Jon Carroll went to his granddaughter's science fair and noticed a significant absence.
Someone asked me if there were any mock-ups of exploding volcanoes at the fair. There weren't, and I now wonder whether the exploding-volcano-at-the-science-fair riff isn't some kind of urban legend. Certainly, hilarity ensues, but did people ever actually do it? Maybe the hilarity is bogus, Hollywood hilarity.
I can vouch for the regular appearance of exploding volcanoes at science fairs when I was growing up. They were indeed amusing, even if what made them explode wasn't really what makes real volcanoes erupt. Someone in my circle of friends once dreamed up the idea of trying to make one by duplicating actual geologic stresses with clay and heat, but good sense made a rare appearance and nixed it.
In any event, it certainly isn't happening now. Do you know what liability insurance costs these days? Do you know how litigious parents can be? Science fair volcanoes are an artifact of another century, or of the fantasies of another century. You could still build a big papier-mache volcano; you just couldn't make it do anything. "My project is an extinct volcano. Thousands of years ago ..." Hilarity fails to ensue. Also: Eye injuries fail to ensue. It's a trade-off.
For a kid there's nothing like a chance to engage in officially sanctioned destruction. I recall a classmate doing an experiment that involved using a car battery for electricity. Of course he managed cross the poles on the battery, producing a considerable amount of smoke and just as much mirth. I recall a dubious claim that it was an accident, but the pliers seemed suspiciously well-melted.
One year a couple of friends and I tried to build a carbon dioxide laser. Yes, a laser. As I recall we got the design from Popular Science or some similar magazine. Since there wasn't a local source of CO2, we had dry ice shipped in, which itself provided plenty of hilarity, such as chasing my brothers around with a glass of bubbling and steaming CO2-cooled water, threatening to make them drink it while withholding the fact that since the dry ice had evaporated it would be harmless. Flushing small pieces down the toilet also provided entertainment.
We actually managed to assemble the necessary components (try explaining a semi-polished mirror to someone, much less making one. I'm not sure I completely understood it.) and get it running momentarily, but our cooling system (a tiny electric motor with homemade fan blades) proved inadequate and the tube cracked with a loud POP. I think we got a C on the project for sheer audacity. It really was amazing that we got as close as we did with what we had. There is something to be said for the value of just not knowing any better.