I was a firm believer in using play sand. But, I went a head and tried the shelf liner switch...hey, you can always go to walmart and buy another bag of sand for $3...
Well one day i was at target and i saw a shelf liner there that looked pretty cool....it actually looks and feels like cork but is in fact some synthetic material like plastic. Down sides of the shelf liner i use is that it's the sticky kind, so it can't be removed. And it costs a lot more than the plain white or tan non stick kind.
So, if you switch to shelf liner from sand...the first thing you will notice is that shelf liner absorbs absolutly NO SMELL. It is quite a pain to clean too. BUT, you don't have to worry about injection of substrate.

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