Magic smoke

magic number = M = mail storm

magic smoke n.

A substance trapped inside IC packages that enables them to function (also called 'blue smoke'; this is similar to the archaic 'phlogiston' hypothesis about combustion). Its existence is demonstrated by what happens when a chip burns up -- the magic smoke gets let out, so it doesn't work any more. See smoke test, let the smoke out.

Usenetter Jay Maynard tells the following story: "Once, while hacking on a dedicated Z80 system, I was testing code by blowing EPROMs and plugging them in the system, then seeing what happened. One time, I plugged one in backwards. I only discovered that after I realized that Intel didn't put power-on lights under the quartz windows on the tops of their EPROMs -- the die was glowing white-hot. Amazingly, the EPROM worked fine after I erased it, filled it full of zeros, then erased it again. For all I know, it's still in service. Of course, this is because the magic smoke didn't get let out." Compare the original phrasing of Murphy's Law.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

Magic smoke (properly called "Mystic Smoke from fingertips") is also a product sold at many costume and magic supply stores for street performers.

It's not effective on stage, but up close and personal, it makes an impression. It's a resin-based paste that one rubs on their thumb and middle finger ahead of time until it's warmed up and spread around. Then, when a dramatic effect is needed, you rub or snap your fingers and if done right, superfine strands of the resin "magically" float off, off and away.

It looks like you created smoke, wisp, or perhaps spiderweb off your fingertips, and honestly it looks pretty darn neat. It's roughly flesh-colored (a yellow-pink-clear) so no one sees it on your fingers ahead of time. Your skin keeps it warm, so you can produce "smoke" any time until you run out or wash your hands.

However, the observer with the accute sense of smell can tell something's fishy because it has a very distinctive sap-plastic-chemical smell that your skin shouldn't make.

Fascinates small children and their parents; mystifies cats.