Tuesday 2 June 2015

Middleport pottery

Today we visited Middleport pottery to do the factory tour and found it a very worthwhile visit.The pottery was without doubt saved by The Prince’s Trust and is the only one in the UK and probably Europe still making and decorating pottery in this way. If you visit by boat there is room to moor with rings by their car park.

Our tour started in the visitors centre where there is a fabulous china model of the work as it would have been in its heyday with its 7 bottle kilns and boiler chimney.DSCN1384

When the factory was built it was know as a model factory as it was specifically designed for efficiency. The materials entered entered at the extreme right of the building and worked their way round in a sort on U being made to slurry then back along the right hand side as they were made into green items, biscuit fired in the first three kilns, then further round to the left being decorated and glazed before being refired in the row of four kilns and finally being packed on the left hand side before being shipped out. The canal side location was essential to all this as that is where the raw materials came on to the site, coal for the boiler and the kilns, clay for the pots. The finished articles also left by the same means form the left hand end by the canal all by Narrowboat.DSCN1386

Today there is just the one bottle kiln, the furthest one behind the boiler chimney. The boiler is still in situé but has not been used since they ran out of coal during the miners strike, so the condition of the boiler is unknown. There is another square tower just to the left of the three kilns. This contained a continuous chain lift running over a wheel at the top and one at the bottom. Shelves of green pots were hung on this at the bottom and they would go to the top and then down the other side. The tower was heated with steam pipes and by the time the pots had done a cycle up and down they would be dry. It is thought that this is the only one in existence.

Once we were into the factory we started right at the beginning with the original motive power for the factory, a single cylinder steam engine with a 15 ton fly wheel,DSCN1389 This had a direct drive through the wall to gears in the next room as well as driving two overhead belt systems. The engine looks in poor shape but its been well greased and they have the money to restore it in the next 12 months when they will install a small gas boiler to fire it. The original Slip pumps today are powered buy an electric motor driving the overhead lay shaft  where the slip(liquid clay) is mixed and

pumped up to the area where they fill the moulds for things like tea pots and mugs.

The slip was also reduced to solid clay for making things like plates and items turned on the wheel. To do this they filled muslin bags and then pressed it between castDSCN1393 iron plates to remove the excess water, before knocking the clay to remove all air bubbles and make it pliable to work. This press was manually powered by the screw handles on the end, today the cay is bought in ready for throwing.

The moulds are made from Plaster of Paris and are only good for about 60 pots so have to be constantly renewed. This is done from a positive model of the finishedDSCN1394 item that is about 20% bigger than full size as the clay shrinks whist it dries in the mould. Some of the positive date back to the first days of the pottery.

The moulds which are in two or more parts depending on the complexity of the design are filed with the liquid slip clay and left to stand for between 20 minutes and an hour depending on the thickness of clay required.DSCN1399 The water is drawn out of the liquid clay by the plaster mould so that a skin of clay forms inside the mould, after the required thickness has been obtained the moulds are inverted and the surplus slip pored out. This returns downstairs to the mixing pit to go round the system another time.

The moulds are left to stand for a while before being opened to remove the very soft damp clay item, The are still very malleable at this stage and have to be treated with DSCN1396care. These are teapots being made in one piece, some items are made in several pieces and put together afterwards like handles and spouts. Once taken from theDSCN1397 mould they are allowed to dry further before someone removes all the joint marks left where the mould parts join together. This is done with a very sharp knife and a selection of wet sponges.DSCN1400 Some of the items they make are pierced, again this is all done by hand using small hand held cutters and the patterns are cut out by eye so no two will be absolutely identical, they may look it but there will be minor differences .DSCN1402 The pieces are now dried further to reduce the moister content before being fired in a gas Kiln. These were introduced with the clean air act when the old coal fired bottle kilns were pulled down.DSCN1387 The only reason one was left standing was because it was built into the other buildings and demolishing it would have resulted it those buildings being demolished at the same time. The bottle kilns had metal bands round them to stop them falling apart with the constant hot cold cycles. These bands are flat iron and they are not continuous but in sections joined by an iron ring to allow them to stretch as the brick work expanded.DSCN1410 The gas kilns were much more efficient allowing a batch to be fired every day where as the old kilns took a couple of days to pack, 3 days to fire and then another couple to unload. Where as men use to climb inside the kilns to load and empty now its put on trolleys and pushed into the tunnel kiln through the end door.DSCN1423 After the pots are fired they are then decorated. This is done using transfers. The transfers are printed on tissue paper and have to be printed just before they are attached to the pots. The printing is done by an engraved copper roller and as the paper comes off the printer it is hung on long endless linen lines and slowly works itsDSCN1412 way down the line of decorators. Each decorator takes a sheet of transfers and then cuts them up and wraps the item in them without a crease or overlap. They only get one shot at it because once its on the the biscuit fired clay there is no going back. The work it on using a selection of brushes before it goes to an industrial “dish washer” which dissolves and removes all the tissue paper.

From here the pots go on to be dipped in glaze, again a very skilled job, just like all of them in the factory. To dip the plates and saucers the glazer wears a wire hook onDSCN1416 his thumb so that he can hold the edge of the plate wit two fingers and the hook and rotate the plate in and out of the glaze before racking them up to pass through a dryer.DSCN1417 .

At the other end of the dryer they are stacked in special racks with porcelain pegs ready to go into the kiln for their second and final firing.DSCN1418 Some items actually have three firings, these are items that have the pattern put on top of the glaze. This method used lithograph printed designs which can be multi coloured. The pots have been glazed but are all white, The pattern is then slid off transfer on top of the glaze, again it has to be done with no wrinkles, tears or overlaps. One dry this is fired for the third time. The light green/yellow colour is only the backing and this disappears with the firing.DSCN1420

In addition to this the plates and saucers are mage from the knocked up solid clay, for round items this is done on a wheel on top of a former, bringing a second former DSCN1403down on top to spread the clay to just the right thickness. You can see the green plates behind him in the dryer.

The clay for making these comes in a big role like a sausage and roundels are cut off with a cheese wire. DSCN1405 After firing every item is checked to ensure it is perfect and those that are not are sold as seconds. There are very few total rejects as each item is checked at each stage of production and removed then if need be very small flaws can sometimes be repaired like minor blemishes to the glazeDSCN1419 The visit lasted an hour and a half and afterwards you can see why the pieces cost so much, I would guess there is probably over two man hours in each piece from start to finish. They have just had a new copper roller engraved to print the transfers, there was over a years work just engraving it.

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