Tiles - How are they fired?

Writing up some tiles ATM - quick question to any potters, are they fired flat? and are they wasteful in the kiln? How much space needs to be left over them?

Many Thanks

Alex

Answered my own question:

http://lakesidepottery.com/HTML%20Text/Tips/Making%20Ceramic%20Tiles.htm


Firing Tiles
For bisque firing, you can stack tiles on top of each other, or put them into a tile setter.

For glaze firing at low temperatures, tiles can be put into many types of tile setters. But if you are using high fire clay and firing it to maturity, the tiles will slump at high temperatures. In these cases you have to fire the tiles on a flat surface.

Fire tiles on a kiln shelf dusted with silica sand.

Make a moat around your tiles by putting bars of clay around their edges. This helps them heat from above and below rather than the edges heating faster.

Remember that clay will shrink, and you have to adjust for this when making your tiles. To determine shrinkage, take a slab of clay and incise a line 100 millimeters long. Re-measure this line at the bisque and high fire state. If the line ends up 90 mm's long then your shrinkage rate is 10%. If your ending number is 87mm's then your shrinkage rate is 13%, etc. Remember to make the first line at the same dryness stage as you will be cutting your tiles, as there will be shrinkage between wet and leather hard as well.