When looking for "pure ammonia" in the grocery store, hardware store or wherever, look for 100% pure ammonia with no surfactants added. Surfactants are the compounds that create suds and are extremely harmful (they also can't be removed by the nitrifying bacteria like ammonia can be). I struck out at every major grocery store and "box store" (Walmart, KMart, Target, Home Depot and Lowe's), but I did end up finding it at a True Value hardware store. It was $2.49 for a 1 gallon bottle.