Rockwool
Rockwool is made from Basalt rock and chalk. The rock is heated to the melting point and then blown into fibers that resemble cotton candy as the rock is fluffed to 37 times its original size. Rockwool is commonly used in hydroponic growing because it is completely inert and does not break down. Potting up can be done by putting the orchid, original medium and all into a bigger pot and adding more rockwool. Rockwool is sometimes used as the bottom layer when repotting phrags.
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