Coverstock is defined as the most outer portion of a bowling ball that makes contact with the lane. Coverstock material accounts for roughly 80% of the reaction seen on the bowling lane.
Coverstocks are made out of different types of material.
- Reactive Resin
- Particle Reactive
Each of these materials generate different amounts of friction with the bowling lane, this causing different reactions.
Polyester is the least aggressive coverstock available, thus reacting the least in the oily part of the lane and least on the dry portion of the lane. Plastic coverstock balls are usually reserved for situations where a bowler wants to go as straight as possible, such as spare shooting, or reserved for extremely dry lanes, where control and minimal reaction is a must. Most plastic balls do not come with a core, as having the dynamics of a core inside can be costly to create and have a very marginal benefit on the lanes. Plastic balls with a core tend to cater to a very
Rubber is an old coverstock material from before the 1980's when Urethane was first released. Rubber offers slightly more reaction than plastic, and very similar to urethane. Drilling rubber balls can be an unpleasant and unhealthy experience. During the drilling process the rubber coverstock had the tendancy to heat up from friction due to the drill bit, partially melting the softer rubber shell, emitting a profound odor most can identify with if they've driller a rubber ball.
Urethane began the original "power boom" most bowlers enjoy about the game now. Urethane has greater angle and ability to cover more boards than rubber or plastic coverstocks. The first urethane ball to introduce this type of coverstock was the AMF Angle. The urethane covertock revolutionized the game, and provided the base material for reactive coverstocks that are very popular today.
This category of coverstock is the most popular produced in the world of bowling in this era. Around 1990 manufacturers added reactive resin material to a urethane base to produce a ball that is more aggressive in reaction to friction at the end of a bowling lane. This violent reaction causes the ball to enter the pocket at a greater angle, thus having a greater carry percentage over rubber, plastic and urethane coverstocks. What causes the aggressive reaction of a reactive ball is the resin added to the urethane shell to create mircoscopic pores in the ball, which grab the lane, and make the surface of the ball feel tacky. Without question, reactive covertock bowling balls have assisted in the scoring boom within the sport of bowling since the early 1990's.