Rules of Cricket

In baseball, the ball must remain in a clean and new condition. The ball is replaced frequently to ensure this. If the ball is hit into the crowd, the lucky crowd member keeps it. In cricket, the wearing of the ball is an important part of the game. The same ball must be used until a change of ball is allowed by the rules. If the ball is hit into the crowd, the crowd member must return the ball to the players.

The Cricket Ball

The fielding team is given a new cricket ball at the start of each innings. The ball may not be changed for another ball except under the following conditions:

After 80 overs have been bowled with the ball, the captain of the fielding side may demand a new ball. He does not have to, and may continue using the old ball for as long as he wishes.
If the ball becomes damaged and unfit to play with, or lost, the ball must be replaced by a used ball which, in the opinion of the umpires, is in a similar state of wear to the ball being replaced.

Whenever a ball is changed, the batsmen must be notified by the umpires and allowed to inspect the replacement ball.

Changing the Condition of the Ball

In baseball, the fielding team may not apply any substance to the ball, and making the ball asymmetrical is illegal. In cricket, the fielding team may, and generally do, apply saliva to the ball to make it asymmetrical.

Any fielder is allowed to:

rub or polish the ball, provided no artificial substance is used,
remove dirt or mud from the ball under the supervision of an umpire,
dry the ball on a towel if it is wet.

This means that fielders are allowed to polish the ball on their clothing or a cloth, and may apply saliva or sweat to the ball.

Fielders may not:

rub the ball on the ground for any reason,
lift the seam of the ball,
roughen or scuff the ball in any way, such as with any abrasive material, including fingernails.

Extra Detail: Fielders usually polish one side of the ball, using saliva to keep it shiny and rubbing it on their clothing to keep it smooth. They allow the other side to wear naturally. This asymmetry allows bowlers to get the ball to curve in the air when they bowl it.