# Why are tennis balls sold in hermetically sealed cans? **URL:** \ **Category:** Factual Questions\ **Created:** [March 31, 2009, 12:13pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410 "2009-03-31T12:13:06Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [March 31, 2009, 12:13pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/1 "2009-03-31T12:13:06Z")
Why are tennis balls sold in sealed cans? It’s not like they’ll spoil if exposed to the air (or will they?) I don’t play much tennis, so maybe there’s something obvious I’m missing, but the current mode of packaging seems like overkill to me. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [March 31, 2009, 12:22pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/2 "2009-03-31T12:22:32Z")
Most tennis balls are pressurized, so they can indeed go bad if the pressure leaks out. [Pressurized cans keep them fresh](http://www.itftennis.com/technical/questions/index.asp#2): > [@](#): > > Conventional pressurised balls lose pressure by the process of diffusion and their properties deteriorate accordingly. To preserve these properties until the balls are required for use all good quality pressurised balls are packed in hermetically sealed containers. ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [March 31, 2009, 12:23pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/3 "2009-03-31T12:23:18Z")
I believe that tennis balls are pressurized slightly to give them extra bounce. But they tend to lose pressure over time. Pressurizing the can keeps that from happening. ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [March 31, 2009, 1:28pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/4 "2009-03-31T13:28:31Z")
To keep that intoxicating smell in. Duh. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [March 31, 2009, 1:56pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/5 "2009-03-31T13:56:45Z")
I keep mine in hermetically sealed jars on Funk and Wagnall’s front porch. ---
**Author:** ![RiverRunner](https://avatars.discourse-cdn.com/v4/letter/r/977dab/32.png) [@RiverRunner](https://boards.straightdope.com/u/RiverRunner)\ **Post date:** [March 31, 2009, 1:57pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/6 "2009-03-31T13:57:45Z")
> [@Finagle](#): > > I believe that tennis balls are pressurized slightly to give them extra bounce. But they tend to lose pressure over time. Pressurizing the can keeps that from happening. Indeed. Tennis balls go “flat” in a short time – my memory says maybe a week or two, although I last played tennis more than a decade ago. RR ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [March 31, 2009, 3:20pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/7 "2009-03-31T15:20:28Z")
Note that pressureless tennis balls are widely available these days. (Google produces tons of links). ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [March 31, 2009, 3:33pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/8 "2009-03-31T15:33:48Z")
> [@Philster](#): > > I keep mine in hermetically sealed jars on Funk and Wagnall’s front porch. Where do you keep that big turban, though? ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 31, 2009, 4:32pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/9 "2009-03-31T16:32:33Z")
> [@Fear\_Itself](#): > > Most tennis balls are pressurized, so they can indeed go bad if the pressure leaks out. [Pressurized cans keep them fresh](http://www.itftennis.com/technical/questions/index.asp#2): Y’know, I always thought so until I read this today and thought, “Why doesn’t the top pop off from the pressure when you open it?” ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [March 31, 2009, 4:44pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/10 "2009-03-31T16:44:32Z")
> [@CookingWithGas](#): > > Y’know, I always thought so until I read this today and thought, “Why doesn’t the top pop off from the pressure when you open it?” What do you mean “pop off?” The top of a tennis ball can is, like the top of a soda pop can, a sealed metal lid, with a removable portion that has a pull ring. The plastic lid that goes over that has no pressure on it, since the sealing metal top is under it. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [March 31, 2009, 5:09pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/11 "2009-03-31T17:09:22Z")
Well whadda ya know. They _do_ spoil if exposed to the air. I did not know this. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 31, 2009, 6:42pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/12 "2009-03-31T18:42:22Z")
> [@](#): > > Note that pressureless tennis balls are widely available these days. (Google produces tons of links). Dog chew/fetch toys (which don’t need any particular pressure) are probably a bigger market than balls for actual tennis, nowadays. ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [March 31, 2009, 6:52pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/13 "2009-03-31T18:52:34Z")
I don’t understand why they can’t make them so they retain their pressure. I am assuming that the carcass is latex based, which is porous, however this problem is easily overcome by coating the inside with a minutely thin layer of butyl rubber. This is done with inner tubes for bicycles, as latex tubes improve handling quite significantly, bear in mind that I am talking about true racing equipment here, with tyres and tubes costing rather large amounts - the stuff used by pros and Category 1 amateurs. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 31, 2009, 10:23pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/14 "2009-03-31T22:23:59Z")
> [@DSYoungEsq](#): > > What do you mean “pop off?” The top of a tennis ball can is, like the top of a soda pop can, a sealed metal lid, with a removable portion that has a pull ring. I mean “pop off” like a champagne cork. I mean “pop off” like the lid of a sealed Tupperware container in the microwave. I mean “pop off” like the top of a botulism-infected can of Campbell’s. I would at least expect a big “whoosh” of air coming out. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [March 31, 2009, 10:28pm UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/15 "2009-03-31T22:28:33Z")
> [@CookingWithGas](#): > > I would at least expect a big “whoosh” of air coming out. It only has to be the same pressure as inside the ball, which is not that much. ---
**Author:** ![scm1001](https://avatars.discourse-cdn.com/v4/letter/s/c4cdca/32.png) [@scm1001](https://boards.straightdope.com/u/scm1001)\ **Post date:** [April 1, 2009, 2:38am UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/16 "2009-04-01T02:38:14Z")
> [@casdave](#): > > I don’t understand why they can’t make them so they retain their pressure. > > I am assuming that the carcass is latex based, which is porous, however this problem is easily overcome by coating the inside with a minutely thin layer of butyl rubber. > > This is done with inner tubes for bicycles, as latex tubes improve handling quite significantly, bear in mind that I am talking about true racing equipment here, with tyres and tubes costing rather large amounts - the stuff used by pros and Category 1 amateurs. A video on how they make tennis balls can be found here [Reliable Plant](http://www.reliableplant.com/article.asp?articleid=7667) The point about butyl rubber is that it must be cured and it is only about 5-8X less permeable than normal rubber so a thin layer will not do much. I am not sure that butyl rubber will stick to normal rubber so that could be another problem. The curing process requires heat and time, so that may cause problems in the manufacture. So essentially will cost more and may not provide much in that way of benefits. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [April 1, 2009, 2:44am UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/17 "2009-04-01T02:44:29Z")
FWIW, racquetballs are permeable also. Although they’re not sold under pressure, they do sell aftermarket cans you can keep them in to slightly pressurize them. I bought one when I started playing racquetball again, but didn’t use it enough to notice a difference with new balls before rugby season started. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [April 1, 2009, 5:27am UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/18 "2009-04-01T05:27:18Z")
> [@CookingWithGas](#): > > I mean “pop off” like a champagne cork. > I mean “pop off” like the lid of a sealed Tupperware container in the microwave. > I mean “pop off” like the top of a botulism-infected can of Campbell’s. > > I would at least expect a big “whoosh” of air coming out. I haven’t played tennis in years, but when I did tennis balls were sold in cans that had a key that opened them much like a tin of tuna used to. You’d crank the key around the top removing a strip of metal before you opened them. Those cans certainly did “whoosh” when the seal was broken. ---
**Author:** ![slaphead](https://avatars.discourse-cdn.com/v4/letter/s/e9bcb4/32.png) [@slaphead](https://boards.straightdope.com/u/slaphead)\ **Post date:** [April 1, 2009, 7:41am UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/19 "2009-04-01T07:41:54Z")
> [@CookingWithGas](#): > > I mean “pop off” like a champagne cork. Champagne is at about 80-90 PSI, I believe. Tennis balls are apparently at about 12. Don’t know about tupperware or rancid soup, I assume they vary somewhat. I have a vague memory of once opening a tube of tennis balls (I have never been very sporty) which had a seal somewhat like a beefed-up version of that on a pringles tube - it made a small but definite ‘pff’ when broken. ---
**Author:** ![Bluffcityguy](https://avatars.discourse-cdn.com/v4/letter/b/ebca7d/32.png) [@Bluffcityguy](https://boards.straightdope.com/u/Bluffcityguy)\ **Post date:** [April 1, 2009, 10:43am UTC](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410/20 "2009-04-01T10:43:41Z")
> [@OldGuy](#): > > I haven’t played tennis in years, but when I did tennis balls were sold in cans that had a key that opened them much like a tin of tuna used to. You’d crank the key around the top removing a strip of metal before you opened them. Those cans certainly did “whoosh” when the seal was broken. I haven’t played tennis in decades, but I remember both the key openers and the “whoosh” when you opened the cans. Cheers, bcg [Next page](https://boards.straightdope.com/t/why-are-tennis-balls-sold-in-hermetically-sealed-cans/491410.md?page=2)