Ping pong balls are made by molding two hollow half-shells from plastic, bonding them together, and then machining the seam smooth. The process sounds simple, but getting a 2.7-gram sphere to meet tournament standards for roundness, weight, and bounce requires surprisingly tight manufacturing controls. Here’s how it works from raw material to finished ball.
The Shift From Celluloid to Plastic
For over a century, ping pong balls were made from celluloid, a semi-synthetic material derived from plant cellulose mixed with camphor. Celluloid gave the ball its signature feel and bounce, but it had a serious problem: it’s highly flammable. Shipping and storing large quantities of celluloid balls posed genuine safety risks, and growing regulations around the world threatened to make them illegal in some countries.
In 2014, the International Table Tennis Federation officially switched the approved material from celluloid to a non-celluloid plastic. Modern balls, often labeled “40+” on the packaging, are typically made from a type of polymer plastic (most commonly a form of ABS, or acrylonitrile butadiene styrene). This newer material is far safer to transport and store, though players noticed subtle differences in bounce and spin behavior during the transition.
Forming the Half-Shells
Production begins with small sheets or pellets of plastic. In one common method, thin plastic sheets are softened with heat and then pressed into hemispherical molds to create half-shells, each one forming exactly half of the finished ball. Some manufacturers instead use injection molding, where melted plastic is forced directly into a mold cavity to form each half. Either way, the goal is two perfectly uniform cups with consistent wall thickness, typically less than a millimeter.
The quality of this first step determines everything that follows. If the wall thickness varies from one side to the other, the ball will wobble in flight. If the hemisphere isn’t perfectly round, no amount of finishing can fix it.
Bonding and Seaming
Once the half-shells are formed and trimmed, two halves are joined together. Older celluloid balls used an adhesive to glue the halves, but many modern plastic balls are thermally bonded, meaning the edges are heated until they soften and then pressed together to fuse into a single piece. Some manufacturers still use a solvent or glue-based process, depending on the plastic formulation.
After bonding, the seam is clearly visible as a raised ridge circling the ball’s equator. Workers or machines then sand and polish this seam until it sits flush with the rest of the surface. A poorly finished seam creates air resistance on one side of the ball, causing unpredictable flight paths. On high-quality balls, you can still see where the seam is, but you can barely feel it with your fingertip.
Finishing the Surface
After seaming, the balls go through a tumbling or polishing process to create a uniform matte finish across the entire surface. This texture matters for gameplay because it affects how much spin a paddle can impart on the ball. The balls are then printed with the manufacturer’s logo and given their characteristic white or orange color, either through the plastic itself being dyed before molding or through a coating applied afterward.
How Quality Control Sorts the Stars
Not every ball that rolls off the production line is equal, and that’s by design. Manufacturers sort finished balls into quality tiers, marked by a star rating from one to three. The difference between a casual rec-room ball and a tournament ball comes down to how tightly each one meets a set of physical standards.
A 3-star ball, the highest grade, must weigh 2.7 grams (with a tolerance of just plus or minus 0.1 grams), measure 40 millimeters in diameter (within 0.2 millimeters), and be perfectly round. Each ball is individually tested. The bounce test is especially telling: when dropped from 30 centimeters onto a hard, flat surface, a 3-star ball must rebound to between 23 and 26 centimeters, and it must do so consistently across repeated drops. Only balls meeting all these criteria earn the 3-star label and approval for use in official ITTF matches and professional tournaments.
Two-star balls offer better consistency than the bottom tier and work well for club training and local competitions, but they allow slightly wider tolerances. One-star balls accept minor irregularities in shape and weight, producing variable bounce properties. They’re perfectly fine for casual play but wouldn’t pass the precision checks required at higher levels. In practice, a factory might produce thousands of balls in a single run, and the sorting process determines which tier each one lands in based on how close it came to perfect.
Why Seamless Balls Exist
Some manufacturers have developed seamless ping pong balls, which are molded as a single piece rather than two halves joined together. The process typically involves injecting plastic into a spherical mold with a dissolvable or removable core inside. Once the shell hardens, the core is removed, leaving a hollow sphere with no seam at all.
Seamless construction eliminates the biggest source of inconsistency in traditional balls. Without a seam, the wall thickness and surface texture are more uniform, which produces a more predictable bounce and flight. These balls tend to cost more because the manufacturing process is more complex, but they’ve become increasingly common at the competition level.
What Makes a Ball Feel “Right”
The interplay of wall thickness, material stiffness, and diameter determines how a ball responds when struck. A thicker wall makes the ball harder and produces a sharper, faster rebound. A slightly softer material absorbs more energy on contact, slowing the ball down and changing the sound it makes. Players who lived through the 2014 material transition often describe the newer plastic balls as slightly larger-feeling and slower, with less spin potential than the old celluloid version. The physics backs this up: studies comparing the two materials found measurable differences in how the ball behaves after bouncing off a surface.
For casual players, these differences are barely noticeable. For professionals who train thousands of hours around the precise physics of ball behavior, even a fraction of a millimeter in diameter or a tenth of a gram in weight changes the game.