Studious gamblers will investigate and pursue any phenomenon that promises to give them an advantage in the game, however slight. While it is undeniable that a player who can read clumps and track shuffles will gain an additional advantage in the game, these techniques require such intense and constant scrutiny and calculation that they are nearly impossible to practice without using the track of other, more effective, techniques and strategies.

A player would need to have the most extreme mental discipline to use these techniques effectively. To track shuffles and read clumps, meanwhile keeping track of the count, meanwhile employing a wagering strategy, meanwhile keeping a perfect recall of all 270 possible situations and the proper responses, would require intelligence and attention to detail that’s considerably above even “above average.”

In the few occasions when using there techniques, subversion is always necessary. The player may have concentrated on keeping the count while using covert means (a hidden calculating device, or other observers to signal him) of reading clumps and tracking the shuffle, or vice versa. As both calculating devices and signalling are against house rules in most casinos (and the laws in most locations), players risk far more than their wager when using them.

Clump Reading

After three to five shuffles, clusters of high cards will begin to form in deck or shoe of decks, and these “clumps” will become larger and more pronounced as the cards are kept in use unless some deviation in the shuffling technique is used to counteract clumping. The phenomenon is most pronounced in multiple-deck games where the table is full—and in these situations, a player who tracks the clumps, even if he must abandon counting cards to do so, will have an advantage.

You can witness clumping by observing the game in a casino: some rounds seem to consist primarily of high-value cards, others of low, and others seem mixed, in patterns that are too regular to be the result of a truly random deck. If you require further evidence, assemble a deck of playing cards from two of different design (one blue, the other red)—using the 2-6 cards from the blue deck and the 7-ace of the red. Deal out four hands for players, plus one for the dealer. Execute the players’ hands according to basic strategy (the dealer’s according to house rules) and return cards to the discard rack as the dealer would. Use a standard shuffle, cutting the cards in the middle and riffling them three times, then cutting them again before dealing. After five shuffles, spread the cards face down. You will see segments in the deck where the red cards are clumped, where blue cards are clump, and where they are almost perfectly interspersed.

Clumping occurs because of the way dealers place cards in the discard rack at the end of each hand.

A player will most often hit a dealt hand of two low-value, and risks busting the hand, at which point the dealer will immediately return the hand (primarily low cards) to the deck. When a few players bust, this creates a clump of low-value cards in the discard rack.
A player will most often stand on a dealt hand of two high cards. Since all collecting these cards occurs at the end of the game, this creates a clump of high-value cards.

The effect increases when all players at a table follow basic strategy, generally hitting or standing on their hands in reaction to the dealer’s up-card. For example, if the dealer shows a six, all hands will stand on a low total, and if the dealer shows a face card, all hands will hit until they exceed seventeen.

A standard casino shuffle merely offsets these clumps. Unless the cards are stripped (randomised top-to-bottom by dropping a few cards off the top or bottom and re-stacked), plugged (cards that were not played are placed into various locations of the discard rack), or washed (spread out and mixed face-down), the clumps remain together. Additionally, an unbalanced rifle (when cards divide into two stacks that are uneven) will keep even more of these cards closer together, precisely as they were discarded from the previous shoe.

Each riffle intersperses the cards, placing only one card between two that had been together; each cut determines which clumps riffle together. If two high-value or low-value clumps riffle together, this will result in an even larger clump. If high and low cards riffle together, this will have a “zipper” effect, creating high-low-high-low card sequences.

By careful observation of where the clusters exist in the discard rack, how they are cut and riffled together, and how they are cut before play, a player can note the presence of clumps in the deck.

This knowledge can work to the player’s advantage, helping him to deviate from basic strategy when the probable value of the hole card and hit cards decreases its validity. When the upcard is high, but the hole card was dealt from a low-value clump, the player may choose to stand upon rather than hit a low-value hand (because the dealer has a stiff hand that’s likely to break, rather than the pat hand that strategy anticipates). When the upcard is low, and the hole card was dealt from a low-value clump, the player may choose to hit rather than stand (because the dealer has two low cards, which will most often become a strong hand rather than breaking).

Also, clumping is the reason that every card counter has at least one story about a session in which he lost a great deal of cash even though the count was high. Knowledge of the location of clumps will help to avoid these incidents in situations where the order of the deck would usually counteract the counting strategy. For example, if dealing a clump of low cards, the count is high, and a player would typically “bet up”—but if the low-value clump is large (or two are in proximity) the next round will not be to the player’s advantage at all, and the player should not increase his wager.

Since clumping decreases the efficacy of basic strategy and defeats card counters who cannot read clumps, it is unlikely that casinos will alter the shuffling procedure to eliminate this phenomenon. Quite the opposite: if the shuffling procedure is altered at all, it will be to maximise clumping, which will increase the house’s hold on the game until a large number of players abandon counting in favour of tracking clumps.

Shuffle Tracking

Shuffle tracking is a technique that a player can use to keep track of certain cards in a deck. In theory, it is possible to predict the exact location of every card that has been seen on the table by noting their values as they are returned to the rack and the way in which they are shuffled before being put back into play again. In practice, it would be an astounding feat of mental dexterity to do so—but an attentive player can keep track of the cards that matter, i.e., tens and aces.

It is possible to track shuffles because most dealers handle the cards in simple patterns, predictably dividing decks and riffling them perfectly so that the cards alternate one-to-one from each stack. For example, a two-deck rack of cards may be cut and riffled three times. This places an average of five cards between any two that had previously been dealt together (unless the deck was divided between them).

By careful observation, the user can track cards that have been dealt by either (or both) of two methods:

First, by knowing the “depth” of the tracked cards in the deck, the player can cut the cards so that they will be kept in play by making sure that, after the cards are cut, these cards are in front of the cut card when it is reinserted into the stack.

Second, the player can predict, whether by death or by “key” cards, when the tracked cards will show. If judging by depth, the player may know that one or more tracked cards will come out in the next hand depending on the number of cards that have been dealt. If referring to key card, the player may know that an ace is a certain number card behind another card that was returned to the rack, and thereby know which player (or the dealer) will receive the tracked cards in the next deal.

The ability of a player to increase his wager when he knows, as an absolute certainty, that an ace will be dealt with him in his next hand, will shift the odds in his favour. Without knowing the value of any other card, there is a 31% chance he will draw blackjack (and receive a 3:2 payoff)—and even if he does not, there is a high probability he will be able to draw to 17 or better without busting.
Casino Countermeasure: Shuffling Machines

The use of shuffling machines in some casinos is an effective countermeasure to both of these techniques. Because the machines are opaque, it is not possible for a player to observe the way the cards are being cut and shuffled—thus both shuffle tracking and clump reading are impossible.

These machines are not wholly disadvantageous to the player. Unlike the manual shuffle, which moves each card only a few places in the deck, a shuffling machine chooses each card at random. The result is a shuffled deck that is random—or as random as is mechanically possible. If clusters of cards occur, they will not (necessarily) be preserved, and certainly not amplified, throughout several shuffles.

While this negates the player’s ability to track specific cards or clumps of cards, it also negates the house’s ability to stack the deck by using unbalanced shuffles to create, preserve, and amplify clumps that are advantageous to the house. As a result, the player can expect the basic strategy to work as it is intended, and can still count cards to obtain shift the odds further in his favor.