CHAMBERS'S INFORMATION FOR THE PEOPLE. 



Fig. 7. 



outline is required, the profile-mould is used. The 

 thickness of the material is represented by the 

 white space between the outlines b and cc, fig. 7. 



When the ware is ready for the kiln, the articles 

 are placed in baked fire-clay vessels called seggars 

 or sags. These vessels are made of inferior clay, 

 by the workmen during the intervals of their work, 

 and are from six to eight inches deep, and from 

 twelve to eighteen in diameter. The sags are 

 packed full of the dry ware, and are then piled 

 above each other in the kiln, the bottom of one 

 sag forming the cover of another. These rude 

 earthenware boxes are necessary, to prevent the 

 ware from being suddenly and unequally heated, 

 and also to protect it from the smoke and dust 

 of the kiln. 



Fig. 7 represents one method of packing articles 

 in the sags, aa is a section of a sag, 

 provided with projections on which 

 the article, bb, is suspended. In the 

 inside of this, a second article may 

 be placed, as the jug, c, shewn by the 

 dotted lines. A second sag, as dd, 

 is placed above the first, the bottom 

 forming the cover or top to aa. In packing flat 

 articles, as plates, little pieces of clay, of various 

 shapes, as shewn at a, b, c, fig. 8, and 

 known as cock-spurs, stilts, &c. are 

 placed between the articles, as shewn 

 at d y fig. 8 ; this keeps each article 

 separate. 



The body of a pottery-kiln is gener- 

 ally of a conical shape, covering and 

 protecting from the weather the fire- 

 kiln, which is circular, and provided with a domed 

 top, as aa, fig. 9. The furnaces, six or eight in 

 number, are placed equi- 

 distantly round the kiln, as 



b, b. The smoke escapes 

 through th apertures 

 made in the dome. The 

 door for obtaining access 

 to the interior is shewn at 



c. When the kiln is filled 

 with the sags, it is built 

 up, and fire applied to the 

 furnaces. The heat is 

 increased gradually, from 

 the time the fire is put 

 on, till the ware is found 

 to be properly burned. 

 To ascertain this, the 

 workman draws from the 

 kiln what is called a watch, 

 and if this is found to 

 resemble in colour a previ- 

 ously burned vessel, he 



Fig. 8. 



Fig. 9. 



allows the kiln to burn a little longer, and then 

 opens the doors of the furnaces carefully, so as to 

 lower the heat by slow degrees. The burning, or 

 baking, as it is called, usually lasts from forty to 

 forty-two hours, after which the kiln is allowed to 

 cool very slowly. When the ware is taken out of 

 the sags, a child makes the pieces ring with the 

 handle of a brush, used for dusting them, to test 

 their soundness, and then immerses them in the 

 glazing material. The glaze is kept in a large tub, 

 into which the articles are put by the child, and 

 lifted out by a man, who shakes them in the air, 

 and places them on a board, to be conveyed to the 

 glazing-kiln. 



358 



' Three kinds of glazes,' according to Dr Ure, 

 ' are used in Staffordshire one for the common 

 pipe-clay or cream-coloured ware ; another for the 

 finer pipe-clay ware, to receive impressions, called 

 printing body; a third for the ware which is to 

 be ornamented by painting with the pencil. The 

 glaze of the first, or common ware is composed 

 of 53 parts of white-lead, 16 of Cornish stone, 36 

 of ground flints, and 4 of flint-glass : of the second, 

 26 parts of white felspar, fretted with 6 parts of 

 soda, 2 of nitre, and I of borax ; to 20 pounds of 

 this fret, 26 parts of felspar, 20 of white-lead, 6 

 of ground flints, 4 of chalk, I of the oxide of tin, 

 and a small quantity of the oxide of cobalt, to 

 take off the brown cast, and give a faint azure 

 tint, are added. As to the ware which is to be 

 painted, it is covered with a glaze composed of 

 13 parts of the printing colour fret, to which are 

 added 50 parts of red-lead or litharge, 40 of white- 

 lead, and 12 of flint; the whole having been 

 ground together.' 



The above compositions make a very clear, 

 hard glaze, which is not affected by vegetable 

 acids, and preserves its lustre for an indefinite 

 time. When covered with the glaze, the vessels 

 are put into sags, which have been previously 

 glazed with a composition of 13 parts common 

 salt and 30 parts potash. They are then put into 

 the glazing-kiln, which is usually smaller than the 

 biscuit-kiln, the sags being piled in the same 

 manner as at the first burning. The heat of the 

 glazing-kiln is very low at first, but gradually 

 increases until it reaches the melting-point, when 

 great care is necessary to prevent the temperature 

 from suddenly falling. To ascertain when the 

 temperature is high enough, balls of red clay, 

 coated with fusible lead-enamel, are employed. 

 When these balls become of a slightly dark-red 

 colour, the temperature is sufficient to glaze 

 ordinary pipe-clay ware. The fire is kept on for 

 about fourteen hours, after which very little fuel 

 is added, and the kiln is gradually allowed to 

 cool. The vessels are again tried by being 

 slightly struck by a small wooden hammer, when, 

 if they ring freely, they are sound. 



The colouring of pottery is performed either by 

 what may be called painting, or by printing. The 

 colours used in producing the dipt or sponged 

 ware are of a very cheap kind, as it is only 

 employed for common purposes. In dipt ware, 

 the colours are dropped on before the ware is 

 burned ; and in sponged ware, when it is in the 

 biscuit state. A black dip is made from man- 

 ganese, ironstone, and clay-slip ; a drab, by nickel 

 and slip ; a blue, by cobalt and slip ; a yellow, by 

 yellow clay alone, or by a compound of red and 

 white clay ; and a red, by a natural red or brown 

 clay, which will burn red. 



The colours used for painting and printing on 

 ware are similar to one another, excepting that 

 the colours for printing are more carefully pre- 

 pared ; both, however, form an important and 

 extensive part of the materials of a pottery. 

 The manufacturers of earthenware are much 

 occupied with the improvement of the variety 

 and beauty of the colours, as well as of the 

 patterns or styles that are produced, and hence 

 a great emulation exists among those employed 

 in the trade. The blue colour in printing 

 is produced from cobalt, which is used with 

 flint, ground glass, pearl-ash, white-lead, barytes, 



