What’s the purpose of the circular indentations in a gallon jug of milk?

[cainxinth]

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.

[Padeye]

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.

[Padeye]

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.

[dtilque]

Previous thread: Milk Jug Indentations

[cainxinth]

my bad, I think my searching skills need refinement

[aahala]

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.

[sj2]

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.

[handy]

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 :-)