What is Perlite?
Perlite is an amorphous glass found in areas of volcanic activity. Perlite is a volcanic rock, composed mostly of silicon dioxide. It also contains water both as H2O and OH. In its raw form, Perlite resembles pebbles or rocks. However, in order to make expanded Perlite for agriculture, construction and industry use, the raw Perlite must be heated in a furnace to the melting point of glass.
First, Perlite is crushed then sized. The crushed raw pebbles of perlite are then passed through a furnace and heated to approximately 1600F. At that temperature, the amorphous glass begins to melt and the water molecules that are trapped within the perlite rock structure turns into steam and expands. As the steam escapes the melted glass, it creates thousands of micro-channels. In other words, the raw Perlite rocks pop like popcorn. On average, Perlite expands between 3 to 17 times its original size, based on the water content of the particular perlite variety. The expanded Perlite is then ready for use.
The thousands of micro-channels within the Perlite allow it to work like a sponge. These rocks absorb water via capillary action and store it until the environment around them dehydrates. Although perlite is an organic compound, unlike natural sponges, perlite does not undergo decomposition over time. As the environment dries, the wet Perlite slowly releases water back into its surroundings, making the stored water available to the root tips.
Perlite appearance ranges from white to black, including red, brown, green and even blue hues. Apart from horticulture, Perlite is also used in construction as concrete aggregates, plaster, as texturizing agents, as insulation and also as a filtration aid for various fluids. Perlite is safe. It does not harm the soil. Perlite has been used as a soil additive in gardens for over 50 years.