Svengali deck
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The Svengali deck of cards is a specially constructed deck that can be used by magicians to perform various card tricks. The deck and the tricks performed with it are self-working and require almost no skill. Burling Hull (Volta the Great) claimed to have invented the deck in 1909.
The magician can allow a spectator to choose what seems to be a random card from the deck, while actually forcing the spectator to choose a card known to the magician. The deck can give the appearance of being a normal deck, or of a deck consisting entirely of identical copies of the same card.
Twenty-six of the playing cards in a Svengali deck are a mixture of various suits and denominations, similar to those in an ordinary deck. The remainder of the deck is comprised of twenty-six identical copies of the same card; for example, the eight of diamonds. These are the force cards. The force cards are trimmed very slightly shorter than the others, and the deck is arranged so that force cards alternate with normal cards.
The result of this construction is that when the deck is riffled, the thumb contacts only the longer, normal cards.
Svengalideck.png
Diagram showing operation of Svengali deck
The diagram shows a deck of Svengali cards, the red lines representing the force cards and the black lines representing the ordinary cards. (The differences in length are greatly exaggerated in the diagram; in the real deck the difference in length is almost imperceptible to the eye). Assume the cards are arranged with their faces down and their backs up. The card lifted by the thumb is always an ordinary card. The card lying face down on the portion of the deck below the thumb is always one of the force cards.
One way in which the magician can force a card is to riffle through the deck, and ask a spectator to select a card by inserting a finger and stopping the riffle at any point. The spectator always selects one of the force cards.
The deck can also be cut at any point, and the bottom portion of the deck will always have a force card on top.
When the deck is riffled with the thumb moving upward, toward the backs of the cards, during the riffle only the faces of the ordinary cards are visible to a spectator. The fact that half of the cards are force cards is not detectable, and the deck thus gives the appearance of an ordinary deck of mixed cards.
The magician can deliberately riffle the cards in the opposite direction, with the thumb moving down, toward the front of the cards. The action of the deck is reversed. Only the faces of the force cards are seen. The ordinary cards are hidden, and the deck gives the visual appearance of consisting solely of copies of the force card. This can be a dramatic flourish, but it also gives a dangerously explicit clue about the nature of the deck.
One obvious weakness of the Svengali deck is that the magician may not allow the deck to be examined by the audience. Another weakness is that the Svengali deck is about a century old, very well known, and sold in novelty stores; audiences are likely to include members who are familiar with it.
External links
- Svengali card tricks (http://web.superb.net/cardtric/sleights/svengali.htm)
- Making your own Svengali cards (http://www.cs.wisc.edu/~roy/magictalk-wisdom/discussions/making_svengali_cards.html)