We're posting a new bath bomb this month (officially scheduled for the 27th of February) but along the way, ran into some problems. I was trying to come up with a faster way to dry them out so I could rush the process and cut the time down between molding and testing and thought I'd shortcut by popping a batch in the oven at a low temp for 30 minutes.
Yes, it dried them out in record time...but it resulted in rock-hard bombs that just wouldn't dissolve and left huge chunks of black crunchy sand in the bottom of the tub. Normally a bath bomb takes around 3-5 minutes to really dissolve. These bastards took almost 15 minutes, and even then, never completely dissolved.
Here's a link to the Youtube time-lapse video of the first test sped up over 25X faster than real-time...