Demonstrations are increasingly becoming staple fare in the armoury of physics teachers. Physics is generally perceived to be a difficult subject, so the use of demonstrations to scaffold understanding as well as generate interest among students is valuable. When a demonstration is presented in a mysterious manner, students want to know how it is done and understand the physics behind it. This can be one way to get students excited about physics. In this article, the authors describe one such demonstration involving surface tension and pressure that they have used to good effect in their teaching of trainee teachers. (Contains 6 figures.)