Perlite - 1 litre
Perlite is made by rapidly heating volcanic glass (obsidian) at high temperature, which expands it many times its original volume into light, porous white granules. That porous structure lets perlite hold water on its surface while keeping air inside its core, which is why it's a widely used addition when preparing substrate for mushroom growing.
In practice, perlite is rarely used on its own; it's usually mixed with other grow supplies. A common base mix is coco coir, vermiculite and gypsum, where perlite can be added for extra aeration or used to partly replace vermiculite, depending on the moisture balance you're after. Perlite is also used as a loose, moist layer at the bottom of a grow tub, to keep humidity stable through evaporation during the grow.
Perlite versus vermiculite
Perlite and vermiculite are often mentioned together, but they don't play the same role. Vermiculite holds significantly more water and mainly regulates moisture, while perlite is mainly there for aeration and drainage and absorbs less moisture itself. Many growers combine both: vermiculite as a moisture buffer, perlite to stop the substrate from becoming too dense and low on oxygen.
Usage
Rinse perlite briefly before use to remove stone dust, and let it drain before mixing it into your substrate or spreading it in a grow tub. When using it as a moist layer, mix it with water until it feels damp but no longer releases water when squeezed, and refresh the water regularly to prevent mould.
Storage
Dry perlite is an inert mineral and keeps practically indefinitely in a sealed pack, stored in a dry place. Once moistened, it's best used within a few days to avoid bacterial growth.
Check out our other mushroom-growing supplies at Dutch-Smart, such as microfilter bags.
