Articles
NEW DEVELOPMENTS IN THE USES OF GRADED HORTICULTURAL PERLITE
Much industrial perlite is quite unsuitable for horticultural purposes; thus it is important to ensure that ‘horticultural perlite’ has been prepared from ‘crude ore’ free from any source of contamination, and that the finer particles have been removed.
Particle size is an important factor in the effectiveness of perlite in its various horticultural uses and the availability now of four distinct size grades should, it is hoped, enable more precise research to be undertaken on the optimal use of the material.
Expanded perlite is an important industrial product used worldwide for its very high thermal and acoustic insulation properties.
It may be mixed with a variety of materials to produce plasters, roof insulation or the high temperature insulation of furnaces.
Equally it has cryogenic applications at temperatures approaching absolute zero.
It is an invaluable filter-aid for liquid filtration of materials ranging from beers and wines to swimming pools.
It is used as a filler in plastics, paints and cleansers and as a carrier for many pharmaceuticals.
Its horticultural uses provide only a very small outlet for the perlite producers.
Even in the USA, where it has been well established in the plant nursery trade for over 20 years and where the production and processing of perlite ore is the highest in the world, the horticultural market provides only from 8% to 10% of the total consumption.
In most of Europe and in the other Continents this percentage figure is very much smaller.
Not every producer, therefore, is prepared to cater for any specific horticultural needs.
Industrial perlite contains a wide range of particle sizes including a high proportion of very fine dust and for many purposes the presence of this dust is of little or no consequence; for horticultural applications, however, it can be disasterous.
Material around the 250 micron size will promote waterlogging.
The term "fines" is used rather empirically in the industry to designate material up to about 1 mm diameter; for most growth situations particle sizes above 1 mm are required.
Horticultural