When perlite ore is expanded or âpoppedâ by rapid, controlled heating, it expands up to 15 times its original volume and takes on a foam-like lar appearance â essentially clusters of microscopic glass bubbles, creating a porous structure. This sical transformation makes expanded perlite an extremely effective aggregate for use in horticultural growing mixes â or, by itself, as a medium in hydroponic growing and as a rooting medium. Usage 1. Grow seeds and nodes 2. Produce seeding 3. Cultivation in greenhouses 4. Hydroponic Cultivation 5. Turf and landscaping 6. Growing media for indoor and outdoor gardening