Perlite Vs. Vermiculite Incubations

Perlite and vermiculite are the most common incubations mediums for reptile and bird eggs. Both maintain humidity within an egg container and discourage the growth of fungi. They are light minerals that expand on heating. Perlite is a volcanic glass that contains between 2 and 6 percent of water. When heated to about 1600 degrees Fahrenheit, it expands to between four and 20 times its size. Vermiculite is clay, a silicate mineral that is a weathered form of mica. It swells and shrinks with increasing or decreasing moisture content.

  1. Weight

    • On heating, perlite expands into an ultra-lightweight, white and fluffy substance resembling polystyrene. Expanded perlite particle sizes can be as small as fine dust and may cause breathing problems in some people. Even large granules of perlite break down to dust-sized particles. Vermiculite is heavier than perlite after heating, stays in place in the incubation container and is easier to manage.

    Moisture Retention

    • Vermiculite holds water better than perlite because the clay particles can absorb excess moisture. However, clay particles tend to stick together in clumps and do not release sufficient water into the incubator to maintain humid conditions. Vermiculite darkens slightly with increasing moisture content but not markedly so. Perlite releases water gradually and maintains humid conditions but remains white when both wet and dry. This makes it difficult to recognize if conditions in the egg container are moist enough for successful incubation. Dry perlite can absorb moisture from egg shells causing then to desiccate and collapse from the inside.

    Fungus

    • In their pure form, perlite and vermiculite are sterile mediums that inhibit fungus growth. Some varieties of vermiculite bought from garden centers or pet shops may contain soil. The soil introduces mold and fungus that will rot the bottom of the eggs. Perlite has a neutral pH while vermiculite is more alkaline at between 7.0 and 9.5. This puts vermiculite at a disadvantage as molds and bacteria prefer a more alkaline environment for growth.

    Mixing

    • A favored option among professional and amateur breeders is to use a mixture of perlite and vermiculite as the incubation medium. This balances out each material̵7;s advantages and disadvantages. Vermiculite has a longer history as an incubation medium than perlite so many breeders prefer to use a greater proportion of it in a mixture with perlite. The mixing ratio can be as high as three parts vermiculite to one part perlite, though two to one and one to one vermiculite to perlite mixtures are increasingly popular.