I was looking at some bathbombs in Wally World and they were as hard as concrete ( really hard and smooth) My DD had used them in the past and said they were great. Lots of fizzing action and strong aroma. As always when perusing B&B products I read the ingredient list and aside from the usual, Citric Acid, Sodium Bicarbonate, fo and color it had this sodium sesquicarbonate listed. I googled it and as far as I can tell it is very similar to the bicarbonate and " The Chemistry Store " sells it. Has anyone used it in their bombs yet? I was curious if prehaps this was the secret as to how hard their bombs are??