Athletic playing surface with granular material between pile elements

Abstract From the Canadian patent

A playing surface for athletic games, such as tennis comprising, a flat, firm subsurface, a pile fabric disposed on the subsurface comprising a relatively flexible, moisture-impermeable backing and normally generally upstanding pile elements resembling grass a compacted layer, of granular mineral material disposed among the pile elements on the backing to a depth from about 75% to substantially equal to the length of the pile elements, the mineral layer comprising less than 10% clay and further comprising a quantity of moisture retaining material sufficient to maintain the moisture content of the mineral layer above about 3% by weight under normal climatic conditions.