There’s a post I saw on reddit that points to the dimple on the side of a milk jug, and makes fun of all the people who don’t know what that’s for. In the comments are thousands of people giving dozens of different explanations, and all of them are wrong.
It is not there to indicate that the milk has spoiled by popping out due to gasses produced by spoiled milk. If there was enough gas to pop out the dimple, the whole jug would look like a balloon.
It is not there to provide structural integrity, like lateral support to prevent the bottles from crushing. The contents are under pressure, so if there was enough force on the jug from any direction, then the cap would pop off regardless of the shape in the sidewall.
The actual answer is that the dimple is added to ensure that all of the jugs contain the same volume of milk. Plastic jugs are blown into molds, and minor manufacturing variations over time would create jugs that hold different amounts of milk. Larger jugs would hold more than a gallon. They could just fill by volume, but consumers are wary of purchasing a bottle if it appears to be less full than the others. So they add the dimple to make it so that the level of milk is all the way at the top with minimal air between the milk and the cap.
You can verify this yourself by finding different jugs from the same supplier with dimples of different depths, or even no dimple at all. None of those other explanations would explain dimples of different sizes or jugs without dimples.
TLDR everybody is wrong. The milk jug dimples are added to ensure the jug contains the correct volume of milk.
I don’t think this is correct and would need to see a source before I believe it. I doubt the dimple is adjustable in the way you’re describing.
The amount of wear needed to change the volume by a noticable margin would be quite significant. Surface finish of the mold would be degraded enough that they would probably scrap the mold before using an adjustment like this as the mold would have sticking problems.
It might be volumetric compensation, but I doubt it’s directly wear related.
The mold is going to be at least two parts that split to get the blown jug out. The jug feedstock probably starts as a molded tube blank with the threads already in it. Would look like a test tube with a milk jug mouth.
Thinking about it, and I suppose you could actually call it wear compensation. Machine the mold with max dimple present. As your parting faces/lines take damage, you reface, and take some off the dimple to compensate for reduced volume. Maybe. That’s my best guess if it isn’t structual. Usually the rest of the mold has taken enough damage/wear that you’re scrapping the entire thing.
I agree with this guy, and I have to say it… username checks out.
I agree with you.
The dimple was there for stress releif:
Combined with the octagonal shape of the container, the circular, concave indent on the side of a milk container increases the stability of the plastic, allowing the internal pressure to disperse evenly. This improved structural support also allows jug manufacturers to reduce the amount of resin needed to make each container.
Read More: https://www.sciencing.com/1865028/milk-jugs-dimple-reason/
YOUR MOMS BLOWN INTO MOLDS!
These aren’t dimples, it’s the belly button. The umbilical cord was once attached to the jug at this point, after a few months of healing this is what the plastic scar tissue looks like.
The other end of the umbilical cord goes straight to the cow. After it’s cut, thats how you get cow udders!
If you jerk them the wrong way, 14 year old boys will giggle.
I would not know our milk comes in tetrapaks.
Sweden?
Nah you’re way off
I always thought it was to help prevent it exploding if dropped. I’ve dropped a gallon a couple times and the dimple pops out and the lid stays on. Kinda like an air bag.
It adds flex to the container for variations of atmospheric pressure. It’s what they mean by the fill levels.
Milk containers are filled by weight. The exact volume of the liquid can vary slightly based upon the atmospheric pressure.
If the container has no flex the top will pop off or the sides will crush in with pressure changes say when a truck drives over a mountain pass to deliver the milk.
You buy milk in gallon-sized hard plastic containers?
Is that a restaurant thing? How long does a gallon of milk last in your family?
It’s a US thing. A gallon of milk will last my family about two weeks, or less if the kids are into baking or breakfast cereal that week. I sometimes put a little milk in my coffee or tea, and I occasionally use some for making sauces or marinades. Very rarely will we throw away milk because it has spoiled, but it has happened. Maybe once a year or so, usually because of a power outage or having to travel unexpectedly.
We also have half-gallon plastic jugs which feature the same dent sometimes. When I was a kid, I remember we even had tiny pint-sized jugs for half and half, but I think that was more of a novelty.
Wait…the rest of the world doesn’t have hard jug gallons? What do they use instead?
Just to add, in Brazil we usually have 1l cartoons of UHT milk or 1l bags of pasteurized milk.
Pasteurized milk goes bad in 3 days or so, and many people can’t run through the entire 1l in that time. UHT milk will last for a good 2 weeks after opened, so I guess that’s the kind you buy.
Pretty sure it’s mostly an American thing, but I’m not well-travelled enough to be sure.
And as for rate of consumption… When I was a kid, my parents made me drink a glass of milk every day - call that 8oz, so 56oz per week. That’s a little under a half gallon (which you can also buy in plastic jugs), not including other uses like tea/coffee and cereal. Altogether, we’d go through about a gallon per week.
I bought them as the sole drinker.
Very fascinating, so much so that i don’t think it belongs in lemmy shitpost
Actually thats a lie. Its for baking a shallow pie in with the left over milk. Stop lying to everyone you bastard.
Fuck Reddit and Fuck Spez.
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Your explanation doesn’t make sense to me. The dimple is in the center of the jug, how is it related to the level of milk there?
If the jug holds slightly more than a gallon, if you squeeze the sides, it holds less.
What are you saying? Are they trying to make it hold less? Hold more? Not following.
With plastic blown molds, especially when you make millions of them, there are going to be slight variations in the sizes. If the jug is too big, they use the dimple to reduce the volume of milk you can fit inside. The bigger the jug, the deeper the dimple. If you look at many jugs at the store, they will all be roughly the same diameter but different depths. Some don’t have any dimple at all.
Ah, this makes sense now. Sorry, English is the second language and it takes some extra processing to get things sometimes. lol
The title of this post led me to believe it was about something else entirely
It’s so the sides don’t sag or bulge when full. It’s like corrugations in metal roofing/siding. Lets them get away with thinner walls.
If that were true, they would be on every jug of milk, and they would all be the same size. I have a gallon jug in my fridge right now that doesn’t have a dimple, but does have a circle where it should be.
