608 POTTERY 



it is made to traverse horizontally, in order to vary the speed of the lathe at pleasure. 

 When the belt is at the base of the driving-cone, it works near the vertex of the 

 driven one, so as to give a maximum velocity to the lathe, and vice versa. 



During the throwing of any article, a separate mechanism is conducted by a boy, 

 which makes the strap move parallel to itself along these conical drums, and nicely 

 regulates the speed of the lathe. When the strap runs at the middle of the cones, the 

 velocity of each shaft is equal. By this elegant contrivance of parallel cones reversed, 

 the velocity rises gradually to its maximum, and returns to its minimum or slower 

 motion when the workman is about to finish the article thrown. The strap is then 

 transferred to a pair of loose pulleys, and the lathe stops. . The vessel is now cut off 

 at the base with a small wire ; is dried, turned on a power-lathe, and polished as 

 above described. 



The same degree of dryness which admits of the clay being turned on the lathe, also 

 suits for fixing on the handles and other appendages to the vessels. The parts to be 

 attached being previously prepared, are joined to the circular work by means of a 

 thin paste, which the workmen call slip, and the seams are then smoothed off with 

 a wet sponge. They are now taken to a stove-room heated to 80 or 90 F., and 

 fitted up with a great many shelves. When they are fully dried, they are smoothed 

 over with a small bundle of hemp, if the articles be fine, and are then ready for the 

 kiln, which is to convert the tender, clay into the hard biscuit. 



At a certain stage of the drying, called the green state, the ware possesses a greater 

 tenacity than at any other, till it is baked. It is then taken to another lathe, called 

 the turning lathe, whore it is attached by a little moisture to the vertical face of a 

 wooden chuck, and turned nicely into its proper shape with a very sharp tool, which 

 also smooths it. After this it is slightly burnished with a smooth steel surface. 

 A great variety of pottery wares, however, cannot be fashioned on the lathe, as they 

 are not of a .circular form. These are made by two different matters, the one called 

 press-work, and the other casting. The press-work is done in moulds made of Paris 

 plaster, the one half of the pattern being formed in the one side of the mould, and the 

 other half in the other side : these moulding-pieces fit accurately together. All vessels 

 of an oval form, and such as have flat sides, are made in this way. Handles of tea- 

 pots, and fluted solid rods of various shapes, are formed by pressure also ; viz. by 

 squeezing the dough contained in a pump-barrel through different-shaped orifices at its 

 bottom, by working a screw applied to the piston-rod. The worm-shaped dough, as it 

 issues, is cut to proper lengths, and bent into the desired form. Tubes may be also 

 made on the same pressure principle, only a tubular opening must be provided in the 

 bottom-plate of the clay-forcing pump. The temperature of the various rooms in a 

 pottery is as follows : 



Plate-makers' hothouse 108 Fahr. 



Dish-makers' hothouse 106 



Printers' shop 90 



Throwers' hothouse . 98 



The branches against which the temperature of the hothouse is placed require that 

 heat for drying their work and getting it off their moulds. The outer shops in which 

 they work may be from five to ten degrees less. 



The other method of fashioning earthenware articles is called casting, and is, perhaps, 

 the most elegant for such as have an irregular shape. This operation consists in pour- 

 ing the clay, in the state of pap or slip, into plaster-moulds, which are kept in a 

 desiccated state. These moulds, as well as the pressure ones, are made in halves, which 

 nicely correspond together. The slip is poured in till the cavity is quite full, and is 

 left in the mould for a certain time, more or less, according to the intended thickness of 

 the vessel. The absorbent power of the plaster soon abstracts the water, and makes the 

 coat of clay in contact with it quite doughy and stiff, so that the part still liquid being 

 poured out, a hollow shape remains, which when removed from the mould constitutes 

 the half of the vessel, bearing externally the exact impress of the mould. The thickness 

 of tho clay varies with the time that the paste has stood upon the plaster. These 

 cast articles are dried to the green state, like the preceding, and then joined accurately 

 with slip. Imitations of flowers and foliage are elegantly executed in this way. This 

 operation, which is called furnishing, requires very delicate and dexterous manipula- 

 tion. 



The saggers for the unglazed coloured ware should be covered inside with a 

 glaze composed of 12 parts of common salt and 30 of potash, or 6 parts of potash and 

 14 of salt ; which may be mixed with a little of the common enamel for the glazed 

 pottery saggers. The bottom of each sagger has some bits of flinte sprinkled upon it, 

 which become so adherent after the first firing as to form a multitude of little promi- 

 nences for Betting the ware upon, when this does not consist of plates. It is the duty 



