Potteries
Bricks tiles and pottery are all made from clay. Clay is made up of fine grains or shales, similar chemically to slate but with a finer structure (technically brick making clay is hydrated silicate of alumina but there are always impurities in the material, notably iron, calcium and magnesium). This material dates back to when the Earth was formed and geological processes have changed the material from a form of rock to what is in effect a powdery material. Clays are also produced by sedimentary deposition and shales are slay which has been subjected to intense pressures often rather similar to slate.
If you get rid of the water in clay you get a hard material that can withstand rain and the like, in Medieval times bricks were made by forming clay and allowing it to dry out under cover for a couple of years, in hot countries sun dried bricks remain in use tody. To make clay really waterproof (to make brick or pottery jugs etc) you have to cook the clay which drives out more water and causes a number of complex chemical changes in the clay. This process is technically called 'vitrification' and the resulting material will not return to clay when wet. Heating the clay in a kiln or oven produces what is known as 'burnt clay', the technology has existed for thousands of years and a brick layer is technically a 'burnt clay artist'.
The kilns used for firing clay are discussed in more detail under 'Lineside Industries - Prototype industrial ancillary structures - Kilns'.
The two main forms of burnt clay which would qualify for a rail connection are potteries and brick & tile manufacturers. By the time the railways arrived pottery manufacture had become semi-industrialised and was a year-round occupation.
Pottery Manufacture
Pottery covers not only pots, plates and jugs but also domestic lavatory pans, basins and sinks, electrical insulators for telephone or power cables and motor car spark plugs, bricks (discussed separately) and tiles for interior walls, floors and for roofing.
Chemical works often used glazed pottery containers for moving corrosive liquids about the place, one common type was the acid egg which were usually fired on-site. The device was in effect a non mechanical pump, the acid was poured into the container then pushed out down a delivery pipe using compressed air. There were also large egg shaped pottery 'acid jars' used to move acids about from place to place (illustrated in the section 'Lineside Industries - Chemicals and Plastics').
Pottery is basically clay which is then cooked in a kiln to form a rigid material that does not soften when immersed in water.
Basic clay pottery, called biscuit ware, has a rough surface, to make this smooth a glaze is added. The glazing consists of a thin layer of glass deposited on the material by vaporising glass producing minerals in the kiln. Some time in the seventeenth century potters in Germany discovered they could add a waterproof glaze to pottery just by adding salt to the kiln in which the pots were fired. Potters in Staffordshire adopted the technique and this laid the foundation of Staffordshire as the main centre of production in the UK. Other glazes are applied as a liquid and cooked onto the surface in a second firing at a lower temperature than the initial 'biscuit' firing. One common glazing material was galena (Lead Sulphate, the ore from which lead is obtained).
Wedgewood is the most famous firm in the industry, largely because the founder was the first to reproduce 'porcelain' using 'China clay'. Porcelain is also known as 'China ware' as the secret for making it had originally been discovered by the Chinese about a thousand years before, China clay gets its name from its use in making porcelain.
To make earthenware several ingredients are required, non of which are found in Staffordshire. China clay and Cornish stone come from Cornwall, stuff called 'ball clay' comes from Devon and Dorset whilst flint pebbles can be found in Kent. Cornish stone contains feldspar, which lowers the temperature at which the clay will harden. Feldspar is potassium aluminosilicate, the most common form has a little sodium in it as well. Ball clay has good plasticity, strong bonding power, high refractoriness (heat resistance) and fires to a white or cream colour. Most of these raw materials traveled by water, round the coast then via the canals to the pottery towns. Earthenware and pottery all regularly traveled by canal, where the smooth transit saved on breakages, and Staffordshire was soon the principal hub of the British canal system.
The China clay is too stiff to be used alone so it is mixed with the ball clay, however the resulting mix would tend to crack as it cooled and shrank so a powder made by heating and then grinding flint is added. All the ingredients are mixed with water to produce a slurry called 'slip', this is either squirted into moulds or partially dried and squeezed into moulds to make the wares.
After drying for a time the wares are taken to the kilns, the first firing is called the biscuit firing and the rough pottery that emerges is called biscuit ware. The glaze is then added and a second firing at a lower temperature fuses this to the surface.
Electrical insulators are made using China clay, ball clay, feldspar and pure sand, the sand improving the electrical resistance of the material.
Stoneware is waterproof and opaque, it is partly vitrified, that is heated to a high temperature to form something like glass and has a smooth shiny finish. Prior to mechanised glass bottle production the stoneware jar was popular for beer and soft drinks. These jars have one advantage over glass in that the upper section can be left un-glazed, permitting the liquid inside to evaporate from the surface and hence cooling the contents. After about the 1850's most beer, wine and spirits was shipped in bottles but the 'stoneware' jars proved popular for a wide range of other liquids such as inks. By the 1850's machines were being used to form stoneware items, one common application was field drains (about a foot in diameter with a raised ring at one end to fit over the next section. Up to the 1950's soft drinks notably ginger beer were often sold in screw-topped light brown earthenware bottles (commonly called 'jugs') which had been mechanically formed. These generally held about a gallon (four litres) of liquid and there was a deposit on each one. Smaller earthenware bottles of a similar design were regularly used for lunch boxes, often filled with beer.
Terra Cotta is unglazed, usually brownish red earthenware
'The Potteries' in the north of Staffordshire were the centre of British pottery manufacture, extending over an area of only nine miles by three in the upper Trent basin encompassing the old towns of Burslem, Hanley, Longton, Stoke-on-Trent, Tunstall and Fenton (all except the latter being the 'Five Towns' of the Arnold Bennet novels). In 1910 these towns were amalgamated to form a single municipal borough under the name of Stoke-on-Trent which became a city in 1925. Newcastle-under-Lyme although not associated with pottery manufacture may be regarded as a part of the district. Wedgewood's new works of 1769 at a place he named Etruria used steam power to drive the flint, clay and colour mills and this firm probably more than any other transformed pottery from a craft into an industry. The local coarse clay and locally mined coal formed the basis of the industry but all the other materials were brought in by rail, notably the quantities of China clay from Cornwall. Up to the 1980s at least Staffordshire remained one of the worlds principal pottery producing centres, however in 2009 an American firm bought out the last major firms in the area and shifted the bulk of production of Royal Doulton and Wedgewood to Indonesia.
Men working in the potteries and chemical trades, along with woman and all children under the age of 18 in all industries were the only ones who's working hours were determined by law.
The distinctive urban industrial quality of the area has its attractions, however making the huge brick 'bottle kilns' for layouts depicting the era before the BR corporate blue livery appeared represents something of a challenge. Bottle kilns (see also Industrial buildings and ancillary structures - Kilns) were used all over the country, according to a postcard in a friends collection there was at least one as far south as Honiton (in Essex, near the south coast). The illustration below left, based on a photograph taken in the 1930s, shows a typical pottery, points to note are the scale of the kilns (compare with the figures on the pavement) and the heavy stone posts by the entrance to protect the brickwork. Fortunately you can compress things rather a lot and retain the general atmosphere. The version on the right has the kilns reduced by a third, the surrounding buildings are reduced in height slightly to compensate, and the result is a much more compact scene.
Fig ___ Typical small pottery
The illustration shows the two common types of 'bottle kiln', the cone shaped type to the left is the older design, the more bottle shaped example on the right is more recent. Some of the cones were rather tall and slender, the example shown is about average. These old kilns gradually disappeared from the landscape from the 1930's on as the potteries changed from coal to gas and electric firing in the 1920's and 30's (thanks to cheap gas supplies from the Shelton Iron Steel and Coal Co works situated between Etruria and Hanley). Only about a third of the kilns were coal fired by the end of World War Two but these old kilns were not taken down at the time and dominated the landscape well into the post world war two ere. They were finally demolished in large numbers from the 1960's on and by the 1970's there were only a few preserved examples left. The last firing of a bottle kiln was a specially arranged one-off (for one thing it contravened the clean air act) done at a preserved kiln in Staffordshire in 1982, this was filmed for posterity.
An early type of kiln used for pottery and brick making was the 'bottle kiln', early versions of which were often not very bottle shaped but more like a slender cone. One problem in modelling the more curvaceous bottle kilns is their sheer size, although modelled to scale they would probably look too big to anyone who had not actually stood next to one. Bottle kilns were not all the same size however and on the same site there might be two close together one only two thirds the height of the other (see Fig ___).
Making a curved type bottle kiln is difficult, I remember an article by Alan Downes in the model press which mentioned that he had managed to get a potter to run one up for his layout. I enquired locally and would suggest a potter would probably charge between thirty and fifty pounds to model a couple of kilns in N scale. Another option is to have them turned up out of wood and a third option is to find a plastic bottle with a suitable shape but all of these leave you with the unenviable task of adding the brickwork. The bottle kilns I made many years ago for a small pottery on an N Gauge layout were plastic 'party poppers' coated in Milliput.
If you cannot find a potter, wood turner or suitable bottle all is not lost, you can make the thing out of cardboard. Cut a full-size silhouette from a stack of perhaps five postcards, the top one or two centimetres should be omitted. Each of the resulting shapes would then be folded in half and all the folded edges would be glued together. This forms a set of vertical 'ribs' to which you add a short length of card formed into a tube to the top.
Cover the lower ribbed part with tissue paper soaked in glue to give you the basic shape then coat the whole thing with Peco modelling clay, Milliput or fire cement and smooth to shape.
When dry either cover with brick paper strips or scribe in the brickwork. To scribe the horizontal course lines hold the knife on a block of wood and rotate the model against it, then use the tip of the knife to add the verticals. To make life easier you can build a simple straight-sided cone shaped kiln, the drawing below right is of a kiln at Longport alongside the Trent & Mersey Canal.
The associated buildings could be from any source, the Bilt-eeze card kit of a 'Stone Smithy' would do for example, I used two of these for my small pottery.
Fig ___ Bottle kilns
The visible 'bottle kiln' is in fact an outer shell, the kiln itself was a similarly shaped structure built inside with perhaps four foot clearance between the two shells. The entrance was about seven foot high by five foot wide, coal went in in wheel barrows and the pottery went in in large fire clay trays or basins (perhaps three foot by two foot by a foot or so high) called 'saggars'. The saggars were lined with some crushed flint to prevent the pots sticking to them, once filled they were stacked up inside the kiln and the fires were lit. Even with the flint dust lining the new pots tended to stick to the bottom of the saggars and there was an actual job title of 'saggar makers bottom knocker'. This chap was employed to hit the bottom of each saggar as it was lifted out of the kiln. He used a wooden implement to break away the plates, cups or jugs inside, some skill being required to do this without breaking the saggar or the new pots themselves.
For a model layout we can assume that the front of the pottery is at the far side, all we need are some buildings facing into the yard and a kiln or two. The example shown is about as small as you can go, although using a bottle shaped kiln rather than the cone type would reduce the footprint somewhat. The associated buildings often blended into the kiln wall, however that makes modelling rather more difficult and some were free standing as shown. Do bear in mind that your hand has to get into the yard to deal with couplings and the like. The company name might appear in the brickwork on the upper part of the right hand end of the building.
Fig ___ Example model pottery
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