The Unbalanced Shuffle of Blackjack
An unbalanced shuffle results when the dealer splits the deck irregularly before shuffling. For example, the dealer's pick A, the top portion of the deck, consists of, say, 32 cards, and pick B, the bottom portion of the deck, consists of 20 cards. The dealer makes similar unbalanced picks with each hand throughout the shuffling process and, as a result, up to 12 cards of the upper portion of pick A are not intermixed with pick B. It is possible for the top 12 cards in the deck to be preserved throughout the shuffle.
Blackjack dealers commonly use the unbalanced shuffle to foster excessive clumping and inhibit distribution. When new cards are introduced, because of the way card manufacturers package the cards (ace through king of one suit, king down to ace of the next), like cards tend to clump together, even after the casino "wash." This like-card clumping is very detrimental to the player, and some casinos look for shuffles that will prolong such like-card clumping as long as possible. While many dealers inadvertently make unequal picks, some dealers are required to do so because an unbalanced shuffle is the house shuffle, one that is dictated by management. When fresh decks of cards are put into play at houses that dictate an unbalanced shuffle, like-card or similar-card clumping is likely to persist because of the shuffling process.
The unbalanced shuffle can be exploited if the dealer is consistent with unequal picks. The end-of-deck count from the previous game would give you good information about the unplayed cards that potentially represent an identifiable clump. If the unplayed cards are placed on top of the deck prior to the shuffle and the upper portion of the deck remains the dominant pick, then you are in a position to retain or eliminate the clump with the cut card. If the clump includes an excessive number of low cards unfavorable to the player, and you are able to get the cut card, cut these cards out of play so the dealer will place them at the bottom of the deck. Of course, high cards favorable to the player would be retained.
While some dealers will readjust the size of their picks if you ask them, an occasional toke or tip for the dealer prior to the shuffle may encourage a more favorable shuffle without making you conspicuous because of your request. In houses in which dealers must follow a prescribed shuffling procedure as far as the picks are concerned, dealers will not change. Their response will be, "I'm sorry, I must follow the house shuffle." Your only recourse is to find another dealer, or another house.