Installed Perlite around my first liner install. It found a hole and leaked out. Recovered it, and poured it in my second install. It took a month, but it too found a hole in my block off, and is now on my floor. No mas. Looking at some thermix, but can't find it locally. Shipping is in the $45/bag range, so I'd REALLY like to get it locally. None of the hearth places carry it. Anywhere else I could look? I found some vermiculite that I may be able to mix with cement, but the vermiculite is horticultural, so I'm not sure it's appropriate...