Pick A Card, Any Card!

The curtain went up in “Heller’s Wonder Theatre” on Broadway to reveal a blindfolded lady comfortably seated center stage. A volunteer from the audience was solicited to “pick a card, any card!” She did so, thinking of course that it was a free choice. It wasn’t. Robert Heller, the premier American magician of the mid 19th century, was highly skilled at “forcing” a card. There was nothing really novel about that, but his revelation of the selected card was truly innovative. Heller resorted to chemical magic! He silently approached the bare-armed blindfolded woman and waved his hands above her. Suddenly a blood red image appeared on her arm, an image of the card that had been selected! The audience burst into thunderous applause.

I learned about Heller’s chemical conjuring from a marvelous book I received as a present. “Scientific Mysteries and How to Produce the Most Interesting Chemical, Optical and Physical Illusions” is for me a true treasure. Published in 1891 in London, the little volume is a compilation of various scientific effects that titillated Victorian audiences on the stage. Not only are some of the “tricks” truly ingenious, they also show clearly that those of us involved in performing chemical magic today may just be reinventing the wheel. A sobering thought.

About twenty years ago I purchased a gimmicked knife designed to create the illusion of slicing halfway through an arm. It came complete with a hidden bulb that could be filled with red food dye to squirt out at the appropriate moment. Why would I be interested in such a “gross” item? There was some method to the madness. I had in mind to incorporate this illusion into a lecture on the history of charlatans, having learned that at one time mountebanks performed the trick and then pretended to heal the cut on their arm with whatever wondrous nostrum they were selling. Actually, I’m not sure how they produced the “blood,” because my gimmicked knife really didn’t work well. The red dye didn’t seem to come from the wound and worse than that, it made a big mess. So I put on my thinking cap and hoped to find a chemical solution to the problem. The challenge was to create the illusion of drawing blood with a knife.

Chemical analysis often involves various color tests. Starch, for example, reacts with iodine to produce a deep blue color, chlorine with toluidine produces yellow, and iron reacts with potassium thiocyanate (KSCN) to form a “blood red” color. The latter is a very sensitive reaction and is commonly used by criminologists to test for footprints. Most soils will contain some iron compounds which stick to the bottom of shoes. Footprints that are invisible to the naked eye can therefore often be visualized by spraying with a solution of potassium thiocyanate.

Thinking that I was very clever, I decided to apply this reaction to my knife problem. I made a dilute solution of iron chloride (FeCl₃) and rubbed some on my arm. After drying, it became invisible. Then I dipped the knife in a solution of potassium thiocyanate and was ready for the effect. I even had some patter for this, suggesting to the audience that the knife had to be disinfected before proceeding with the dangerous experiment. Lo and behold, it worked! The illusion was amazing. The knife seemed to slice right into my arm, producing “blood” appropriately. I was proud of my ingenuity.

Then I realized that it had all been thought of before. My hundred-year-old book describes Robert Heller’s illusion in detail. Using a camelhair brush dipped in “tincture of perchloride of iron,” he drew the desired image on the lady’s bare arm. Hidden in the magician’s hand was a small bulb filled with a solution of “potassium sulphocyanide” (KSCN) which he sprayed on the arm while waving his hands around in the time-honored fashion of magicians. And why did the lady have to be blindfolded? Simple. To protect her eyes from the chemical spray!

@JoeSchwarcz