Blog from Alan HopwoodHopwood's Recollections
"When I recall my childhood I realise that I spent a lot of time around bottle ovens. When my father was demobbed, I was 7 and spent a lot of time around bottle ovens because he repaired and rebuilt a lot of them around Burslem. At that time they had been unused during World War II and the linings had gone, and were in need of re-lining. I spent a lot of time with him, once even holding a bottle oven up on tree trunks while the bottom was taken out and replaced. So you might say that I spent 10 years around bottle ovens, seeing how they were made and then working them as a oven 'oddman' now and then, until I was 17. Written May 2016
Work on a PotbankI was 17 at the time when I did such work [on the potbank] but Don Carpentier (now deceased) thought that I was something special, just because I had shovelled coal into the mouths of a bottle oven as a matter of my routine work in the 1950s. All that I was doing at that time was trying to earn a living and only acted as oven 'oddman' now and then. Mr. Durber, an expert in his job, was forever passing his knowledge on to me as we worked. He was like an encyclopedia of bottle oven firing and it was a lot to take in. To me at that time it was a waste of time for rows of bottle ovens were dropping like ninepins to make way for the new tunnel kilns. All that I have is the experience and memories of doing that kind of work. I don't profess to being an expert. Written April 2015
Bottle ovens - building and repairWhen under construction and repair a lot of them [bottle ovens] collapsed. Of course in those times they didn't have ‘accro props’ and such like. My father once held a bottle oven up with steel girders and pit props whilst he took the bottom and the lining out of one at the Crownford works along Blake Street, Burslem in 1946. He was lucky. When somebody else tried it, it fell down into itself. Written April 2015
Bottle ovens - efficiencyWhen they were being fired it was all 'seat of the pants' stuff. On a 10-mouth oven we used to get through 40 tons of coal over 72 hours, some times more when firing a lot of flat ware to biscuit.
I would say that most of the heat went into heating the saggars. Then another waste of heat was letting the smoke out of the bags which then went straight up from the fire mouth and out through the top dampers on the dome. If a bung of saggars fell and crushed a flue there was a wasted fire so the 2 mouths each side of the flue were drawn up to try and compensate for the dead one to minimise loss. Strong winds drew fires to nothing. Yes, I have to agree, they weren't very efficient. Written April 2015
Problems in the ovenWhile the kiln was being worked, all flues would have had a fireclay plug or a half inch thick metal plate over them. [This was to stop rubble dropping into the flues and blocking them up. A blocked flue in a bottle oven could signal a massive failure since the hot gases would be unable to circulate throughout the setting.]
In my own experience, we were firing an oven and heard a thump and straightaway fire shot out of the corresponding fire mouth. The fireman [responsible for the firing] did a lot of swearing and said “We've got trouble now! That's a bung of saggars falling across the flue pipe.”
If you're half way through the firing process and a firemouth becomes half choked, this affects three fires - the one which is choked and one on either side of it. In a case like this you have to draw the choked fire as best you can then overdraw the other 2 to try and keep a good heat in the affected area.
The experience of that fireman was such that we were successful in firing the problem oven with very little ware needing a refire. That old man learned me a lot in a few months - it will keep you in good stead.
Those were the days when bottle ovens were falling like ninepins. Written May 2016
Downdraught OvensThe usual downdraught kiln was a 'beehive' shape with 10 fire mouths and a free-standing chimney, a few yards away. Then there were a series of flues going underground from the beehive to the chimney. At the bottom of the chimney was a big firehole.
This type of kiln was quite devilish to get going. A good fire was made up in the chimney so as to get a good draught through the flues from the beehive itself. Then you lit the fires round the beehive but as I said before it was quite sluggish at first. All the heat in this case was collected in the dome and was then drawn down through whatever wares were being fired, through the flues and across the yard to the free standing chimney.
I wouldn't like to guess what the temperatures were in these kilns but when one looked through the spyholes the light inside was more silver or even electric blue, instead of gold to white as in an updraught kiln. Written May 2016
Firing the OvenOn firing a bottle oven we used to fire up to about 90C and then slow down for three hours to raise the temp to 350C this was to allow all the chemically combined water elements to escape as slowly as possible. After this we used to aim for [a temperature rise] not more than 100C per hour up to 1200C this was to allow for the fact of the wares being inside saggars which were a good 1 inch thick this probably gave a firing temp 1050-1100C which was held for about 20 minutes. This according to the fireman, was to allow the wares to "have a good cook."
Blog from Julian ReadRead's photos of the remaining ovens, April 2017 Julian Read FRSA is a runner in his spare time and says "I actually took photos over the weekend of 8th and 9th April 2017 and ran 3 routes carrying my camera. Just seemed a good idea and appears to have gone down very well." He wanted to record the condition of the remaining bottle ovens in The Potteries. Some were in good condition, others in seriously bad shape. Photos here > in What's Left?
Bottle Ovens by Kenneth Quinn2nd September 1975
My first-hand experience of bottle ovens was when working for five years as a youth at Johnson Bros., Hanley, including nights spent fire-watching during the war. I know of seven types of oven, divided between updraught and downdraught.
1. Updraught hob mouthed - fed from the top, [of the hob] with the chimney stack rising from the shoulder of the kiln, so that no cold sir is drawn in.
2. Stack oven - built together, often several under one roof - they smoked back badly when first lit, filling the shop. They were hard to repair and slow to cool.
3. Skeleton oven - late nineteenth century, the stack supported by arches, with a space of 3" to 7" between stack and oven walls. A door for cleaning out the stack was provided in the stack side above the top of the oven.
4. Hovel oven - as at Gladstone - the mouths protected from wind, easily repaired, but little space for firing.
5. Downdraught - for biscuit, late nineteenth century, also used for bricks and tiles.
6. Minton and Robey Patent - the ﬂoor had connecting flues to a deep flue to the chimney which served several ovens. The oven also had a flue but the crown damper was closed when the even was hot.
7. True downdraught - Wilkinson type - with bottom flues to upward flues in walls - expensive to build and needed frequent repairs.
A typical oven floor had a labyrinth of flues, with dual and contradictory purpose - to provide a smooth fast current of hot gases to the central well-hole (so to heat the middle of the oven) and at the same time to delay the passage of hot gas sufficient to heat the floor. In the Gladstone fireboxes there are three holes at the back - the centre one leads directly to the well hole, whilst the outer two lead into the labyrinth which goes partly to the well hole and partly to the side flues.
The well hole is usually constricted by the fireman with oddments to prevent over-firing in the centre causing pinched end warped ware. The flues must be kept clean and their clearness can be proved by putting a lighted candle in the well hole, to be seen from the fire mouths. The floor of the kiln is made of interlocking "natched" bricks.
Looking up inside the kiln you will see the crown hole,‘ about 18" diameter, with a damper with linked rod control to close it. Halfway between crown hole and oven sides are four oblong holes plus two smaller square holes each - known as cooling holes or ring dampers, with levers to close them. when firing a biscuit oven, the cooling holes are kept closed except during the early "water-smoking" period up to 250 degrees C, then closed until they are used to accelerate cooling at the end.
For glost oven cooling the dampers are opened thirty minutes before the last trials are drawn, and left holes. The small holes are smoke holes. This sharp cooling of the glost oven gives a clear shining glaze.
The shoulder of the oven has a small hole over each fire mouth, thought to be air inlets to the oven top - they could be used to adjust for bad firemouths. Bottle ovens were unstable as between firemouths - a good firing mouth attracted more draught, emphasising its superiority over a badly drawing mouth. Three Gladstone ovens have three trial holes - the oldest has four.
In Longton, drawing of the fired oven was done by casual labour - men seeking this work assembled outside Longton Town Hall at 6am, and the potbank undermanager would engage the best team he could choose - often miners on short time. A team comprised oven men, step men and carriers. Large works had their own t earn. The oven men, and step men had a beer money bonus - the practice of casual labour continued until the 1950s.
The official temperature allowed for men to enter an oven was maximum 120 degrees F except four times a year, a regulation obviously open to abuse. _Men did work in very hot ovens in the 1950's, with sacks over their heads and shoulders - Mr. Quinn: quoted a description by Enoch Bradshaw in the Potters Examiner of 1844 of drawing conditions stating that the first evil was "drawing hot" - ovens fired at 6pm drawn at 6am next morning.
The oven staff comprised, fireman, sitters-up (for night watching), cod-placer and placers. Biscuit saggars would be only sanded. together, but glost saggars were wadded with clay. A placer's pay was about the middle rate - in 1871 a placer as paid 5½ days at 5/- = 27/6 per week. The 'oddman' built up the clammings, punched. out clinker etc.
The Gladstone is producing a leaflet on bottle ovens for school parties etc.
Noted by Rodney Hampson
For definitions of unusual Potteries words go to The Potbank Dictionary here>