"I was having another chat with the house elves. They know stuff," Tobi shrugged. "It couldn't hurt to try." Tobi poked the black board with his wand again, the universal language in the wizading world for, 'do stuff', "have you got anything else to tell us? Please?"

The black board revealed its second clue, confirming Tobi's suspicion that it wasn't a particularly complicated potion. It wouldn't be if they were meant to identify all its ingredients right? Now what was it?

"So it's volatile and its got very few ingredients, do you remember if Shrinking solution was particularly volatile? Perhaps we can confirm or exclude my guess."