Looking over
this link that I posted yesterday does show that certain grades of perlite do have some sort of treatment: dust reduced, water repellent and bitumized/coated being the main treatments. It does not say what these treatments are, so I suppose they might contain urea formaldehyde, but a more intense google search still shows the main use of urea formaldehyde with perlite is as a mix for insulation.
I thought that link might come in handy - certain grades are more appropriate than others, and a few grades shouldn't even be considered.
On a side note, it came to me that adding perlite to Jiffy Rock would probably work just fine - perlite has excellent thermal resistance properties, so no worries about it melting during the baking process, or so I would think; perlite is used as fire resistant insulation among other things...
And as noted by Mr Wilson, I wouldn't use perlite to cast in - trying to get it all off the outside would be a royal pain and if you didn't, it
would shed. I do not see a problem with it coming out of the rock over time, and I do not see much about it shedding being reported in the water garden and freshwater forums, where they have been using perlite for years. I think that isn't really a big issue - I'd still be more concerned about its "filtering capabilities" and how that might cause the rock to hold too much detritus, or the potential for it containing urea formaldehyde, or whether the aluminum content would affect anything. Mr Wilson says he thinks it (aluminum) would be safe over in the 'Reef Ceramics' thread, and no one else has posted info to the contrary, so I might try some if I can find it.
Anyway, those are my thoughts, lol...
