# Which is more impermeable **URL:** \ **Category:** Factual Questions\ **Created:** [October 11, 2023, 8:23pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414 "2023-10-11T20:23:53Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 12, 2023, 3:26pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/21 "2023-10-12T15:26:13Z")
> [@thorny\_locust](#): > > They make re-usable caps for the purpose (they’ll fit any can of the size type, not just cat food cans.) I have several of them. Thanks for the suggestion - I ordered some. . I’m still wondering about the comparative values re permeability between the two… 🙂 ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [October 12, 2023, 3:30pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/22 "2023-10-12T15:30:04Z")
> [@LSLGuy](#): > > IMO the _real_ problem with aluminum foil is how you seal all the edges in an airtight fashion. Yes, it’s hard to make it airtight around the edges, where the plastic wrap is easy to seal. I think that would overcome any differences in actual permeability. > [@Lucas\_Jackson](#): > > I’m still wondering about the comparative values re permeability between the two I thought this was answered by QtM in post 3 above – aluminum foil above a certain thickness will be more impermeable (to air – much more impermeable to visible light…). ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [October 12, 2023, 3:30pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/23 "2023-10-12T15:30:12Z")
Aluminum foil is vastly less permeable, as others said. Even a thin layer on plastic film gives very low permeability. Fun facts: hot iron is permeable to carbon monoxide, and glass is permeable to helium. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 12, 2023, 3:47pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/24 "2023-10-12T15:47:37Z")
> [@Napier](#): > > and glass is permeable to helium. Isn’t everything permeable to helium? ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 12, 2023, 3:47pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/25 "2023-10-12T15:47:57Z")
> [@RitterSport](#): > > I thought this was answered by QtM in post 3 above – aluminum foil above a certain thickness will be more impermeable (to air – much more impermeable to visible light…). Right you are! Sorry QtM, somehow I overlooked that post! Apologies. ---
**Author:** ![mixdenny](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mixdenny/32/2962_2.png) [@mixdenny](https://boards.straightdope.com/u/mixdenny)\ **Post date:** [October 12, 2023, 3:59pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/26 "2023-10-12T15:59:28Z")
> [@Napier](#): > > and glass is permeable to helium. That explains the poor sales of the Corning blimp… ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [October 12, 2023, 10:50pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/27 "2023-10-12T22:50:03Z")
> [@TriPolar](#): > > Isn’t everything permeable to helium? “…austenitic stainless steel is essentially impermeable to helium…” > **[Helium permeability through austenitic stainless steel (Technical Report) |...](https://www.osti.gov/biblio/7171431)** > > The U.S. Department of Energy's Office of Scientific and Technical Information ---
**Author:** ![Al128](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/al128/32/16541_2.png) [@Al128](https://boards.straightdope.com/u/Al128)\ **Post date:** [October 13, 2023, 12:50am UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/28 "2023-10-13T00:50:45Z")
> [@Johnny\_Bravo](#): > > Is “more impermeable” correct, or is “less permeable” more accurate? Are you asking if more impermeable is less wrong then less permeable - or which of those is more right? > [@Johnny\_Bravo](#): > > > [@RitterSport](#): > > > > permeablest. > > Please don’t bring religion into this. what does that have to do with sibiria? > [@TriPolar](#): > > > [@Napier](#): > > > > and glass is permeable to helium. > > Isn’t everything permeable to helium? Chuck Norris aint … (I´ll be here all week) ---
**Author:** ![Johnny\_Bravo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_bravo/32/493_2.png) [@Johnny\_Bravo](https://boards.straightdope.com/u/Johnny_Bravo)\ **Post date:** [October 13, 2023, 1:49am UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/29 "2023-10-13T01:49:30Z")
> [@Al128](#): > > Are you asking if more impermeable is less wrong then less permeable - or which of those is more right? “Impermeable” sounds like a binary term rather than something that has degrees, so I’m wondering if asking whether something is “more impermeable” is an inaccurate turn of phrase, like saying “more invincible” or “more dead.” But “permeability” seems measurable, in that the more permeable something is, the more stuff it lets through. ---
**Author:** ![Dead\_Cat](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@Dead\_Cat](https://boards.straightdope.com/u/Dead_Cat)\ **Post date:** [October 13, 2023, 11:55am UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/30 "2023-10-13T11:55:59Z")
Scoop the remaining cat food into a small tupperware. Best seal, least waste. You may wish to have 2 or 3 containers exclusively for this, so there is always one available when the others are in the dishwasher. ---
**Author:** ![Pardel-Lux](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pardel-lux/32/20182_2.png) [@Pardel-Lux](https://boards.straightdope.com/u/Pardel-Lux)\ **Post date:** [October 13, 2023, 12:07pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/31 "2023-10-13T12:07:39Z")
Interesting username/post combination. Makes me curious too: how do dead cats eat? ---
**Author:** ![Dead\_Cat](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@Dead\_Cat](https://boards.straightdope.com/u/Dead_Cat)\ **Post date:** [October 13, 2023, 12:28pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/32 "2023-10-13T12:28:24Z")
Heh, sorry - I usually try to avoid posting in ‘pet’ threads, for this reason. But clearly the answer to your question is: they don’t, they couldn’t open the tupperware 🙂. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 13, 2023, 12:43pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/33 "2023-10-13T12:43:53Z")
Which begs the Schrödinger, is cat food in Tupperware alive or dead? ---
**Author:** ![Tibby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tibby/32/17030_2.png) [@Tibby](https://boards.straightdope.com/u/Tibby)\ **Post date:** [October 13, 2023, 12:54pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/34 "2023-10-13T12:54:29Z")
The cat food is dead, but the maggots and bacteria in spoiled cat food will be both alive and dead until you open the lid. Depending on the bacteria, you may be dead too if you eat it. Re: reusable lids. Be sure to get the proper size for your particular cans. I’ve bought “universal” silicone lids that don’t fit or properly seal any of my cans. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 13, 2023, 1:06pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/35 "2023-10-13T13:06:15Z")
Well fuck, I’ve already ordered the universal lids. ---
**Author:** ![thorny\_locust](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thorny_locust/32/431_2.png) [@thorny\_locust](https://boards.straightdope.com/u/thorny_locust)\ **Post date:** [October 13, 2023, 5:33pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/36 "2023-10-13T17:33:03Z")
> [@Tibby](#): > > I’ve bought “universal” silicone lids that don’t fit or properly seal any of my cans. IME, this varies depending on the brand; and maybe even on the batch; but probably not by whether they claim to be “universal”. After a couple of sets that were fractionally too small to get on the cans, I took to buying the ones that are out on display in groceries and pet stores – after trying them out on the cans in the store. (Without opening the cans first, of course; but there’s no need to, they’ll fit the same either way.) When I found some that did work, I bought several packs, and should now be set for quite a long time. Sorry that I didn’t warn about that before @Lucas_Jackson apparently ordered them online! Hope you’ll be lucky and they’ll work. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [October 13, 2023, 5:48pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/37 "2023-10-13T17:48:12Z")
> [@LSLGuy](#): > > For casual non-OCD wrapping, I’m going to bet you’ll have better success with plastic cling wrap. Probably, but due to changes in formulations and their effect on clinginess, I’d go with vintage cling wrap. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 13, 2023, 6:11pm UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/38 "2023-10-13T18:11:20Z")
> [@thorny\_locust](#): > > Sorry that I didn’t warn about that before @Lucas_Jackson apparently ordered them online! Hope you’ll be lucky and they’ll work. No worries, yep ordered on-line. Worst case scenario, its a few bucks. ---
**Author:** ![InternetLegend](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/internetlegend/32/13154_2.png) [@InternetLegend](https://boards.straightdope.com/u/InternetLegend)\ **Post date:** [October 14, 2023, 5:22am UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/39 "2023-10-14T05:22:02Z")
If you ordered the ones pictured earlier in the thread, they look a lot like one I have that actually does fit both the 12 oz and 5.3 oz cans (standard can sizes equivalent to the ones for canned vegetables and tuna). Nothing I’ve found fits the teensy kitten food cans. If you have trouble with a silicone lid at first, try setting it on the can and kind of wiggling it to get it sealed. I have one type of lid that I didn’t think fit at first, but with a little gentle encouragement, it was fine. The silicone lids really contain the smell well. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 14, 2023, 11:57am UTC](https://boards.straightdope.com/t/which-is-more-impermeable/991414/40 "2023-10-14T11:57:46Z")
El cheapo, but effective, way to store cat food in the can: plastic wrap sealed with a rubber band. You can reuse the plastic wrap many times, assuming you frequently empty the can and then start another. With the rubber band, you don’t have to worry about the seal of the plastic wrap. [Previous page](https://boards.straightdope.com/t/which-is-more-impermeable/991414.md?page=1)