There have been plenty of people on tv over the years who have revealed how magic tricks are done.
A few years ago there was a series, Breaking The Magicians’ Code, Magic’s Biggest Secrets Finally Revealed, where the Masked Magican showed a number of classic tricks, and some not so classic, and showed ways they could be done, complete with sexy assistants:
Penn and Teller have at times shown how some of their tricks were done. There are channels on YouTube with people explaining how tricks on Penn & Teller Fool Us could be done. You can easily find those yourself.
John Lenahan has also explained tricks, and that got him expelled from the Magic Circle, basically a magicians’ union.
Nearly always, the explanation of the mechanics of a trick or illusion get the response ‘is that it?’ Often it’s a bit of elastic or invisible thread, double sided tape, doctored playing cards or something similar. Or maybe some kind of optical illusion.
Just because someone explains how a trick can be done does not mean it’s the only way. Very often, there are multiple methods. They always say you should never repeat a trick, but using different methods can enhance the puzzlement.
You sometimes hear someone say ‘no-one knows how such-and-such a trick is done’, but that’s a lie. Of course people know. The designers and builders of the trick or illusion, the performers, of course they know. It may be kept a secret, but people know.
