because it was heated too quickly. It's spirit passed into the kiln?!
	Steve making another offering to the kiln. He claimed that this branch came from the sycamore tree at Tolpuddle, under which the martyrs met. Steve sometimes gets a bit strange when overheated or undernourished!
	A view at 1330hrs into the spyhole in the door, showing the two pyrometric cones. They should bend over when reaching the temperatures required to mature the glazes - 1260 to 1280C.. But this is still only about 1000C.
	Bill stoking. 1700hrs - about 1100C
	Steve stoking and looking, or is he praying?
	Or is he making a fashion statement in his new flame-proof overall (which he managed to burn through!)
	Evening falls. The temperature stabilises (i.e. gets stuck at the same level for hours!) between 1150C and 1180C.
	The joint between the brick of the door and the arch had not been made very well and flames poured out of the gaps when the pressure inside the chamber rose - each time new fuel was put in. There was a mat of ceramic fibre along the join, but perhaps the bricks above were not heavy enough to keep it pushed in place.
	Nikki, attempting achieve NVQ level 1 stoking certificate on her first attempt at wood firing. Doing well. The tunnel from the kiln to the base of the chimney had been converted into a pizza oven, by building a box of kiln shelves on top of it, with a couple of electric night storage heater bricks to provide a heat sink.
	Richard and Nikki having a heated discussion about stoking techniques.
	Richard extracting the cooked pizza.
	Richard stoking
	Nikki stoking
	Bill looking at the thermometer again.
	The cones, still upright.
	Bill stoking
	Richard demonstrating his ability to put his arm into the fire, or at least that's what it looks like from here. He may yet get NVQ level 5 stoking certificate, if he can come up with a couple more plausible reasons for the temperture not rising further!
	The pizza cooked very well, although the special plates (fired last time) needed oiling a bit more.
	Gazing hopefully at the digital readout, hope to see 1200C at the top and 1100C at the bottom of the kiln, at which time Nikki could crawl off home, her task acheived.
	1189.9C
	A surprise visitor was Laurence, who appeared out of the night on one of his walk-abouts from distant St.Ives. He came bearing news and advice. On his suggestion we opened the main doors of the fireboxes to let more air in and get the fuel to burn - which it did and the temperature rose to 1200C, but then plummeted back down to 1150C.
	Laurence dancing the Pallet Fan-dango - beaking pallets to earn a piece of pizza and cake!
	Richard stoking away.
	Still gazing hopefully at the temperature. And wondering "why oh why"....
	The bottom reading just reached 1100C.
	The top reading ever was 1207C.
	By 4am even Bill had got bored and with the cones just going over, time was called and the doors opened to crash cool the kiln down to 1100C.
	With the door open the large pile of embers at the far end of the firebox still took a while to burn away, even after a bit of poking with a long pole. That pile was probably not a good thing to have lurking in the kiln, as it reduced the air flow into the kiln at times and was not producing as much heat as fresher fuel, which at such high temperatures should vapourise without first turning to charcoal!
	The flames at the top of the door died away to a glow. At 1100C the kiln was clamped up, the fireboxes blocked up. The shelf slid across in front of the bottom of the chimney and the passive damper bricks removed from the base of the chimney.

Unloading Pots - November 2017
	Chamber door, ready to dismantle. Note very few black marks - so the flames were not able to escape through the gaps - we tried harder to minimise the gaps when building the door.
	Top courses of bricks removed to reveal well toasted pottery and a nasty looking accident where a kiln shelf had broken and pots fallen over - had this spread further down the kiln or was it just in that area?
	Jo's dragon and leaves - nice and shiny dark surfaces
	Top left of chamber - looking good.
	The middle collapse - only affected the shelf that broke and the pots below, but not too much damage.
	Top half unbricked
	The whole front revealed. Amazingly well matured, except for the bottom layers. Higher degree of reduction than usual, the pots are generally darker and the copper glaze has turned from green to red throughout the chamber, rather than just where close to the flames.
	Middle section close up. Caroline's gourd-like sculptures are looking well finished. Bill's goblets look great. The cones are not that bent at the very front of the chamber, but are well over at the hotter side.
	Half the front removed to reveal the back section.
	The back section revealed. Bill's urns are looking really spledid, with some beautiful tones from the ash and flames.
	Bird's eye view of Bill's lidded urns. All the lids were loose - treated with a wash of Aluminia Hydrate and Chione Clay 9:1.
	Bill's urn field!
	Steve's mugs
	Jennie's classes wares
	Sharon's wares. Light oatmeal glaze, picked up ash speckle but not quite as well melted as some previous firings.
	Steve's mugs. Fiord Blue glaze, highly fluxed by the ash, so that it runs down the pots very attractively.
	Bill's beakers and jugs.
	Caroline's sculptures. Glazed with a variety of found clays and ashes mixed into glazes.
	Birgit's bowls. Wax resist spots and Shiny White glaze.
	Bill's trade mark beaker. Very pleasing toasted unglazed exterior and nice darked brown internally.
	Jennie and Nikki sorting and checking the pots. Deborah's bowls in foreground.
	Bill's jug. Copper glaze, turned red by the reduction atmosphere.
	Bill's collared urn.
	Bill's jugs
	Bill's field of urns.
	An assortment of Bill's pots.
	Peter's tall vase.
	Bill's urn - lower in the kiln with less darkening reduction and shiny ash effect, but still very pleasing.
	Bill's collared urn. From the top of the chamber, with heavy ash looking almost like salted glazed ware.
	Bill's sample goblets.
	Bill's lidded collared urns.
	Lottie's pots.
	Mark's vase.
	Steve's bulbous vase.
	Steve's jugs
	Jo's dragon. A really well made and decorated piece, which has been enhanced by the firing.
	Steve happy with his bowl, copying Birgit's wax resist technique (but not so skillfully!)
Report and Conclusions	Back to top of page
A worrying firing at the time, with a struggle to reach and maintain a good high temperature. However the longer firing gave better reduction and shiny ash effects. There were few pots that were under-fired. The problems with the chimney were mentioned at the top of this page. These may have lead to a reduction in efficiency of the chimney drawing air through the fireboxes. There were more flames than usual coming out of the top of the chimney. The cones had gone over throughout the top half of the kiln and close to the flame entry positions. Trainee cone setter Nikki needs a bit more practice pushing the cones further into the clay stand, as a couple of them fell over rather than bent. The wood fuel was a good mix, roofing batten and fence/shed panels together with the usual pallets and Kate's logs. Everyone was very happy with their outcomes, with very few substandard pieces and some stunning objects. Steve will be getting delusions from this firing's results and may become commercially active! Please support a struggling artist! This a graph of the firing temperatures over time. Note that these are the readings at the top of the chamber, they are out of calibration by about 50C, so 1200 maximum is actually 1250C =- as witnessed by the pyrometric cones bending. Very slow pre-heat overnight; very quick rise in morning up to 1100C, then a period of "stability" when the temperature stayed between 1130 and 1190C for most of the night! This was the longest firing ever done -starting very early and finishing very late. 37 hours long. However the starting early just meant the pre-heat was longer, rather than speeding up the whole timescale. The kiln is known as a "fast fire kiln"! This is a slightly failed attempt at super-imposing the graphs for several firings, to show the trends. Comments are very welcome - email Bill Crumbleholme	Thanks to :- Kate V for her felled nicely seasoned logs. Buildrite and Winterbourne Abbas Pallet suppliers. www.onlineshells.co.uk/natural-cockle-shells-p-3855.html The Landlord for support and encouragement. Pottery Class members and other potters for help filling the kiln and then firing and unloading it, especially Steve, Birgit, Nikki, Sharon, Jennie and Richard. The NVQ certificates are in preparation!