Oh, I'm not brewing, exactly. Mr Snape has three versions of a potion he wants me to test for all sorts of things, like solubility and whether they'll react to other common potions. The thing is that once you start you have to watch for it to behave in certain ways, either expected or unexpected.

And listening's not a problem. If one of you says something wrong I'll probably notice, even if I'm glued to a potion to see if it turns green after a minute or whatever.