I'm Doc Braun, and as that name probably suggests, I'm a movie buff as well as a chemistry enthusiast. I've joined up initially to ask one question. I've asked it elsewhere, but not got a solution that I can really use. I make amateur films. I'm currently planning one in which a scientist builds a Time Machine and requires a very powerful source of energy to operate it. He's a turn-of-the-century (the 20th century, that is), guy, so he doesn't have access to nuclear fuel. But he believes he can "unlock the power of the atom" by chemical means. To that end, he experiments with mixing various chemicals, but they're all duds. But then he mixes two chemicals and the reaction is dramatic, and he realises he has his fuel. Now to my question. I need to know two chemicals which, when mixed, will give me that "dramatic" reaction. Mainly, I want visible fumes to rise and perhaps the colour to change as well. Obviously, I do not want hazardous chemicals, since I'll need my actor for the rest of the movie... Can anyone suggest any substances that would serve the purpose, and be totally safe to handle? EDIT: I can't use strong acids or anything highly flammable, because it is a small indoor set, with no ventilation for hazardous gases/fumes/smoke. Thanks.