TENNIS.com gear editor Justin diFeliciantonio and his technical advisers answer your equipment questions each day. Click here to send in a question of your own.
The other day, I played a few sets with a guy originally from Denmark. He said some interesting things about playing tennis there—notably that everyone uses pressureless balls, which are apparently dissimilar to what we use here. Could you shed some light on this? Why pressureless balls?—Jerome Y.
Generally speaking, Jerome, there are two categories of tennis balls: pressurized and non-pressurized (or pressureless).
Pressurized balls, which are far and away the norm in the U.S., are manufactured with an internal air pressure higher than that of the ambient atmosphere. This additional pressure is what lends the balls their stiffness, bounce, and feel. It’s also why pressurized balls are sold in pressurized cans; once a can is cracked open, and the balls are exposed to the surrounding air, their internal pressure (and playability) begins to slowly diminish. (As The Physics and Technology of Tennis notes, “the rubber walls of most balls are slightly permeable to air,” hence the leakage.) After several sessions, as you know, it’s time to crack open a few new cans.
Non-pressurized balls, on the other hand, don’t derive their stiffness from elevated internal pressure; rather, they bounce because of a thicker rubber shell. For this reason, they don’t go flat. Typically, the pressureless variety are more expensive to manufacture, are sold in cardboard boxes (instead of cans), and are most popular in Europe. In terms of their playability, the general consensus is that they feel and play a bit harder and “deader.”
If you’re interested in comparing the two for yourself, check out online retailers or your local specialty pro shop. While the use of pressureless balls is uncommon stateside, they’re not too difficult to find for purchase.