Q gives a low whistle. "Too much is bad, too little can be worse. Balance is harder to maintain than I thought. Something to do with salt, isn't it?"
"Not necessarily Severus" he dares to disagree. "If you put two potions in front of someone, identical in every way save that one is white like milk and the other looks like ink, they'd choose the white one over 80% of the time. Colour is very important. Isn't that one of the reasons you put this stuff in the pumpkin juice instead of the water pitchers?" Q spreads his hands. "S'truth Severus, I swear! Read it in some tourist guide. So you can take it with a grain of salt. Or a dash of bitters if you prefer. Merlin alone knows why though."
"She's said I can use them whenever I like." He's trying not to appear over-eager. "I promise I shan't make a nuisance of myself though."
*wriggles with glee* Now there's a word you do get to use every day! And it's so...so...apt! :D