I am going to be out of my welding class in a couple weeks for 3-90 minute blocks. During this period I can't have them in the shop. We are well into welding at this point of the year, so plain textbook activities don't seem appropriate. What are some interesting activities that I can have them do with my sub besides watching Modern Marvels? I remember seeing an activity about welding using icing, but can't seem to locate it on here or the web.