Eugene wrote: >>I once sifted (outdoors!) about a quart (liter) of dry perlite through 1/8 inch (about 3 mm) mesh and found that the fine material made up about 1/3 to 1/2 of the total volume. It may be that this fine material is retaining most of the water and causing problems. I think that's probably the problem I've been having. I don't have the time or patience to sift the perlite I get from the garden center, and also don't want the exposure to perlite dust that would cause. I've found a local source for pumice, in the form of a product called "Dry Stall." It's used for horse bedding, but is a uniform size, is free of fines, and doesn't cost much in the volumes I use. So I think that's what I'll try next. I'll sift a small amount of perlite and re-run my water absorption test with it. I understand the very valid point that it's porosity that matters most, but I still think the absorption information is a useful data point. Mike