Two Deck Location
I’ve got a really nice effect lined up for you today…
Imagine this:
You hand a deck to your spectator.
They riffle shuffle the deck, then cut and remove a bunch of cards. They shuffle the cards in their hand, then choose one of them. A second spectator cuts another bunch of cards from the remainder and does the same. They swap their chosen cards and shuffle the packet in their hands again.
Despite all this, the moment you pick up their shuffled packet—you know both their cards!
Let’s break it down step by step.
- You hand a deck to your spectator
The deck is stacked.
(bet you didn’t see that coming, huh?)
- They riffle shuffle the deck
The spectator can riffle shuffle the deck one time. Thanks to Charles Jordan’s ‘chains’ principle, this won’t affect us as much as it seems.
Here’s how I explained the ‘chains’ principle in the Skyscraper Method:
“After a spectator riffle shuffles a deck of cards once, the cards really aren’t all that mixed.
All you’ve actually done is taken half of the stack and shuffled it into the other half.
Those two halves have been shuffled together, but the individual halves still maintain their order.
NOTE: For this to work, they need to riffle shuffle the cards. To make sure this happens, gesture or demonstrate what to do before you give them the cards.
Perhaps the easiest way to explain this is with an example.
Let’s say you have a deck of 10 cards, numbered 1 to 10.
You take 5 into each hand and riffle shuffle them together.
The end result, from top down, looks like this:
1,
6,
2,
7,
3,
4,
8,
9,
10.
The two halves are shuffled together, but each individual half (1-5 and 6-10) maintains its original order.
Look:
1,
6,
2,
7,
3,
4,
8,
9,
5,
10
If you look at the left hand column and right hand column, we still have cards 1-5 retaining their order, and on the right we have cards 6-10.
All that’s happened is that those two orders have been combined:
1,
6,
2,
7,
3,
4,
8,
9,
5,
Now imagine what might happen if we asked someone to remove a card. Let’s say they removed the 7. If we get them to place it back in a different place, look what happens:
1,
6,
2,
3,
4,
8,
7,
9,
5,
10.
Which is the same thing as:
1,
6,
2,
3,
4,
8,
7,
9,
5,
10.
Notice how there’s one card out of place that would be immediately obvious, even if we didn’t know the identity beforehand?
The 7.”
- They cut and remove a bunch of cards
Make sure they take a smallish packet—between 10 and 20 cards. Then have the second spectator cut another 10-20 cards off the remainder of the deck.
- They shuffle the cards in their hand, then choose one of them
At this point, it doesn’t matter how much they shuffle—the cards in their hand will always be the cards of a particular two chains.
For example, let’s say after the initial riffle shuffle, the top 30 cards of the deck looked like this…
1, (aka the first card of the stack)
2,
3,
30, (aka the 30th card of the stack)
31,
4,
32,
33,
34,
5,
6,
7,
35,
36,
8,
37,
9,
38,
39,
40,
10,
11,
12,
41,
13,
14,
15,
42,
16,
43
Let’s say Spectator #1 cut the top 15 cards off.
She now has:
1,
2,
3,
30,
31,
4,
32,
33,
34,
5,
6,
7,
35,
36,
8.
She can shuffle as much as she likes, but it won’t change the fact that she will ALWAYS have cards 1-8 and 30-36 in her hand.
For example, after shuffling, it might look like this:
34,
2,
8,
36,
33,
3,
4,
32,
30,
31,
5,
7,
35,
1,
6.
Even though the order has changed—she still has cards 1-8 and 30-36.
Now, let’s imagine Spectator #2 cut the next 15 cards off the deck.
That would give him the following cards…
37,
9,
38,
39,
40,
10,
11,
12,
41,
13,
14,
15,
42,
16,
43
No matter how much he shuffles, he’ll always have cards 9-16 and 37-43 in his hand.
For example, after shuffling, it might look like this:
12,
15,
37,
41,
43,
16,
9,
13,
14,
42,
11,
40,
38,
10,
39,
The order has changed, but he still has cards 9-16 and 37-43.
Anyway—I wanted to really make sure you got that, because it’s what makes this whole thing work.
Let’s move to the next step…
- They swap their chosen cards and shuffle again
Let’s say Spectator #1 chose 7, and gave it to Spectator 2. Let’s say Spectator #2 chose 42, and gave it to Spectator #1.
Both spectators can then shuffle their cards again.
Their new packets might look like this…
Spectator #1:
6.
35,
31,
5,
32,
30,
3,
2,
4,
42,
1,
33,
8,
36,
34,
Spectator #2:
10,
39,
14,
9,
15,
12,
16,
40,
43,
11,
38,
7,
13,
37,
41,
Perhaps you can already see how simple it is to figure out which card belongs to who.
Let’s go over that in the last step…
- Despite all this, the moment you pick up their shuffled packet—you know both their cards!
In fact, you only need to pick up ONE of the packets.
Let’s say you take Spectator #1’s cards.
As you look through them, you can see that one card is wildly out of place—42.
But not only that, you can see that one card is missing—7.
Therefore, just by looking at Spectator #1’s cards, you can tell which cards BOTH spectators chose.
The only thing left for you to do is decide how you want to reveal the cards!
I hope you enjoyed this!
This was a fun one, digging back into some core mem deck concepts and ideas.
Speak soon!
Your friend,
Benji