It certainly is, but I've found (after waiting and waiting for the bottles to do their thing) that some issues have cropped up in various bottles. This has been really disappointing; but I've had a few good bottles so far - although they've turned out to be a little more .... erm, potent than expected!

I really need to find a source of good, cheap glass bottles as I've had problems with some of the plastic soda bottles I've (re)used.