# What’s the purpose of the circular indentations in a gallon jug of milk? **URL:** \ **Category:** Factual Questions\ **Created:** [December 6, 2002, 8:39pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011 "2002-12-06T20:39:09Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![cainxinth](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cainxinth](https://boards.straightdope.com/u/cainxinth)\ **Post date:** [December 6, 2002, 8:39pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/1 "2002-12-06T20:39:09Z")
You know, the two circular indents on the sides opposite the handle, what the heck are those things? The only thing I can think of is they have some structural purpose, like the circular windows on an airplane. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [December 6, 2002, 8:43pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/2 "2002-12-06T20:43:58Z")
Just a WAG but it may help keep the jug from bulging outward. When things made of thin, semi-rigid materials like sheet metal or plastic are made with large flat areas they tend to bulge and buckle easily. You can demonstrate this on a car with a large flat roof. Easy to press down and buckle the metal slightly but very hard to do it on a compound curve like the corner of a fender. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [December 6, 2002, 8:45pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/3 "2002-12-06T20:45:54Z")
FWIW Airplane windows are round to avoid cracks in the metal structure. Corners can form a stress riser and making a round window more evenly distributes the stress so there is no one place a crack is more likely to start. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 6, 2002, 9:24pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/4 "2002-12-06T21:24:20Z")
Previous thread: [Milk Jug Indentations](http://boards.straightdope.com/sdmb/showthread.php?&threadid=72174) ---
**Author:** ![cainxinth](https://avatars.discourse-cdn.com/v4/letter/c/7bcc69/32.png) [@cainxinth](https://boards.straightdope.com/u/cainxinth)\ **Post date:** [December 6, 2002, 10:25pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/5 "2002-12-06T22:25:17Z")
my bad, I think my searching skills need refinement ---
**Author:** ![aahala](https://avatars.discourse-cdn.com/v4/letter/a/a88e4f/32.png) [@aahala](https://boards.straightdope.com/u/aahala)\ **Post date:** [December 6, 2002, 10:28pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/6 "2002-12-06T22:28:07Z")
Dah! About two weeks ago, I wondered what might be printed under the label of the bottle of Gatorade. Hadn’t noticed till then, the bottle has a series of large figure 8 indentations. Each time I have been in a grocery or C-store, my eyes have gone to plastic bottles, water, juice etc. Every one has some series of grooves, circles or indentations. ---
**Author:** ![sj2](https://avatars.discourse-cdn.com/v4/letter/s/65b543/32.png) [@sj2](https://boards.straightdope.com/u/sj2)\ **Post date:** [December 6, 2002, 10:34pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/7 "2002-12-06T22:34:38Z")
Well, I know why they’re on apple cider. I left a half-jug of it in my fridge and left town for a few weeks. The bottle bulged all the way out. If those indents weren’t there, I may had to have moved. And they help when you drop them too, of course. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [December 6, 2002, 11:39pm UTC](https://boards.straightdope.com/t/what-s-the-purpose-of-the-circular-indentations-in-a-gallon-jug-of-milk/141011/8 "2002-12-06T23:39:10Z")
dtilque, its okay if you didn’t search, how many times would anyone expect to see a topic on milk jug indents? 🙂 If you would like to speak to someone about the Extraordinary Dairy® program, please call our Technical Support Hotline at 1-800-248-8829,. I couldn’t reach them but seems to me they would know. They have a web site [doitwithdairy.com](http://doitwithdairy.com) 🙂