Chapter Cropping in rockwool and other inert media

Rockwool is a fibrous material produced from a granite-like rock known as diabase, or basalt. During manufacture the minerals are melted at a temperature of around 1600 C and transformed into fibers bonded together with resins. Initially manufactured for the building trade as an insulator, this spongy material has recently become available in cubes or slabs, to which a wetting agent is added to make it water-absorbent for horticultural use. Other inert products that have been used as growing...