https://phys.org/news/2018-05-fifa-world-cup-game-balls.html > On behalf of FIFA, Empa has been conducting the incorruptible series of tests on footballs striving for the FIFA quality program's seal of approval for 22 years. Not every ball passes the test. It is not only the circumference and weight of the ball that are measured precisely. In addition, despite being crushed 250 times in a water tank, it may only absorb a minimal amount of liquid, must be able to hold its air and always jump off at the same height when it impacts from a height of two meters. To prove that it is a perfect sphere, the ball is also measured at no less than 4'000 points. And finally, the ball must retain its shape even if shot against a steel wall 2'000 times at 50 kilometers per hour. > Such standards also determine the quality and consistency of the sport. When the test series were introduced, not all manufacturers succeeded in achieving the required properties: "Time and again, specimens failed, " recalls Camenzind. Some leather balls had increased in size considerably after the procedure or absorbed too much water. Today's balls are glued or welded, because traditional seams could give way over time. Likewise, most of the traditional leather has given way to plastics, the surface of which is specifically textured, which should enable the ball to be guided more easily, especially when the field is wet.