As in the case of bricks, open-air drying-places may be either on the ground, or in storeys. The former are only possible for small installations which make mainly flat tiles. They are mere sheds like those used for bricks, but they must, on accountof the shape of the tiles, be fitted with open shelves of suitable dimensions.
So-called mechanical tiles, which are made of soft or semi-firm paste, are received as they come from the press on small frames ("planchettes") (Fig. 406) slightly larger than the tiles. In order not to have several kinds, their dimensions are fixed at: .45 by .25; the laths being .04 to .05 wide and .01 thick; this being so they can be used for any products. To avoid waste they must be well made.
After trimming, the frames with the tiles on them are placed on the shelves of the drying-sheds. In constructing these shelves we must take into consideration the space at disposal and the dimensions of the tiles; they are constructed economically and so as to take up as little room as possible, leaving the space strictly necessary for moving about.
When the drying-places are on the ground-floor, the frames are placed on special barrows with shelves (Fig. 408) to be taken to the drying-shelves; if the tiles are too high to be put on these barrows, platform barrows are used like those serving for bricks (Fig. 407).
Fig. 406. "Planchette" for Tiles.
Fig. 407. Platfom Barrow.
Fig. 408. Shelved Barrow for Tiles.
Fig. 409. Shelved Drying Waggons.
Tiles made of hard clay are firm enough to do without frames. They dry very quickly, hence the empty space in the shelves is much reduced, and more tiles can be placed in less compass. M. Dumont, one of the originators of this kind of manufacture, only leaves about 2 3/4 inches between the shelves. Each shelf is formed of three strips for tiles of 28 to the square metre, and of four for tiles of 13 to the metre. To move the tiles, a two-pronged wooden fork is used, which is slipped under them and afterwards withdrawn.
M. Dumont also used movable drying - places formed of shelves mounted on wheels. When the weather is fine, these may be left in the open air, and desiccation takes place rapidly; in unsuitable weather, they are placed in a drying gallery, which may, with the limitations already mentioned, be usefully employed for the drying of tiles.
Fig. 410. Tile Barrow.
For transporting the products, M. Dumont used a special barrow (Fig. 410), holding twenty large-size tiles on edge, and easily handled among the shelves, thanks to its shape.
Communication between different storeys of the drying-sheds is made by lifts adapted for taking barrows, or by special tile-raisers with swinging trays like that represented in Fig. 187.
Only two systems of drying are possible for regular manufacture: storeyed drying-places, or closed galleries. The cost of their installation has been calculated (p. 182); but to the first estimate must be added the cost of the shelves, and also that of the "planchettes" if soft or semi-firm clay is used.
A building like the one shown in Figs. 176 and 177 is sufficient for a daily production of 20,000 to 25,000 tiles from soft clay. For such an output we must estimate the cost, in addition to that of the building, at -
Planchettes at 10 centimes each.....
With hard clay, the same building would serve for double the daily production mentioned.