Why was there a switch from 2-piece to 1-piece 2-liter bottles?

[Prox]

@Irishman

Thinking about it, smaller drink bottles, like Gatorade bottles, have a flattened bottom that still stands up better than the petaloid design. They also have a complex shape to provide reinforcement and prevent bulging, but I think something like that on a 2-L bottle would be more stable.

Probably, but Gatorade isn’t under pressure, so shard corners aren’t as big an issue with it. A lot of bottles, even glass, have an indentation on the bottom who’s sole purpose is to make the bottles look like they hold more liquid than they do. I think that has more to do with the Gatorade bottle design than pressure does.

[Irishman]

They hold 20 fl-oz, just like all the other 20 fl-oz bottles. I can’t imagine looking like they hold more plays any role. The bottles are labeled with how much they hold.

I think a large part of it has to do with reinforcing the bottom to be stiff and make a flat bottom so the bottles stand upright. Think about trying to make a flat bottom without a dimple - any imperfection is likely to make the bottom bowed out. Now make the bottom a ring with a pocket in the middle. It is inherently more stable, because the nature of the ring means there’s no central bulge. Whether contents are pressurized or not.

It’s a similar theory to the petaloid design. Rather than have one central post, there are several contact points in a ring. The grooves keep the bottom more rigid so the bottle will stand upright, the multiple contact points provide stability rather than a single “high” spot that makes it tip over.

Hey look, google found this prior conversation, where someone wrote to Ball, a company that manufactures these bottles:

Why do plastic soda bottles have those weird five-nubbed bottoms?

Kim, you might be surprised to find out that the bumps - which together
are called the “foot” of a bottle - have a number of patents and a lot
of engineering behind them. The short anser is that the foot is
designed that way for stability both during manufacture and filling, as well
as to help in shelf life and the way the bottles can be stacked for
transport.

Didn’t exactly answer the questions.

[CalMeacham]

While the two different plastics may indeed be recyclable, your recycling center may not take all plastics. Until recently, we couldn’t recycle large-mouth plastic tubs (margarine) for this very reason. Their expanded their operations so now we can recycle all plastics.

But polyethylene has always been recyclable. And both the new and the old bottles are mainly PET (which is also recyclable. Most of the Seaside Park, NJ boardwalk is now PET).

[Irishman]

As I previously mentioned, when recycling was first getting widescale attention, they limited what they accepted to clear, non-colored plastics. This may have been driven by economic issues with downstream markets for the recycled plastic rather than any recycling process issues.

[Prox]

@Irishman

I think a large part of it has to do with reinforcing the bottom to be stiff and make a flat bottom so the bottles stand upright. Think about trying to make a flat bottom without a dimple - any imperfection is likely to make the bottom bowed out. Now make the bottom a ring with a pocket in the middle. It is inherently more stable, because the nature of the ring means there’s no central bulge. Whether contents are pressurized or not.

The dimple bottom has a much sharper curve transitioning from the cylinder part of the bottle to the bottom. If the drink was under pressure, that curve would be a weak spot likely to fail. So pop has to have the more complex 5 point bottom with smoother curves.

And I can see you point about putting the dimple in a standard bottle simply to ensure there’s no convex deformation, but there are certainly bottles out there with a dimple much larger than necessary who’s only purpose is to take up space inside the bottle. When someone is trying to decide between two different drinks, they may just grab the larger bottle without checking how many ounces of liquid there is.

[CalMeacham]

As I previously mentioned, when recycling was first getting widescale attention, they limited what they accepted to clear, non-colored plastics.

This doesn’t make sense. You recycle by similar type, not appearance. There’s no point in mixing clear PET with clear HDPE – they’re different substances, and don’t mix, and require different treatment, whereas you can mingle HDPE of any color together and easily process it.

There may have been local cases of recycling only clear PET (because it was common, although at first invariably mixed with PE), but PE recycling was around first, I believe.

[TriPolar]

When we start recycling in NY in the 80s, there was a requirement to seperate by colors initially. It turned out the containers were being hand sorted anyway, and the color sorting was just a bureaucratic misunderstanding. It probably happened elsewhere. That was a long time ago though.

[Irishman]

If the aftermarket for the recycled product wants clear, non-colored stock, then it is an issue to mix the colored in with the uncolored.

I’m not saying that is the reason. I do not know the reason. I just recall the restrictions on what you were supposed to submit for recycling.

[Noel_Prosequi]

The indentation in the bottom of a champagne bottle is called a punt, and there is no apparent consensus as to why it is there. Some reasons are suggested here. No doubt they are generalisable to the present issue in large measure.

As to the two part plastic bottles, I remember a major embuggerance of them was that when you put them upright in the fridge door, the lip of the black plastic part always got stuck on the lip of the rail at the front of the door cavity as you tried to pull the bottle out. You couldn’t just whip the bottle out and get on with it; instead you had to fiddle about with two hands to release it. Annoyed me no end.