How to start the season with balls that have sat all winter

What happens to padel and tennis balls over a northern European winter

Two processes run all winter, whether you use the balls or not: diffusion through the rubber core and the effect of temperature. Both lower the internal pressure, and both make the ball noticeably more sluggish when you pick it up in March or April.

Diffusion is gradual and predictable. A sealed tube of padel balls loses around 1-2 percent of its internal pressure per month, while an opened ball loses 3-5 percent per month. Over a five-month winter, that adds up to a 5-10 percent drop for sealed tubes and a 15-25 percent drop for opened balls - before we even count temperature.

Temperature is the second factor, and it can make things much worse in unheated rooms. Gay-Lussac's law says that the pressure of a gas falls with temperature. From 20 to 0 degrees, pressure drops by around 7 percent from temperature alone. In an unheated shed or a cold garage, the balls may have sat at 2-5 degrees for months, adding an extra 5-7 percent pressure loss on top of the diffusion loss. When the balls are cold as you take them out, the pressure is lower than it would measure at 20 degrees - but here's an important nuance: the temperature effect is reversible, diffusion isn't. When the ball warms up to room temperature, some of the pressure loss comes back.

Unopened tubes vs opened balls - two different situations

The most important distinction when you're looking at balls that have been stored over winter is whether they're sealed or opened. A sealed tube of padel balls contains a pressurised chamber sealed at the same level as the balls themselves - typically 10-11 PSI for padel and 14 PSI for tennis. That means the pressure in the ball doesn't leak out as long as the seal is intact. Diffusion is minimal and the ball is effectively on pause.

An opened ball is a completely different story. When the seal is broken, the pressure in the tube drops to 1 atm straight away. From that moment the ball slowly leaks through the rubber until the internal pressure meets the atmosphere's. It takes 6-8 weeks at room temperature for a significant pressure drop, and it continues whether the ball is used or not. An opened ball that has sat unused for five months has pretty much reached its end point - there's not much pressure left to lose.

That's exactly why storage matters more than most people think. That side of the problem is covered in our guide to storing padel balls and our guide to storing tennis balls. When it comes to the start of the season, the important thing is to accept reality: an opened ball that has sat all winter is no longer a fresh ball, however good the room was.

Assess your balls by how they were stored

Before you take the balls to practice, make a quick estimate based on where they've been. It gives you a realistic expectation before you're on court.

These figures are estimates based on diffusion physics and Gay-Lussac's law, not lab measurements. They're precise enough to plan with, but not to certify a ball. If you want a real number, do a bounce test once the balls have warmed up.

The 60-second test to do before your first session

Once the balls have been at 20 degrees for 24-48 hours, do a bounce test. It tells you whether the ball is still close to the FIP or ITF requirement.

1. Hold a tape measure vertically against a wall. Mark 254 cm.
2. Drop the ball from exactly 254 cm onto a hard surface. A garage floor, tiled hallway or hard basement floor.
3. Measure the top of the bounce.
4. Do 3 attempts and use the average.

For a padel ball, the FIP requirement is 135-145 cm. For a tennis ball, the ITF requirement is 135-147 cm. If your winter-stored ball bounces 130-140 cm, it's usable for club and recreational play. If it bounces 115-130 cm, it's for warm-ups. If it bounces below 115 cm, it's finished.

If you want to dig deeper into the bounce test itself, it's covered for tennis in our article on tennis ball bounce and for padel in our article on padel ball bounce. If you want a more thorough home test than bounce alone, see our guide to measuring tennis ball pressure at home.

How to make sensible use of old balls

A winter-stored ball that passes the bounce test at 130+ cm isn't new, but it can still be used. The question is where it fits into your playing day. Three realistic uses:

• The warm-up basket. Balls with a bounce in the 115-130 cm range are perfect for warming up. You get movement and rhythm, and you save your fresh balls for the real session. Plenty of club players use old balls this way and save around €25-55 a year.
• Solo practice sessions. If you're doing solo drills against a wall or with a ball machine, the ball's playing qualities matter less. A winter-stored ball that bounces 125 cm is fine for 30 minutes of serve or volley practice.
• Dogs or kids. Club players usually have plenty of balls that are no good for sport but still fine for play or as dog toys. A winter-stored ball with no serious playing value is still perfect for a game of catch in the garden.

What you shouldn't do is play club matches or tournaments with winter-stored balls without testing them first. Your opponent expects a ball that behaves like an FIP- or ITF-approved one. A softer ball changes the whole rhythm of the game and isn't fair on the quality of the session.

What to do differently next winter

If most of your opened balls are no longer fit for serious play, it's a sign your winter storage could be tightened up. Three concrete changes:

1. Keep opened balls in a heated room. An indoor cupboard, a drawer in the living room or a basement that stays at least 10 degrees. The small difference between 5 and 12 degrees makes storage noticeably better.
2. Buy extra sealed tubes before winter. A sealed tube keeps for up to 18 months, against an opened ball's 6-8 weeks. If you normally open a new tube every third week in club play, two extra tubes stored sealed are cheaper than buying new balls in March.
3. Use an active pressuriser for opened balls. A Pressurebox Pro keeps the pressure constant. That means opened balls you put in it in October still play like club balls in March, because diffusion never got the chance to draw the pressure out. For an active player who wants usable balls again after winter, it's the most direct way to avoid start-of-season frustration.

For the full list of what works and what doesn't for storing padel balls over winter, see our winter guide to padel balls. The tennis version is in our winter guide to tennis balls. Both guides cover what you can do in October to make March easier.

If you want to work out the overall savings of not having to replace your balls after every winter, the maths is in our article on what padel balls cost a year and the tennis version.