How it’s made – Bowling Balls
An adult league bowling ball can weigh up to 16 pounds and fully half of the heaviness comes from a weight block that’s hidden inside the ball. The added weight does help knock down more pins but it’s real purpose is to help the
bowler hook the ball to get a strike. This stuff may look like melted chocolate but it’s really the liquid resin that gets molded into the weight block or innermost part of the bowling ball. The resin is polyester based and it can be molded into just about anything. But it’s not very heavy. So heavy minerals like iron oxide and barium are mixed into the resin to help pack on the pounds. Once the minerals are mixed in the resin is pumped out of the mixer and into molds to make the weight blocks. But check out the shake it might surprise you that some weight blocks aren’t even sort of round like a bowling ball. In fact these ones are shaped more like a block. That’s because weight blocks come in two basic shapes; symmetrical and asymmetrical. The symmetrical ones like this round weight block make the ball roll in a straight line which is good for a beginner but not so good for hooking the ball to get a strike. So expert bowlers prefer oddly shaped or asymmetrical weight blocks that distribute the weight unevenly inside the ball. That’s so they can use the weight to spin the ball and make it hook into the pins with more impact.
Regardless of the shape it takes just six minutes for the resin to harden enough for a worker to pop the weight blocks out of the molds. But the blocks aren’t quite ready to go into the bowling balls just yet. First they have to tumble through a rock filled shaker that uses the sharp edges of the rocks to shave off any blobs or seams that could be left on the blocks from the molding process. Then the blocks bounce through a good cleaning car wash style. Remember the blocks way five-day pounds a piece or half the weight of the finish ball, so it takes a lot of jiggling by the conveyor to keep them moving through the washer. When they’re fully scrubbed the blocks spill out of the washer and rest for 24 hours to give the resin time to fully harden.
In another part of the factory another mixer mixes up a different batch of resin that sort of looks like bubblegum instead of chocolate. It’s for the core of the bowling ball or the middle layer that sits between the wait block and the outer shell. While the resin is mixing workers prepare the molds for the cores by placing a wynt block into each one. For this batch they’re using rounder more symmetrical weight blocks that will make the ball hook more gradually. when the blocks are in place the molds are closed up and the pink resin pours in to completely fill in the space around and under the weight block. When the cores are dry adi knobbing machine shaves off the irregular knobs or ribs that are left over from the molds. Then the cores take another tumble through the rocks to smooth out their surfaces. Before they’re closed up in a third and final mold that forms the balls hard outer shell. The shell is made of a dense but rubbery plastic called urethane that can be made into almost any color and a mix of colours. In this case blue black and red squirt into the molds and slosh around to create the crazy swirling patterns you see on some bowling balls. It takes just five minutes for the urethane to harden enough for the balls to come out of the molds. But before they harden completely a hole is drilled in each ball. It’s not for your fingers instead it marks the position of the weight block inside the ball so your pro shop knows where to drill the finger holes for maximum hook.
After the holes are drilled the balls harden for a full 24 hours. Once they’re fully cured like these aqua colored balls the hole is filled with a colorful resin to permanently mark the spot and that’s why you always see a colored dot on a bowling ball. A lathe smooth down the dot and the surface of the ball until it’s a perfect sphere. Then each ball goes through a weight defying test to find its center of gravity. An air jet spins the ball until the heaviest part as determined by the weight block naturally settles to the bottom. That’s the ball center of gravity. A worker marks it with a pin and later on pro shops use the marking along with the dot to determine where to drill the finger holes on each ball. But before the bowling ball ship out they spin through a tunnel of rotating buffers that are coated in a substance like shoe polish to give the balls their super high-gloss shine. Then each ball is engraved with the model name a unique serial number and a permanent mark at the center of gravity. A smear of bright colored paint helps the engravings stand out. The extra pink washes off in a machine that spins the ball under a stream of hot soapy water. Then the finished bowling balls are ready to strike.