Wait until lunch time

As much as he wanted to have some fun with Parvati right there and simply could blast her with the miniaturized raygun, Harry realized that the others might look after him. So he left the restroom and in a corner of the corridor, stuffed the cloak into his bag again. The next lesson, just before lunch time, was rather boring, beside that Parvati arrived way too late and with her hair a huge mess, which prompted Lavender to ask her again if everything was alright.

Harry heard them whispering and was rather sure Parvati told Lavender what strange things had happened earlier. He didn't tried any more testing until lunch time. As they wandered into the great hall, some students were already sitting around, eating and chatting. Harry wondered if this was a good idea to test the ray gun on some food again. But who? He looked around and noticed that Pansy Parkinson was sitting across the room, drinking from a cup. He got an idea and got up, telling Ron and Hermione he would quickly head to the bathroom.

Outside he once again put on the cloak and headed back in. Pansy had just put the cup down and Harry gave it a quick blast, before heading away again. As he looked over his shoulder, he noted how one of the other Slytherin girls asked Pansy a question and then refilled her cup. This made Harry wonder if it would dilute the effect of the cup's content a bit. Gladly Pansy seemed to haven't drunken anything until he returned to his place, curious what would happen.