BASKETBALL

Basket-balls range in size from 28.5-30 in (72-76 cm) in circumference, and in weight from 18-22 oz (510-624 g). For players below the high school level, a smaller ball is used, but the ball in men's games measures 29.5-30 in (75-76 cm) in circumference, and a women's ball is 28.5-29 in (72-74 cm) in circumference. The covering of the ball is leather, rubber, composition, or synthetic, although leather covers only are dictated by rules for college play, unless the teams agree otherwise. Orange is the regulation color.

Inflation of the ball is based on the height of the ball's bounce. Inside the covering or casing, a rubber bladder holds air. The ball must be inflated to a pressure sufficient to make it rebound to a height (measured to the top of the ball) of 49-54 in (1.2-1.4 m) when it is dropped on a solid wooden floor from a starting height of 6 ft (1.80 m) measured from the bottom of the ball.

From 1891 through 1893, a soccer ball was used to play basketball. The first basketball was manufactured in 1894. It was 32 in (81 cm) in circumference, or about 4 in (10 cm) larger than a soccer ball. The dedicated basketball was made of laced leather and weighed less than 20 oz (567 g). The first molded ball that eliminated the need for laces was introduced in 1948; its construction and size of 30 in (76 cm) were ruled official in 1949.

The Manufacturing Process

Forming the bladder

• 1 The making of a basketball begins with the interior bladder. Black butyl rubber in bulk form (and including recycled rubber) is melted in the hopper of a press that feeds it out in a continuous sheet that is 12 in (30.5 cm) wide and 0.5 in (1.3 cm) thick. A guillotine-like cutter cuts the long strip into sheets that are 18 in (45.7 cm) long, and they are stacked up. A hand-controlled machine selects the sheets one at a time and, using a punch press, punches a 1-in-diameter (2.54-cm-diameter) hole that will hold the air tube for inflating the bladder.
• 2 The sheets are carried on a sheet elevator or conveyor to an assembly line where the air tube is inserted by hand. A heated melding device bonds it to the sheet, which is folded into quarters. Another punch press stamps out a rounded edge and, at the same time, binds the edges to make the seams of the bladder. This bladder is not perfectly shaped.
• 3 The odd-shaped bladder is taken to a vulcanizing machine. Vulcanization is a process for heating rubber under pressure that improves its properties by making it more flexible, more durable, and stronger. In the vulcanizer, the bladder is inflated. Heating by vulcanization uniformly seals the rubber so it will hold air. Completed bladders are stored in a holding chamber for 24 hours. This quality control measure tests their ability to hold air; those that deflate are recycled.

Shaping the carcass

• 4 The bladders that withstand the 24-hour inflation test are conveyed from the holding chamber to the twining or winding department. They make this joumey suspended from a conveyor system by their air tubes. Machines loaded with spools of either polyester or nylon thread or string wrap multiple strands at a time around each bladder; this is the same process used to make the inside of a golf ball. The irregularly shaped bladders now begin to take on a better, more rounded shape as the precisely controlled threads build and shape the balls. The quality of the thread and the number of strands determine the cost and quality of the ball. The typical street-quality basketball has a carcass made of multiple wraps of three strands of polyester thread. The balls used by professional teams have carcasses constructed of nylon thread that is wrapped using four strands of thread. The same over-head conveyors continue carrying the carcass-encased bladders by their air tubes to the next step in the process where the carcasses and covers will meet.

Crafting the covers of the balls

• 5 Meanwhile, the exteriors or covers of the balls have been in production as the bladders and carcasses have taken shape. On 60-inch-long (152-cm-long) tables, colored rubber is unrolled from a continuous roll. The smooth rubber does not have pebbling (small bumps) that characterizes the surface of a finished basketball so that the outlines for the panels can be clearly marked on the rubber. A silk screen is moved along a series of metal markers that are guides marking the length of the rubber sheet needed for each ball. The silk screen operator moves the screen by hand and imprints the outlines of the six panels making up the ball. Only one color is used at a time, and, depending on the design, multiple silk screenings may be needed to color the six panels with all the colors on the ball.
• 6 A hand-operated punch press—equipped with specially designed and tooled dies—punches the rubber outlines to create six separate panels per ball. The same die has a hole that is punched in one of the six panels to make an opening for the air tube. The excess rubber surrounding the panels is lifted off the line and deposited in a bin for recycling

• 7 The assembly worker picks up the six panels for a single ball in a specific order and carries them to the vulcanizer. The interior of the vulcanizer for this process is different from the one for the bladders. It is form-fitted to hold the six panels, to create the channels between the panels, and to add any embossed information. The assembler fits the panels individually into specified sections in the vulcanizer. A bladder/carcass is taken off the overhead conveyor, covered with a coating of glue, and placed inside the chamber of the vulcanizer that is lined with the cover panels. When the ball emerges from the vulcanizer, most of its surface is still smooth (there are no bumps, called pebbling), but the channels and any embossing are formed into the surface.
• 8 Decals and foil decoration and information (if any) are applied by hand with small heat presses after the smooth ball is retrieved from the vulcanizer. Each ball is carefully inspected for gaps between the panels. These can occur, but each gap is filled during this inspection with a small piece of rubber that is hand-cut to fit the gap. The ball then is fitted into another vulcanizer that unifies the finished surface, blending in any gap fillers, and is specially molded to form the surface pebbling. The vulcanized balls are stored again for 24 hours in a second test to make sure they hold air.

Synthetic laminated covers and leather covers

• 9 The covers for basketballs that are made of synthetic laminated rubber or leather are also made in panels that are die-cut like the rubber panels. The synthetic laminated panels are shaved or trimmed along the edges, fitted and glued together by hand, and laminated to the carcass to create channels. They are also embossed by a heating process and decals are added. Any glue traces around the edges are removed, and any imperfect panels are replaced in the final inspection of synthetic laminated covers. Leather covers are made of full-grain, genuine leather and are stitched with heavy-duty machines; instead of indented, formed channels, the stitching forms the channels in leather balls. They are printed by silk screening and foil stamping, and their inspection includes a review of the uniformity and color of the leather.

Final testing, inspecting, and packing

• 10 Balls that pass the second 24-hour air pressure test are "bounce tested" to meet the regulation for inflation pressure that results in each ball bouncing a prescribed height. Balls that pass the bounce test are numbered to show the production run, and the decals and other artwork are inspected and touched up by hand as needed. Each completed ball is inspected again. The inspector removes the production run tag, and the ball is deflated so it can be easily packed and shipped. Each flattened ball is packed in a polyethylene bag, and the bagged balls are boxed for bulk shipment to the distributor. The distributor also inspects the balls when they are received and is responsible for reinflating them to the correct pressure and packaging them in display boxes for sale. The display boxes may also be packed in bulk for distribution to retailers.