General Question

robmandu's avatar

Why are the bottoms of plastic soda bottles shaped that way?

Asked by robmandu (21306points) July 21st, 2008

They’re… um… crenellated? Here’s a picture of one from below. (nevermind they made a wind chime out of my example).

Is there a particular purpose for that shape (other than making your drink precariously perched and subject to tipping at any moment)? Is there a name for that shape?

And size of the bottle seems to matter not a whit. Small, medium, large, different brands even. If the bottle is plastic and contains soda, the bottom is shaped like that.

Plastic bottles for water, fruit juice, tea, sports drinks, etc. are not crenellated.

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11 Answers

whatthefluther's avatar

The shape makes it structurally stiffer. Without it, the bottom would be as soft and flimsy as the sides and the bottoms take most of the abuse in packaging, shipping and consumer use.

whatthefluther's avatar

Your right that juice and water bottles do not have such an extreme shape, but they do have some, let’s say, “ackward” shaping or the bottoms have thicker, stiffer plastic. Perhaps with soda, the extreme is needed because of the added pressure of carbonation.

wildflower's avatar

I suspect it’s got something to do with the carbonation and not letting the drink go flat too soon.
Basically same reason pint glasses have a slight texture in the bottom.

robmandu's avatar

Pint glasses in Ireland, maybe. Here in the U.S. we like our pint (or mug or whatever) glasses smooth, smooth, smooth on the bottom.

(Half-kidding. Dunno if we like them that way… that’s just the way they are.)

Carbonation does seem to come into play here. Now that you said that, I went to look at and whaddaya know? Perrier carbonated water bottles are also crenellated.

Hmmm… wonder what that is? More surface area on the bottom helps produce more bubbles making the beverage appear more pleasing to the eye?

wildflower's avatar

I suppose I’m a tad more focused on the pint glasses and this explains it pretty well (and it’s illustrated). Can’t find a similar thing for plastic bottles, but I’m convinced it’s the same idea (at least until someone else can point to information that suggests otherwise in a convincing way)

Harp's avatar

I’ve been looking at the patents associated with this bottom design, and nowhere do they mention any effect on the carbonation. The design is all about keeping the bottom from bowing out under the pressure of the carbonation (which would make the bottle rock on its base), minimizing the resin used in manufacture (for cost control) and preventing stress cracks in the resin (polyester is prone to these) by avoiding concentration of stresses.

stevenb's avatar

I once heard this question answered on tv. They said a lot of the above, as well as the fact that it makes the bottle look like it had more in it. Without all of those things on the bottom the bottles would be shorter and people would percieve them as a lesser bargain with less ingredients. Don’t know if it’s true. Just second hand knowledge.

Knotmyday's avatar

It gives you something to grip with the non-support hand when you’re drinking from the bottle. Delicious.

breedmitch's avatar

Does anyone remember when the, what’s it called. crenellated part had that covering around it? When they first started selling sodas in 2 liter plastic bottles there was this black outer covering over the base. Didn’t anyone else have a Cub Scout terrarium made from a cut up soda bottle?

robmandu's avatar

heh, @breedmitch…. I was thinking on this question last nite and dredged up that same old memory.

tybalt's avatar

It’s all about the structural integrity (read: strength) of the bottle and I suspect it actually offers more stability than a traditional Flat-bottomed bottle.

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