No two are the same

No two bottle ovens or kilns are (or were) were alike. They were all built differently, many (almost all) without any architects drawings or plans. They were built 'by eye' and based only on the experience of the builder and the verbal requirements of the factory owner.

They all had very different 'characters' and their firemen (the men who were responsible for firing the oven) had to learn how best to work with them, to control and cajole the way they were used, performed and fired.

But all ovens had one distinct and common feature, their bottle-shaped chimney stack, whether round or square at its base, or whether bulbous and shapely or straight sided and just a simple cone.

All bottle ovens were described as intermittent since the firing process occurred periodically, at regular (and sometimes irregular) intervals.  The process was not continuous. The oven was filled with ware, fired to temperatures up to 1300ºC, (and sometimes, for specific pottery recipes, up to 1450ºC) cooled and emptied. Then the process would start all over again. Busy potteries aimed to fire their kilns regularly, on a weekly basis, placing, firing and drawing on the same days every week.

What's the difference between a bottle oven and a bottle kiln  

The terms, bottle oven and bottle kiln, are often used to mean the same thing - a complex brick-built, bottle-shaped structure for the firing of pottery or associated materials. But there is a difference between the two.

Within the industry, bottle oven usually meant the potters' oven (for the firing biscuit or glost ware) which had an open flame that passed from the firemouths directly into the firing chamber to envelop its contents.

A bottle kiln was designed and built differently and was usually a muffle kiln. It was constructed in such a way that the products of combustion (flames, gases, smoke, sulphur fumes and dust) were circulated through flues surrounding a sealed firing chamber, rather than entering it. Kilns of this type included enamel and hardening-on kilns, both used in the decorating process.

There were other types of ovens which included two-tier ovens (with an upper and lower chamber) and salt glaze ovens.

There were other types of kilns which included calcining, frit, brick, tile and lime kilns.

Usage of the two terms did vary from factory to factory, so it's complicated and difficult to be precise.

Bottle Oven and Kiln classification

In their heyday, the different types or variants of bottle oven and kiln were not listed or classified, although Ernest Sandeman in his book 'Notes on the Manufacture of Earthenware' 1921, did describe each type.

A simple classification does help to understand how they were built and how they were used.

Bottle ovens and bottle kilns can be classified into four main types. Within these four types are additional variations. There is also a fifth type, but, strictly speaking, it is not a bottle oven but a downdraught beehive brick kiln. It had no bottle-shaped chimney stack but is included here since it was also seen in the landscape of The Potteries.

The twelve variants are identified here.

1.1 - updraught hovel oven
1.2 - updraught stack (or cone) oven
1.3 - updraught hob-mouthed oven
1.4 - updraught skeleton oven

2.1 - downdraught with separate chimney oven
2.2 - downdraught with integral stack, Wilkinson Patent type ("true downdraught") oven
2.3 - downdraught hovel oven

3.1 - decorating (enamel) muffle kiln
3.2 - hardening-on muffle kiln
3.3 - fireclay muffle kiln




The updraught was the simplest and most common type of bottle oven in the heyday of the pottery industry. There were four types of updraught oven.

1.1 Updraught hovel oven

Sometimes known as 'oven and hovel' or in the Potteries dialect, 'ovn n ovvl.'

Bottle oven, updraught hovel oven.
Cross section diagram and external view of an oven at Gladstone Pottery Museum, Longton
Drawing and photo: Terry Woolliscroft Collection

This bottle oven consists of an inner firing chamber, with a domed roof called the crown, in which the pottery ware was placed and fired. Iron bands, called bonts, were secured to the firing chamber to support the structure during firing when it was subject to severe mechanical stress caused by temperature rise and fall.

The firing chamber is enclosed by an bottle shaped structure called the hovel. The hovel acts as a chimney, taking away the products of combustion, creating draught and protecting the inside from the weather and uneven draughts. The hovel also encloses the work space used by placers, oven men, odd men and the fireman. Sometimes the hovel became part of the factory workshops.

Entry to the inside of the firing chamber is through a doorway called the wicket. This doorway is big enough for a placer, with a full saggar balanced on his head, to pass though easily. During firing the wicket is sealed with brickwork and daubed over with clay. It is then known as the clammins.

Firemouths, situated around the outside of the oven at ground level, are connected to brick flues and bags (small chimneys) on the inside of the oven. These carry the intense heat from the coal, burning in the firemouths, to the ware inside. The flues converge at the well hole at centre of the domed floor of the oven.

The intense heat rises up through the setting and then out through the top of the firing chamber and up its chimney stack.

At its peak the oven when firing biscuit pottery would reach temperatures of over 1200ºC.

This updraught hovel oven would have been used for firing both biscuit and glost pottery.

1.2 Updraught stack (or cone) oven

This type of oven has its chimney stack built directly onto the shoulder of the crown of the oven. Sometimes known as 'close coupled'.

Bottle oven, updraught stack (or cone) oven.
Cross section diagram. Drawing: Terry Woolliscroft Collection

The updraught stack oven has no separate hovel. This is the form developed when a series or row of ovens were grouped together in a workshop, the chimney stacks rising through the roof of the building.

These ovens are solid and compact but they tended to be more difficult to repair since the chimney stack rose directly from the crown. (What does the owner do if a fault appears in the structure of the firing chamber?!) They also took longer to cool down.

The updraught skeleton oven looks very similar to the updraught stack oven but it was easier to maintain. See details below.

Bottle oven chimney stacks rising through the roof of the factory
Bottle oven, updraught stack (or cone) oven
Bottle oven chimney stacks rising through the roof of the factory
Sutherland Road, Longton
Photo: unknown source  Date: unknown

1.3 Updraught hob-mouthed oven

This was an older design of firing chamber, largely superseded in the late 19th and early 20th Centuries.  The firemouths of these ovens projected from the firing chamber side walls by up to 2 feet (0.6 metres) to create a hob or shelf.  A square hole constructed in the shelf was used to feed coal down onto the firebed below. The hole was covered, when baiting was not being carried out, by a fireclay slab.

Fireman attending hob-mouth of a bottle oven
Photo: Unknown source Date: probably 1950s

Bottle oven - hob mouthed View of baiting through the top of the hob
Bottle oven, updraught hob mouthed
View of baiting through the top of the hob
Photo: unknown source  Date: unknown

This method of baiting through the top of the hob was regarded as 'old fashioned' but it had the distinct advantage that cold air was prevented from rushing in and being drawn into the oven flues during baiting (unlike a firemouth with opening front doors which did allow cold air to be sucked into the interior of the oven).

Generally, a hob mouthed oven was of the updraught stack oven type. Two good examples, which still stand, (2019)  are in Stoke at the Falcon Pottery, Sturgess Street.

Bottle ovens - hob-mouthed stack type Falcon Pottery, Sturgess Street, Stoke
Bottle ovens, updraught hob-mouthed stack type
Falcon Pottery, Sturgess Street, Stoke
Photo: unknown source  Date: unknown

Hob Mouth on an oven at  Falcon Pottery, Sturgess Street, Stoke
Hob mouth
Falcon Pottery, Sturgess Street, Stoke
Photos: Terry Woolliscroft Collection  Date: May 1976
Photo taken during The Bottle Oven Survey 1976 here>

Baiting the hob mouthed oven
Photos: unknown source  Date: unknown

Baiting hob mouthed oven
Fieldings, Crown Devon Pottery, Stoke
Photo courtesy: The Sphere Magazine Date: 1930

1.4 Updraught skeleton oven

This looks, at first sight, very similar to an updraught stack oven. But it is constructed completely differently. This updraught skeleton oven tended to be preferred by pottery owners since it was easier and less expensive to maintain.

In the updraught stack oven the chimney is built directly onto the shoulder of the crown of the firing chamber. But in an updraught skeleton oven the chimney is built up from ground level, but very close to the firing chamber with just about a one brick-width gap between the two. The firing chamber was therefore completely separate from the chimney and could be easily maintained or knocked down and rebuilt. This simple graphic shows the differences.

This oven variant, just like the updraught stack oven, could be built in a row in a workshop, the chimneys rising through the roof of the building. It has no separate hovel so there is no working area between the hovel and the firing chamber.

This design of oven became very popular in the early 1900s because it seemed to combine all the best qualities of the different types of updraught oven. It was simple in design and construction, relatively simple to operate, easy to build and repair and gave satisfactory results.


This type of bottle oven is a more complex design than the more simple updraught. It was developed in the early 1900s to make more efficient use of the firing fuel (coal).

Technically, the oven should be called "updraught-downdraught" since the hot gasses pass through the setting of saggars not once but twice, theoretically extracting as much heat as possible from the burning coal fires. From the firemouths, the intensely hot gases flow upwards to the crown where they are deflected downwards through the setting of saggars containing pottery, and are then drawn out through the flues in the floor of the oven. The control of the flow of the hot gases was made by the use of dampers (flaps, over the crown, quarter and shoulder holes) which were opened and closed during the firing cycle. It was skilled work and the process was not written down since every oven was different.

Downdraught ovens were used mainly for biscuit firing, as it was considered that they were more economical in fuel, and that they could be worked to produce a more regular heat over all the oven.

There are three variants of downdraught oven.

2.1 Downdraught - with separate chimney

Some downdraught ovens were constructed with a chamber underneath the firing chamber bottom into which the downdraught flues ran. From this chamber a main flue was connected to a tall chimney stack (or shaft) standing separately from the oven. This chimney could be connected and used in common by several downdraught ovens. The main flue to this chimney was fitted with a regulator door that could be opened or closed, at will, to control the draught. The oven itself had its own bottle-shaped stack similar to an updraught oven.

This type of oven was lumped, kindled (lit), and baited in the same way as an updraught oven, but as it came up to a sufficient heat, the damper on the crown hole was closed and the regulator door in the flue to the outside chimney was opened. Heat was thus drawn, by draught, from the firemouths, up through the bags, and up to the oven crown. It was then deflected down through the setting of saggars containing pottery, into the bottom of the oven, into the exit or extract flues, and then away through the chamber to the outside chimney.

The "Clement Robey's Patent Oven" is an example of a downdraught. The patent also included the method for converting an existing updraught oven to a downdraught. 

There was a great deal of interest amongst Staffordshire potters in the 1880s for improving the performance of pottery ovens. Wilkinson and Minton also took out oven improvement patents. More here>  

It was claimed that this new oven design would save 35 to 50% in fuel, would produce a more uniform finished product, and would reduce saggar losses. The flat floor to the oven helped placing. Sampson Bridgwood Ltd. of Longton invested in Robey patent ovens in 1880 but by 1890 described the alterations as a 'failure'.

Advert for Robey's Patent Downdraught Oven
Source: Keates Directory of The Potteries and Newcastle 1879

2.2 Downdraught - with integral stack

These ovens were constructed with separate exit or extract flues below the oven base, rather than with a chamber as described in 2.1, above. This design avoided the expense of a separate outside chimney. These exit flues continued up the inside walls of the oven between the 'bags' eventually connecting to the oven's integral bottle-shaped chimney stack, above the crown. They were sometimes known as a "true downdraught."

After lumping, kindling, and first baiting, when the oven temperature was beginning to rise, hot gases passed from the firemouths, through the bags and up to the crown of the oven. Here the hot gases were deflected and directed downwards through the setting (between the saggars containing pottery) and down through the flues in the oven floor. Hot gases then passed to the flues in the inside walls to escape above the crown and up into the bottle-shaped chimney stack.

Bottle oven, downdraught, integral stack. Wilkinson Type.
The path of the hot gases from the firemouths was controlled by the use of dampers.
Drawing: Terry Woolliscroft Collection

The construction of this type of oven was complex and expensive.

The draught obtained by means of an oven with an integral stack may not have been sufficient, and if several ovens were to be built on the downdraught system it was probably cheaper to build an outside chimney to connect them all. The working results would be correspondingly better. 

Extract from a drawing of a downdraught biscuit bottle oven by Stanley Hind 1927
Bottle oven, downdraught, biscuit, integral stack. Wilkinson Patent
Extract from a drawing by Stanley Hind   Date: 1937
Larger file for download here>

Description in 2.1 and 2.2 above are edited extracts from Chapter 13, Ovens and their Construction, from The Manufacture of Earthenware by Ernest Albert Sandeman, published 1921.

2.3 Downdraught hovel oven

The drawing below shows a downdraught bottle oven, with a separate hovel. The hovel acts as the chimney stack to create a draught while the oven is firing. It also protected the oven itself, and the placers and firemen employed to make it work.


The photographs below are of a unique model of a 'Wilkinson Type' downdraught bottle oven. It was donated to Gladstone Pottery Museum> in 1977 by Howletts, the renowned Potteries bottle oven builders.  The model is built to scale, exactly to the drawing above.

Gladstone Pottery Museum model downdraught bottle oven by Howlett 1977
Gladstone Pottery Museum model
Downdraught bottle oven by Howlett 1977 

The oven has the following specification:
  • 11 x firemouths
  • 1 x crown damper
  • 7 x quarter dampers
  • 11 x updraught flues, situated between bags

Gladstone Pottery Museum model
Downdraught bottle oven by Howlett 1977
Close up of wicket, mouths, bonts

Gladstone Pottery Museum model
Downdraught bottle oven by Howlett 1977
Shows size of the model with viewing panel removed,
showing the crown of the oven.

Gladstone Pottery Museum model
Downdraught bottle oven by Howlett 1977
Shows the top of the crown, with crown damper, quarter dampers, and flues

Gladstone Pottery Museum model
Downdraught bottle oven by Howlett 1977
Looking down into the oven through the crown.
Shows bags, well hole, and unde-floor flues.

Click here> for a ten-frame Gif of the Bottle Oven Model on a turntable


There were three types of potters' muffle kiln: decorating muffle (sometimes known as enamel muffle), hardening-on muffle, and fireclay muffle.

3.1 Decorating (enamel) Muffle Kiln

For the decorating enamel fire. Built in such a way that the flames and harmful gases of combustion were kept away from the pottery ware in the setting.

In this coal-fired kiln the flames did not directly enter the firing chamber as in downdraught and updraught ovens, but were led around the outside of the chamber by a series of flues. In this way the delicate decorated colours of the decorated pottery were protected. The firemouths were kept separate from the kiln chamber.

A muffle kiln was a lot smaller than the other types of bottle oven and temperatures reached were lower at around 850ºC.

This temperature made the decorated colours permanent (without firing, the colours would easily rub or wash off) and did not need the higher temperatures required biscuit and glost.

Muffle kiln, for firing decorated pottery
Cross section and external view of the unique kiln at Gladstone Pottery Museum, Longton
Drawing and photo: Terry Woolliscroft Collection

Inside the muffle kiln chamber at Gladstone Pottery Museum and outside a muffle kiln in Longton
On the left: inside the muffle kiln chamber, on display at Gladstone Pottery Museum 2014
On the right: the exterior of a muffle kiln showing four firemouths.
Market St., Longton.
Photo: unknown source  Date: Unknown

Muffle decorating or enamel kiln
Huge, five-mouthed kiln. Fireman baiting.
Photo: unknown source  Date: unknown 

Bottle oven, muffle kiln, Furnivals, Elder Road, Cobridge, Stoke-on-Trent
Charlie Boardman emptying the ash pit after a firing.
Photo: Courtesy of  Jenny Ward (Thank you Jenny!)  Date: 1930s

Muffle kiln cross section

3.2 Hardening-on muffle kiln

Biscuit ware which has been decorated with an underglaze print or with hand painted pattern sometimes needs to be 'hardened on' so that the decoration won't smudge during the glaze dipping process. The hardening-on fire is at a relatively low temperature of around 700ºC  and ensures that the applied colour is not disturbed during dipping and that the oils in the colour are are evaporated.

The hardening-on muffle kiln was usually smaller than an decorating muffle kiln. Updraught

Bottle oven - muffle hardening-on kiln Oven interior Spode 1900 - 1920
Muffle hardening-on kiln  - interior.
Spode factory, Stoke
Photo: source unknown  Date: 1900 - 1920

Extract from an article about Enamel and Hardening-on Kilns  1927

download pdf here>

3.3 Fireclay muffle kiln

Fireclay products, for use in bathrooms and kitchens, are very large and very heavy! A fireclay bath for instance needed to be hauled around the factory by a team of men with trolleys, ropes and pulleys. These huge pottery products could not, therefore, be fired in a conventional bottle oven using saggars to protect them from the flames and products of combustion of the coal. No saggar was big enough!

Fireclay pottery was fired in a muffle kiln.  Here the product was stacked in a huge box-like chamber which was kept sealed and away from the flames, smoke and other products of combustion of the burning coal.

Muffle oven firemouths Twyfords Stoke fireclay factory 1929  v1
Muffle kiln firemouths
Twyfords, Stoke fireclay factory Date: 1929  

The photos, here>, show the construction of a huge muffle kiln, for firing fireclay sinks, baths and urinals at the Twyfords factory, Shelton New Road, Cliffe Vale, Stoke-on-Trent.


A calcining kiln is not used to fire pottery.  Its purpose is to prepare (make friable through roasting at very high temperature) some of the raw materials, such as flint or bone, used in pottery bodies. During calcination, the materials change their nature making them suitable for crushing and grinding/milling to a fine powder suitable for adding the pottery body.

When they are in their raw state, flint and animal bones are impossible to crush as they are too far to hard. But if they are burnt or calcined they become brittle and can be powdered with ease.

The calcining kilns for flint or bone were similar in construction. There was no particular reason why the chimneys for calcining kilns should be bottle shaped other than to get a good upward draught for the fires below.

Flint occurs naturally as hard, black/grey pebbles within cretaceous chalk beds. When calcined above 1000ºC crystalline water is driven off, shattering the pebbles and leaving them softer, lighter and whiter. This makes them easier to crush and grind. After milling to a fine powder, this flint is added to the pottery body, according to a recipe. Flint is a refractory material used to provide silica in the body. It is also used in glazes. It increases firing temperature and craze resistance but reduces plasticity and shrinkage.

Bone is a component of pottery known as bone china. Calcined animal bone, usually cattle bones, preferably Ox shin bones, are used. About 50% of the bone china body recipe consists of this calcined animal bone. (The remaining 50% being largely made up of China Clay and Cornish Stone.) It is the bone which gives bone china its brilliant whiteness and translucency. Bones are calcined at about 1150ºC to ensure all animal matter and other contaminants are burned away thus rendering the calcium phosphate inert

The process
The calcining kiln could consist of one or two chambers. The hovel built above acted as the chimney to create draught to aid combustion. Filling the calcining kiln was a skilled job. The bowl of the kiln was filled with the flint pebbles or raw bones, layering the fuel with the material to be calcined.

  • Coal was used to calcine flint. About one hundredweight (Approx 50 kgs) of coal was used per ton (1.02 tonnes) of flint. 
  • Bone could be calcined with coal or wood as the fuel, although wood was preferred in order to reduce the possibility of iron in the coal contaminating the batch. Bones which had previously been boiled to remove as much tissue as possible, would be layered with the fuel, as in flint calcination. Because of its organic nature bone required little fuel once combustion had commenced.

The time taken to calcine flint would depend on the type of flint, the quality of the fuel and the climatic conditions, but would take 8 to 16 hours. Bone would be quicker.

The calcined product was allowed to cool before being withdrawn manually through draw holes at the bottom of the firing chamber. Around 10 hours would typically be required for cooling. The whole process would take around 24 hours.

Calcining kiln 
Cross section diagram
Drawing and Photo: Terry Woolliscroft Collection

Calcining kiln
Still standing (2016) in Hanley.
Former Johnson Bros., Trent Works.
Kiln is charged and ready for firing to calcine flint pebbles
Photo:Terry Woolliscroft Collection   Date: July 1975

Calcining kilns Dalehall Mills Ltd., Adkins Street, Cobridge, Stoke-on-Trent photo D. Morris c1975
Calcining kilns
Dalehall Mills Ltd., Adkins Street, Cobridge, Stoke-on-Trent
Photo:  D. Morris   Date: c1975
Courtesy of Staffordshire Past Track here>


Strictly speaking, this is not a bottle oven or bottle kiln since it has no characteristic bottle-shaped chimney stack. But it is included here since it too could be found in the landscape of The Potteries. No more remain.

The kiln had a domed roof and a perforated floor under which ran flues leading to the separate chimney stack. The circular or 'beehive' kiln had a capacity of about 12,000 bricks. Coal was lit and burned fiercely inside the eight firemouths around the outside of the oven. Hot gases were directed upward from mouths through bags (small chimneys inside the kiln itself) and then downwards from the underside of the dome and through the stacked bricks being fired into the under-floor flues, pulled by the draught from the chimney.

Cross section of a beehive type downdraught kiln
Image: source unknown

The firing cycle took around two weeks: two days for setting, three days for the water smoking period to drive off any moisture left in the bricks or tiles, two days for firing to full temperature, one day soak at full heat, then another three or four days to cool down and a further day to draw.

Beehive Brick and Tile kiln
Wheatly & Co Ltd, Trent Vale, Stoke-on-Trent
Photo: source unknown  Date: mid 1950s

Beehive Brick and Tile kiln A worker on top of pottery kiln in the yard  of Wheatly Brick & Tile Co Photo: source unknown  Date: mid 1950s
Beehive Brick and Tile kiln
A worker on top of pottery kiln in the yard
 of Wheatly Brick & Tile Co
Photo: source unknown  Date: mid 1950s

Beehive Brick and Tile kiln  Wheatly & Co Ltd, Trent Vale, Stoke-on-Trent   Baiting the hob mouthed oven with coal
Beehive Brick and Tile kiln
Wheatly & Co Ltd, Trent Vale, Stoke-on-Trent
Baiting the hob-mouthed oven with coal
Photo: Source unknown  Date: mid 1950s

Beehive Brick and Tile kilns  Knutton Tileries Photo: source unknown  Date: 1930s
Beehive Brick and Tile kilns. At least 22 can be seen here
 Knutton Tileries
Photo: source unknown  Date: 1930s

Fireclay Hole and Works, Cobridge, Stoke-on-Trent
Photo: Source unknown  Date: unknown

Tunstall Beehive Kiln at Platts tile works
Photo: unknown source  Date: unknown

Demolition of a Beehive Kiln

Here is an amazing video, on YouTube, of the demolition of a beehive kiln. Watch it to the end. I guarantee you will never forget it.

Description of firing a downdraught beehive kiln by Alan Hopwood, May 2016

The 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.

For definitions of unusual Potteries words go to The Potbank Dictionary here>