I’m looking for ways to add bounce to old tennis balls. Some searching turned up a post where Smeghead mentions that there are screw-top cans designed for this purpose. I haven’t been able to find any, however. Are they still commercially available? Do they have a specific name? Are there any other good methods?
The screw-top containers don’t add pressure particularly, they slow/stop the rate of pressure reduction while in the can.
I have seen a re-pressurizer advertised in the several hundred dollar range. I doubt they are much use – if they were really successful, why don’t the indoor tennis clubs use them?
One bump before I convert my current inventory into chewtoys for the local dogs.
Chewtoys. Tennis balls are so bouncy because they are pressurized with CO[sub]2[/sub]. At manufacture, a pellet of a carbonate compound is sealed up inside, and the gas is released by heating it. Under pressure, the gas slowly diffuses through the rubber. Theoretically, storing the balls under pressurized CO[sub]2[/sub] will restore them, but it’s sloooooooooow, since the rate of diffusion is pretty low.
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- You mean like this?
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http://tennis-balls.com/tennis_ball_chargers/tennis_balls.htm
- I did see a small cheap one somewhere that was a little hand-held deal that only held three balls at a time, but I can’t find it online right off.
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Cool, thanks DougC. It looks like old balls are a lost cause, but one of those gizmos might be able to prolong the lives of new ones.
Maybe.
I’ll see if I can find some independent reviews before I invest $118.
You might want to try posting a question on the message boards at www.tennis-warehouse.com. There are some very knowledgeable tennis players there. There is even a forum just for tennis balls, under the Miscellaneous forum.
Tennis ball pressurizers can be found at your local sports store. They cost only a few bucks. I had one years ago. They look sort of like a tennis ball can, but with a screw top that seals in the air. They may extend the life of the balls for one or two additional sets, but that’s all. The balls definitely don’t play like new.
Tennis balls are so cheap, why bother? You can get them on sale for less than $2 a can (3-ball can). Kmart and Walmart always have sales. Costco sells a case for less than that. They are popular loss leaders in the sports stores and discount stores. I believe that the wholesale price of a can of balls is about $1.90, and I have bought them even cheaper than that. It is amazing that the price of these have not gone up at all in all the years I have been playing tennis, which is almost half a century.
sorry, couldnt resist.
question for Q.E.D… if pressurized at a high enough pressure, would that “recharge” the tennis balls quicker? or is the diffusion rate independent of the outside pressure?
Don’t forget that the other main factor in deterioration of tennis balls is loss of felt. You’ll get that after 2 or 3 sets anyway and that can’t be fixed. I’d fork out the $2 for a new can.
Yes, the higher the pressure differential, the more rapid is the diffusion rate. Likewise, the smaller the gas particles, the faster they wilol diffuse. So, using hydrogen or helium at high pressure will work a great deal faster than CO[sub]2[/sub] will at the same pressure (but also won’t last as long before needing recharging). Also, since it’s partial pressure that matters most, filling them with nitrogen instead of CO[sub]2[/sub] would keep them pressurized longer. I wonder why they don’t actually…
They do. They’re a little more expensive though…about $5 a can.
Nitrogen is more expensive? Well, because it’s so rare, right? :rolleyes:
Yep. I can’t remember the last time I saw some.
More of a supply-and-demand kind of thing–there are many more uses for CO[sub]2** out there, so it’s cheaper.
If you really want to pressurize your balls, you could find a homebrewer with a kegging system and try to sweet-talk him into using one of his spare soda kegs as a ball-pressurizer, so instead of force-carbonating beer he’s force-carbonating tennis balls. He might do it just for bragging rights amongs his homebrewing friends.
If you can’t find somebody with a home kegging system, you have to do it the old-fashioned way which involves champagne yeast, corn sugar, water and a bunch of crown caps, but I don’t think you’ll like the results (the occasonal exploding tennis balls, although amusing, can be a pain to clean up).
Okay, how do they get nitrogen into the balls? I can’t think of any compounds off-hand that will give off nitrogen when heated like they do with CO[sub]2[/sub] balls… Liquid nitrogen would work, but then we run into problems with it’s temperature as it expands…
Why would anyone want to do that? 
But yeah, I agree, shell out $2 for new balls, sheesh.
I don’t know exactly how they do it, but they could keep the balls in a high-pressure nitrogen atmosphere for an extended period and let the gas diffuse into them. I doubt they do it that way, though.
An efficient method would be to put a few tablespoons of nitroglycerine inside the balls and bang them around for while.
They could also just assemble them in a sealed, pressurized nitrogen environment.