gasrocks said:Sounds like Napa Floor Dry absorbs moisture which is the exact opposite of what I need.
Pumice absorbs water (and actually changes color from white to grey when it gets wet). Not a lot, but a measurable amount. That is why it is used in products like Dry Stall. But then perlite absorbs water, too. The exclusion of water is not really the point of the aggregate, though that may be part of its effect (relative to organic soil). The desired effect comes mostly from breaking up the organic soil matrix, providing gaps, and promoting the efficient passage of water through the medium. Pumice and perlite have the advantage of being light and airy; the air pockets in pumice are open but the air pockets in perlite are closed.
Perlite works like pumice but it comes with a really nasty dust and you have to be careful to protect yourself while you handle it.
