I thought I'd share some info about the perlite humidity tek. First off, a friend of mine in Arizona (where it is very dry), has used this technique and swears by it. She used every kind of humidifier known to man and also the handspraying technique.
The perlite tek, when done properly, keeps humidity levels between 95% and 100% EVEN in places where there is almost no humidity in the air. Also, since the humidity is caused by evaporation, the moisture is not in 'droplet' form as it is with handspraying and humidifiers and is less prone to condense out quickly (which causes big variations in humidity).
She says that "Hands down" perlite is best. BUT there are a few things people need to be careful about. She has watched the newsgroups and wrote to me that she thinks that most problems that people have is with one of the following errors (which she also admits to making during her trials).
1) Don't use too much water. Use a 1.5 - 2 inch layer of perlite and no more than 1/4 to 1/2 inch of water. People seem to make the mistake of adding too much water which doesn't leave enough exposed perlite surface area.
2) Make sure that your terrarium doesn't have any hole to drain CO2 . Fanning the terrarium with the top every couple of days is fine.
3) Make sure that the top of the terrarium is a good fit. See the PF website for good directions on a top that will sit well on any terrarium
4) Don't let the cakes sit directly on the perlite all of the time. If you do this the mushrooms tend to get waterlogged. Her recommendation keep them on jar tops or something BUT, after a strong flush, after the fruits have been picked, put the cakes directly on the perlite until the cake starts pinning (about 3-7 days) then put the cake back on the jar tops or whatever.
5) Don't try to squeeze too many cakes into one terrarium. Again, the more exposed surface area the better.
6) Only add water when the level goes below a quarter inch.
