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< prev - next > Construction Roofing and flooring clay_tile_manufacture (Printable PDF)
After the tile is pressed and trimmed, it must be thoroughly dried before firing (see Operation
of a tile production unit). Exactly how long this drying takes depends greatly on the moisture
content of the clay, the particle size of the clay composition, the thickness of the tile, and the
prevailing weather conditions of the area. In very hot areas a tile may dry in five days, while
ten days may be required under some conditions. With an output of around 5,000 tiles per
day it is clear a factory must have room for between 25,000 and 50,000 tiles in its drying
racks. Drying racks and pallets are one of the more expensive elements in a tile factory, so
careful planning is called for.
The racks are typically built up to 14ft high to conserve factory space, usually against outside
walls for easy access and exposure to drying breezes. To stack tiles, boards are put across the
aisle, resting on the stringers of the racks. Since the racks will be holding hundreds of tiles
and one or more people handing tiles up, they must be sturdy. Uprights are placed on
approximately 1.5m centre, and one built from 5cmxl0cm lumber (see figure 27). The
stringers are notched and nailed into the uprights and one made from 3cmx6cm lumber. The
aisles are around 1.5rn wide to allow adequate space for loading and unloading of the racks.
Figure 4: Various pallets and tiles.
Wet tiles must be placed directly from the press onto a pallet to maintain their shape (see fig.
4). Some Roman-type tiles can be placed directly on a flat surface after trimming, but all
larger modern tiles must be kept on pallets until firing. The pallets must be sturdy so that
they can be carried without damaging the wet tile. A well-made pallet will last over 10 years
in constant use. By coating the pallet periodically with used engine oil, it can be preserved
from insects. This allows the tile to slide as it shrinks during drying. Special pallets holding
ridge tiles can be stacked upon each other, without racks, to about two meters high (see fig
Tiles can be moved with a wheel cart: the cart holds the tiles on half inch (lcm) diameter
steel rods and is easily handled by one person (see fig. 5).