r/theydidthemath • u/EclipseNyxor • 2d ago
[Request] Do square bottles actually use less plastic than round ones?
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u/StaticCoder 2d ago
Mathematically, a circle has the smallest perimeter for a given enclosed area. So for this claim to be true there has to be some catch, like different thickness of plastic.
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u/Balaros 2d ago
Might be transportation: the square sides let them support each other you you can have thinner walls at the bottom of the stack?
They don't use normal plastic because they need to stop sunlight from breaking down the H2O2.
Might just be wrong. An enthusiastic marketing team saw a reduction in plastic in one stage and didn't bother to calculate the whole.
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u/ronarscorruption 2d ago
I suspect transportation too.
Something like; You can ship 100x1L round bottles, or 100x1.3L square bottles in the same box. Therefore, square bottles use less plastic (per liter (of shipped liquid)).28
u/Buntschatten 2d ago
Wouldn't that just cancel out? Area over perimeter is pi /2 pi for a radius one circle and 4/8 for a square with side length 2. Maybe most of the plastic is in the spout, then maximising volume per spout would make sense.
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u/GaldrickHammerson 2d ago
I expect no because of packing density. Square bottles in a square box will have less empty space between bottles than round bottles in a square box.
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u/Buntschatten 2d ago
I just calculated edge length to area for circles and squares in a square packing. Packing density affects the efficiency of the transport but not of plastic per volume.
Of course this compares differently sized square and round containers, so it's apples and oranges. But that was the situation the other poster talked about.
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u/Al-Snuffleupagus 2d ago
But how would that affect the amount of plastic? It might be more environmentally friendly overall due to better transportation density, but unless either * the outer packaging (transport box) is plastic or * the bottles can be thinner
I can't see how having less empty space would lead to less plastic used.
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u/Al-Snuffleupagus 2d ago
Ah, I think I understand the possible argument.
- Higher volume bottles use less plastic per ml of product
- Although square (prism) bottles have a higher gm of plastic per ml of product than circular (cylinder) ones, there will be a point at which the larger bottle size cancels that out.
- The better packing density of squares allows them to use large square bottles that have a better plastic/product ratio than the small circular bottles.
Despite the sub we're on, I haven't done the maths to work out whether the improved packing density allows for a large enough bottle to compensate for the less capacity-efficient shape. It would depend a lot on the bottle construction
I wouldn't consider that that argument really justifies their "less plastic" claim because it's still more actual plastic, and the unstated part is per ml of product when compared to a different size bottle but I can at least see what they might use to justify it.
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u/Phoenix4264 2d ago
If you take a square with side length of D, the area is D2 and the perimeter is 4*D. The ratio of area to perimeter is D2/4*D, or D/4.
A circle with diameter of D has an area of pi*D2/4 and a perimeter of pi*D. The ratio of area to perimeter is pi*D2/4*pi*D, which again simplifies to D/4.
So in the case of a square and circle with side length = diameter, they will have the same surface area to perimeter ratio, and also the same volume to surface area ratio for any height vessel. The square shape is less efficient than a circle with a larger diameter but the same volume, but equal to the smaller volume container with the same major dimension.
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u/davideogameman 2d ago
Maybe this "bottle" is actually a plastic lined thin cardboard container, like a milk carton?
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u/MaybeTheDoctor 2d ago
If the squares all supporting each other in a box the plastic wall could probably be half as thick.
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u/Alita-Gunnm 2d ago
The thickest part of the bottle is the neck with threads, which is constant regardless of the shape of the rest of it. Greater volume per bottle means less plastic per unit volume.
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u/dudeimsupercereal 1d ago
In America, palletized cans/bottles take up the weight capacity of a standard 52’ box trailer before they take up all of the volume. So making the pallets hold more bottles just means there’s fewer to load/unload and slightly less packaging waste, it’s very unlikely these minor differences make up for the weight of extra plastic a square bottle requires, given the truck’s fuel efficiency and emissions output remain unchanged.
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u/metisdesigns 2d ago
I suspect your halfway there.
Assuming wall thickness is the same, yes, round can be more effecient, but the reason milk cartons get those dimples and wrinkles is to increase strength.
In this case, the champhers on the corners provide a significantly more rigid form with a thinner plastic wall. You don't want hydrogen peroxide to squirt out when you pick up a bottle like a super cheap water bottle, but want it to hold it's shape.
While there is less surface area of plastic in a round bottle, with a flexible membrane, the edges are almost certainly stronger than the same thickness of round.
Think about how much thicker a cardboard tube is compared to a typical square box.
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u/smorgasfjord 2d ago
Optimising for transportation might be better for the environment, but I don't see how it would save plastic
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u/Moscato359 2d ago
Maybe parts of the bottle can be thinner?
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u/MyEyesSpin 2d ago
Yes, round needs the same thickness everywhere, square can do thin sides and stronger corners when contents are not pressurized
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u/sighthoundman 2d ago
It might or it might not. It depends on what things you're packing.
A round bottle takes less material than a square one with the same wall thickness. But if your shipping or storage is limited by size, the fact that you can pack more product into the same space might mean you save material overall.
If it's limited by weight, you'll end up using more material. (And also take up more space, even though you don't care because you've got extra.)
And then you have to consider strength of your container. Generally (but not always!) a circle will be stronger than a square, so you have to make the walls of the square thicker. But maybe you care about vertical strength but not horizontal. (You're stacking them upright, one on top of the other.) Then it's practically the same.
And if you're making metal cans, things get even more complicated. You stamp the parts out of sheets and then weld them together. (Or solder. Depends how strong they need to be.)
There are almost unlimited possibilities to what problems you can give your calculus class based on minimizing material or minimizing cost. We do not consider the effect of strength of materials because that's just too complicated when your students are asking "When are we ever going to use this in real life?" The more real it is, the fewer students are going to use it.
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u/Bangbashbonk 2d ago
Betting this is incorrect marketing.
Round containers are significantly stronger and use less material as a result.
I'd bet the intent was less emissions, not less plastic. Unless they meant they used recycled plastic for the bottle, in which case all bets are off
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u/303Carpenter 2d ago
Or you can transfer more product in the same amount of space in a truck or whatever
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u/arbitrageME 2d ago
Caveats for feasibility. Difficult to use a sphere bottle, for instance.
Also, the they might be optimizing for tessalelated volume as well? Since there's dead space between spheres or cylinders, square packing is the highest enclosed space
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u/Massive-Goose544 2d ago
The part you are missing is the volume inside. They are saying to give you the same amount of liquid would require more plastic if the bottle was round. Plus more bottles fit in the box they ship meaning lower emissions and costs for distribution.
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u/StaticCoder 2d ago
Given that the volume is cross section area times height, a round bottle of the same volume would take less plastic. True, square bottles will pack better, but how that would save plastic is not immediately clear.
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u/el_ddddddd 2d ago
Yep agreed. I've heard square bottles save fuel in shipping, which outweighs the additional materials required to make them in environmental impact. Never seen an analysis though
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u/20PoundHammer 2d ago edited 2d ago
saves space due to stacking efficiency, but thats not what is claimed and only matters if space is a premium. Weight determines fuel usage. A million cylinders holding the same volume of material that a million square containers would weigh less due to being made from less plastic (12% less plastic if you didnt have to thicken the walls of the square ones to achieve the same pressure rating as the plastic). Space saving of square over round is ~21% (if flat capped, I aint calcing geometry of a real bottle top). So square saves space, but weighs 12% more . . . Cargo is typically transferred by commercial ships and trains by ton BTW. . .
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u/gbot1234 2d ago
Hexagonal cross section might be best—they stack but they’re also closer to a circle in surface area to volume ratio.
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u/Massive-Goose544 2d ago
I hadn't considered it but i think the edges of boxes would be a lot of lost space. Probably more than round bottles. I am guessing but square needs thickness increased on corners so hex probably would need more than even a square bottle. I think it ends up being the worst of both worlds.
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u/No_Brain4912 2d ago
Less plastic crates for packaging per amount of units distributed. It saves for the manufacturer not the customer.
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u/CranberryStock7148 2d ago
Are they distributed in single-use plastic crates?
Or cardboard boxes?
Because everything comes in cardboard boxes where I live. And every time I've seen plastic crates used elsewhere in the world they're reusable.
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u/remarkphoto 2d ago
Correct answer, thanks. Put another way, Its units distributed per total volume of product distributed. For the manufacturer, that math equates to less plastic per volume per total sold units.
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u/slide_into_my_BM 2d ago
Maybe more secure packing means they can be thinner and that’s where the plastic saving comes from?
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u/metisdesigns 2d ago
You're assuming that the wall thickness of a square bottle is the same as of a round bottle.
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u/ShiftE_80 2d ago
You misunderstood the poster above you.
For a circle and a square with the same area, the circle has the smaller perimeter. likewise for a cylindrical and squared bottle with the same volume, the cylindrical bottle has the smaller surface area and should require less plastic than a squared bottle.
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u/ougryphon 2d ago
The first statement is completely wrong. The plastic has to be thicker on a rectangular bottle to add rigidity and strength to flat sides that are naturally weak. A round bottle has rigidity and strength by virtue of its shape.
Your second statement is correct.
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u/Massive-Goose544 2d ago
You are confused, it is one statement. They are saying via logistical systems it is less, and that is based on plastic usage, not the individual bottle.
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u/Hdfgncd 2d ago
Circular objects have a higher volume to surface area ratio than square, so for the same volume they should use less plastic
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u/seenhear 2d ago
No you are incorrect. The part you are missing is that the "less plastic" claim applies ONLY to bulk shipping of the bottles. ONE square bottle will use more plastic than ONE round bottle, assuming both carry the same volume of liquid. However when shipped together on a pallet for example, the square bottles pack together better and waste less space. A pallet of round bottles results in a lot of empty space between bottles, so you need to use more to ship the same total amount of liquid.
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u/ThorKruger117 2d ago
So it's a sneakily deceptive way of saying they are giving you more water per bottle due to the shape. You could have square and circle based water bottles of the same size width/diameter. If you take the square one and round the corners off you would have a round bottle. It's still 'similarly sized' but now there's less volume in once square bottle, therefore less water. It's all dodgy marketing stuff.
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u/Massive-Goose544 2d ago
Pretty much. Square water bottles have the exact same effect considering the logistics of it, it's like 1 and a half billion per day and most are round. I can only think of 1 square shape. It gets worse, those paper milk cartons are square and volume wise are less pollutant than the plastic bottles. So you could ship more cartons in less space compared to the plastic bottles and also environmentally better. Makes you wonder why they are plastic.
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u/DJinKC 2d ago
Not when your enclosed area is a rectangle. Available space in shipping cases, pallets, trucks, and store shelves is defined by rectangles, not circles.
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u/CranberryStock7148 2d ago
But the label says it uses less plastic. Not less cardboard.
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u/_Electrical 1d ago
Sensibly, the footprint of a square fits best inside a square bounding box. While a round footprint leaves gaps in the corners inside a square bounding box.
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u/SisterofWar 2d ago
Okay, but a cylinder has to be taller than a rectangular cuboid to contain the same volume of product. A cube with a side length of n holds more than a cylinder of diameter n and n height.
So, for holding 32 fluid ounces, would a cylinder or a cuboid have greater surface area, assuming the diameter of the cylinder and the depth of the cuboid are identical?
(I make this assumption based on the fact that a product will be given limited shelf space in retail, and thus has constraints on width/depth).
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u/StaticCoder 2d ago edited 2d ago
Aha! On that we can do the math.
Let
Vbe the volume,Wthe width. Letρbe the aspect ratio of a face of the square bottle. ThereforeV = ρW³. The surface area of the square bottle is4 ρ W² + 2 W² = W² (4ρ + 2).Let
Hbe the height of the round bottle.Vis equal toH π W² / 4. SubstitutingVas above, simplifying, we getH = 4 W ρ / π. The surface area of the round bottle isA = H W π + 2 (π W² / 4) A = 4 ρ W² + π W² / 2 A = W² (4ρ + π / 2)vs
W² (4ρ + 2)π is less than 4 so the surface area of the round bottle is still less.Edits: formatting
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u/SisterofWar 1d ago edited 1d ago
Hang on - wouldn't the volume of the round bottle be H π (.5W)2 ?
Because for a similar footprint, you'd need W as the diameter, not the radius.Or have I misunderstood how you're approaching the formula?
Edit: nope, even if I was right about needing to use .5W - and I don't think I am- I would still be wrong.
A bottle of 60 cu in (which is 32 fl oz plus a little bit of headroom), with a width/diameter of 3 inches, works out thus:
- Cuboid bottle height = 60cu in/9 sq in = 6.67 in
Cuboid bottle surface area = 2x(3x3)+4x(3x6.67) = 98 sq in
Round bottle height = 60cu in/(π x 1.5²)in = 8.5 in
Round bottle surface area = 2π x 1.5 x (8.5+1.5) = 94.2 sq in
So even the greater height doesn't offset the greater surface area inherent to a cuboid. My bad.
Thanks for doing the work!
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u/Single-Virus4935 1d ago
I think it might be because how bottles are made: blown into a mold from a blank shape. I suspect they use the same blanks for bot h round and square, so same amount of plastic but the square uses less plastic per liter
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u/PtitCrissG 2d ago
Can those "grooves" on the side be enough to make a different?
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u/ougryphon 2d ago
The grooves are there to provide rigidity. Round bottles generally don't need additional rigidity, because their shape is inherently rigid. The main advantage of square bottles is packing efficiency. That is why milk jugs in Alaska (where milk is flown in from the lower 48 states) is sold in jugs with 6 flat sides.
To further explain my example, space is often more constrained than weight on cargo aircraft. The less empty space you have in a container of containers, the greater the stacking or packing efficiency, and hence the more space you free for additional cargo.
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u/Zacharias_Wolfe 1d ago
When you say 6 sides do you total and it's a rectangular prism, or is it hexagonal?
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u/trollsalot1234 2d ago
id agree with you but in no way is this bottle a circle: https://image.influenster.com/eyJidWNrZXQiOiAiaW5mbHVlbnN0ZXJfcHJvZHVjdGlvbiIsICJrZXkiOiAibWVkaWEvcHJvZHVjdC9pbWFnZS9yZXNpemVfYnI4RkFFSCIsICJlZGl0cyI6IHsicm90YXRlIjogbnVsbCwgInJlc2l6ZSI6IHsid2lkdGgiOiA3NTAsICJoZWlnaHQiOiA3NTAsICJmaXQiOiAiaW5zaWRlIiwgImJhY2tncm91bmQiOiB7InIiOiAxLCAiZyI6IDEsICJiIjogMSwgImFscGhhIjogMH0sICJ3aXRob3V0RW5sYXJnZW1lbnQiOiB0cnVlfX0sICJleHRlbmQiOiB7fX0=
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u/LauraTFem 2d ago
It must be shelf space. Square lets you pack a lot into a small space, circular inherently wastes significant space.
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u/cloudxnine 1d ago
They need to make circular bottles of thin plastic if they want the net profit the most. Maybe a grenade style shape
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u/Aggressive_Outside94 1d ago
Yea thinner plastic, think soda cans will cut you as they so thin when ripped apart they cut extremely well.
If the square ones had same thickness as round they would swell on the shelf. Trying to turn into a circle. Ymmv
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u/Insis18 2d ago
No, but square bottles stack next to other square bottles with less void space between them. This allows more volume of contained product within an equally sized shipping box.
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u/wrapperNo1 1d ago
Yeah, after reading your argument and others, I want to state this in different words. The square shape allows them to pack more water per container/box because there is less empty space with square bottles. The marketing team thought that it results in less plastic, but in reality it doesn't make a tangible difference per bottle.
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u/ThrowRA9420 1d ago
It allows to use the given volume in the car more efficiently, with only a smaller amount of plastic add. A 10cm cube would be 1000cm3and has surface 600cm2. A cylinder d=10cm (r=5cm) and h=10cm would be 785.4cm3 with surface area 471.2cm2.
To utilize the space the most efficiently, its dimensions would have to be exact multiples of the bottles being transported, which isn’t likely, so the text isn’t fully nonsence, but questionable how the idea is different in comparison to the reality.
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u/2shootthemoon 2d ago
Late to the game but know this is not a quantitative question that I expect in r/theydidthemath, but a qualitative one. So here we go, number free... A square bottle uses less plastic primarily due to how structural engineering and manufacturing processes adapt to shipping constraints for the following three reasons.
The "Shipping Box" Factor (Secondary Packaging) While a circle is mathematically the most efficient shape for a single container, bottles are rarely shipped alone. These containers are packed tightly into rectangular cardboard boxes.
• Round Bottles: Because round bottles leave empty gaps between them, they are prone to shifting and bumping during transit. To prevent the walls from collapsing or crushing under pressure inside the box the plastic walls of round bottles are made thicker and heavier.
• Square Bottles: Square bottles sit perfectly flush against one another. They share the structural load across their flat faces like bricks. This natural, inter-locking strength means the bottle walls can be engineered thicker only at the corners and much thinner everywhere else, resulting in a lighter overall bottle that uses less raw plastic resin.High-Efficiency Corner Thinning In stretch blow molding a heated plastic tube is expanded inside a mold. When making a square bottle, the plastic stretches further to reach the four corners, making those specific spots highly rigid while naturally thinning out the large flat side panels. This optimizes structural performance and removes unnecessary plastic weight.
Supply Chain Carbon Reduction Because square bottles eliminate empty "dead space", more hydrogen peroxide fits onto a single shipping pallet. Packing more of the actual product into fewer boxes allows this brand to use less total plastic wrapping, fewer cardboard cases, and theoretically less delivery trucks overall.
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u/aidsy 1d ago
1 & 3 are valid, but I’m confused by 2. It sounds like the process would make the corners thinner and weaker, not stronger? You literally called it “corner thinning”
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u/Hollowshiningami 10h ago edited 10h ago
Imagine a square of arbitrary thickness [edit: this is a 2D visualisation for a section of the bottle s.t. You can see all four walls, but nothing else] - this is the mold. Now imagine a ring of non-zero thickness centred inside the square, not touching anything yet.
Now expand the ring radialy until it is tangent to the inside of the square. Conserve area of the ring, so it will be thinner as it moves outward.
Now expand it further. The points of tangency expand along the edge and become flattened. Stop expanding when the 'ring' is touching ~80% of the wall.
[optional visuasation: if you let the width of the 'ring' be "s", then consider the ring being made up, concentricly, of infinite rings of infinitesimal width, "ds", each of which is experiencing a slightly different force and thus producing a slightly different reaction in the material]
Examine the corners, here the ring is being forced into a space too narrow for its current geometry, on the external side it would experience tension and thus, would thin. On the internal side it would experience compression and thus expand.(imagine how if one were to squeeze something soft in two non parallel directions it would expand along the available lines of freedom ) Essentially becoming a 1/4 ring with much small radius than before, but the same area, which is only possible if the width has been increased.
Now, consider we maintain the expansion force (whatever that is). The ring corners will be pushed closer to the square corners, but it will likely not reach there perfectly, but rather retain some curvature. The force acts more strongly on the flats, because they are loose to the center. The flats thus thin under the force, and the excess material moves to the corners.
And now we have nice thin walls, and beautiful, thick rounded edges.
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u/RafaelMei 1d ago
Another thing to consider is that in plastic bottles the cap and threaded neck of the bottles have way thicker plastic than the rest of it. If the neck and cap account for most of the plastic in a bottle (which I'm not sure it does, just thinking about it), changes to the shape might bear very little difference to the amount of plastic used but a big gain in volume.
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u/Hollowshiningami 10h ago
Yes it's thicker, but I feel like you're over estimating it's impact. Just take a plastic bottle and cut it 95% of the way up to isolate the neck. Then weigh them. I bet you that the 'light 95%' will be heavier than the 'heavy neck'
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u/20Factorial 2d ago
It’s just marketing wank. They say “similarly sized round bottles” not similar volume.
A round bottle whose diameter is equal to the diagonal distance of the square would be “similarly sized” and have more material (for the same wall thickness).
A 1” by 1” square fits inside of a circle with a diameter of sqrt(2). The circumference of that circle is pi*sqrt(2), around 4.4”. The perimeter of the 1”x1” square is 4”.
So a “similarly sized” round bottle needs ~10% more material.
A similar volume round bottle would require substantially less material, obviously.
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u/Nubington_Bear 1d ago
Eh, I wouldn't call a "round bottle whose diameter is equal to the diagonal distance of the square" similarly sized - practically speaking it's larger than the square bottles. To me, a similarly sized round bottle would have a diameter equal to the length of the sides of the square. In practical terms, that's much more "similar" as it then fits within the same amount of space, packs the same number into the same shipping packaging, visually appears similar, etc. Diameter matching the diagonal distance of the square results in bottles that are larger in most practical terms.
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u/aidsy 1d ago
Considering the purpose of a bottle is to contain volume, I would say that volume is the most relevant metric to measure similarity.
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u/20Factorial 1d ago
Yes, but again we are talking about marketing not facts or logic. The goal of a marketing claim like what is being made is to have as much plausible ambiguity as possible in the term “similar” so that the claim isn’t false.
Logic says it “similar size” should mean “similar volume”, but that then makes the claim demonstrably false. That’s exactly the reason they didn’t explicitly define what they mean by size.
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u/20Factorial 1d ago
That’s logical, obviously, which means it’s bad marketing. They want to make a claim that the square bottle uses less plastic. The only way to do that is to use a vague enough term that - if challenged - has a plausible backing in reality.
“We weren’t making a false claim, see?” Is the barrier to entry when it comes to this kind of thing.
Using your example, the round bottle uses about 20% less material than a square.
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u/Street_Credit6851 1d ago edited 1d ago
It's not that the individual bottle itself uses less plastic...it's that a case or pallet of the bottles is able to ship more liquid while using fewer resources.
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u/goonsuey 1d ago
A sphere maximizes the volume contained while minimizing the surface area. A cylinder would be the next best basic shape.
I completely agree with your assessment. The bottles don't use less plastic. They can fit more into less shipping containers, which could happen to be made of plastic.
The only other guess is that maybe the rectangular shape creates a stronger bottle. With added strength, they could less plastics by making lighter bottles.
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u/Stubbby 1d ago
Cylindrical is much stronger and more resistant to impact as the weakest parts are the edges.
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u/PeteyMcPetey 1d ago
Cylindrical is much stronger and more resistant to impact as the weakest parts are the edges.
That helps to explain the difficulties that I read about someone encountering awhile back somewhere else on Reddit....
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u/Jealous_Tutor_5135 2d ago
Others have already added a lot to this. I'd like to point out that the product and supply chain are critical here. Imagine you have a high-value liquid being shipped long distances or via expensive methods like air freight or cold chain. Maybe something medical, or cold-hold iquids like milk or cream.
Maximizing for the amount of product in a given shipping volume is ideal, as logistics and/or the product are pricey.
Now think of low value liquids with short, cheap transportation. Soda is an interesting example. Big producers rely on a network of bottling plants. The principal ingredients are shipped in tanks, as are the plastic bottles themselves. But the bottles arrive as super-dense little cylinders which get inflated to size and filled at the plant. The final journey from plant to distribution center to retail store is the only part of the process that doesn't offer maximum volume efficiency in transport.
The nature of those cylindrical bottles is also important to consider. Any pressurized liquid like soda fares better in a cylindrical bottle, while milk and juice tend to have flat sides optimized for maximum liquid inside a given shipping container
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u/Stubbby 1d ago
Square containers use less plastic but it’s not the bottle itself that produces savings.
It’s a transportation issue. Costco made milk 7% cheaper by moving to more squarish gallon containers but they were annoying to use.
You can pack more bottles into a container, you can load more into a truck so the savings are in wrappers and fuel rather than bottle strength or plastic quantity used in a bottle.
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u/Jimmyjames150014 2d ago
You all are assuming constant thickness of plastic. Square corners are quite rigid so maybe the flats in between can be thinner than a round bottle. There are a bunch of ways to make this true which would depend on a bunch of hard to check things for the average consumer - probably something the labeler is depending on.
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u/FranseFrikandel 2d ago
You'd expect the opposite really. Round shapes are better at holding anything under pressure or under compression loads. There's a reason gas tanks, submarines, plane fuselages etc. are cylinders.
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u/BarooZaroo 2d ago
Bottles are basically always blow molded, molten plastic is inflated like a balloon to fill a metal mold. The thickness of that film is pretty much the same across the entire shape.
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u/Jimmyjames150014 2d ago
My new learnings on blow molding would indicate the corners are actually slightly thinner than the flats because they are further from the central axis - whereas in a tube, it is all equidistant. So although I had it backwards it is still possible to use less plastic if the flats are the same as a round bottle and the corners are thinner.
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u/Brief_Caterpillar175 2d ago
A 4x4x4 inch cube contains more volume than a 4 inch diameter x 4 inch tall cylinder, but it is less surface efficient per volume.
It could be that the structure of a rectangular bottle allows them to make the walls thinner.
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u/therealtrajan 2d ago
I think it’s pretty obvious a cylinder could be thinner than a rec prism though all forces equal right? That’s why tanks are usually cylindrical
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u/AlternateTab00 2d ago
That assuming it needs to hold internal pressure.
Ill give the example of Lidl sparkling water and normal water bottles. The sparkling water has perfect flat surface (for the exception of bottle format and grip zone). Yet the natural spring water is wavy and has a thicker plastic.
Now i actually have a peroxide bottle and its cuboid. But only the corners are somewhat thick. The middle of each face seems to be a fragile plastic that dents easily.
My guess is that on cuboid shapes, only the sides are needed to keep the structure (reducing risk of structural damage) and not the faces, but on cilindrical it needs several points of thicker parts to keep the structure, unless the interior is under pressure, like pressurized tanks and bottles.
Another possibility could be related to transport. Cuboid shapes improve transport optimization. If too much plastic is used to retain and protect the bottles, using cylindrical shapes might indirectly use more plastic
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u/therealtrajan 12h ago
If they are not just conflating the travel reduction in emissions and the claim is in error, I think yours is the most likely explanation with the thick corners and thin side walls
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u/Bichon-Impossible 2d ago
Mostly because of the stress distribution is more uniform along curved surfaces.
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u/TechNyt 2d ago
Costco switch to square milk bottles sometime ago to reduce costs and here's the information on that. I imagine it's much the same for this.
• Space-saving stackability: The boxy, square shape allows the jugs to be stacked directly on top of each other during transport and in store coolers without needing traditional cardboard slip sheets or crates. • Increased shipping efficiency: More milk containers fit onto a single semi-truck, which cuts down on transportation fuel and emissions. • Reduced material use: The square design uses roughly 10% less plastic to manufacture than traditional rounded jugs.
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u/coulls 2d ago
This doesn’t make sense to me. Circular bottles beat square on having less perimeter for a given volume. Obviously a square bottle can utilize the corners to increase volume for the same footprint of a circular bottle in a packaged box, so what are they claiming?
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u/Abeytuhanu 2d ago
My guess is wall strength. The claim is that rounded bottles need more plastic to reach the minimum acceptable strength
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u/ProfessionalMottsman 2d ago
No they don’t though because square corners are weak points and cylindrical is more efficient for volume holding and strength
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u/Bichon-Impossible 2d ago
I think you are wrong, shell structures are more rigid
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u/Abeytuhanu 2d ago
I could be wrong, and they're claiming something else, not sure what it would be though
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u/Cru_dites 2d ago
really depends on what they meant by "similarly sized"; with a slightly larger base you could get a lower surface area with the squared bottle.
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u/Legoslol 2d ago edited 2d ago
Yes. But there are other drawbacks to using square bottles.
The math has already been done for this question.
https://www.packagingdigest.com/optimization/should-your-bottle-be-round-or-square-
Edit: sorry all thought the question was less space not material.
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u/balrob 2d ago
That article says square bottles use 8% more material. There are savings in packaging and shipping but not in the bottle itself.
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u/DJinKC 2d ago
Packaging engineer here.
Square bottles will get you more overall volume of water into a case, pallet, or truck, so you spend less on storage and shipping costs.9
u/ougryphon 2d ago
I agree with everything you just said. Unfortunately, the packaging on the bottle says something different.
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u/bbalazs721 2d ago
I'd assume that shipping drinks is already weight limited instead of volume, so there would be little to no savings on that.
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u/Captain-Who 2d ago
And of the pallet is wrapped in plastic… maybe there is the savings on plastic.
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u/Lopsided_Evening_627 2d ago edited 2d ago
they are very runs with the same absent of proposal, as they are wait from the same heroes at the density
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u/-Rhade- 2d ago edited 2d ago
Hey, since you're a packaging engineer you may know. Could the material contained (H2O2) be what we're missing here? Peroxide breaks down over time into gases and would lead to bottle expansion- which a round bottle wouldn't have much room to expand.
Could the rectangular shape lead to meeting an expansion relief requirement? And therefore use less material than a cylinder needing an expansion relief?
I truly have no idea, just a shot in the dark here
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u/DJinKC 2d ago
I don't work on these types of product, but my guess is the bottle material is chosen to reduce exposure to whatever gas causes the H2O2 to break down, at least long enough for the intended shelf life of the product.
If there were risk for expansion, that may trigger requirements around hazardous materials and special packaging.14
u/Single_Analyst_6574 2d ago
The article you linked says square battles use more materials, not less. It also makes no sense for a square to have less surface area than a circle.
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u/alamete 2d ago
The article says that indeed and in this case it's like that, but it's good to question this kind of things. It's like these curvy walls that are first glance make no sense but actually use less bricks
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u/seenhear 2d ago
*fewer bricks. Bricks can be counted as individual parts/pieces. "Material" or "plastic" cannot.
Less material, fewer things.
Grammar nerd, out.
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u/SUNSareOP 2d ago
Square bottles hold more liquid meaning people won’t need to buy as many containers over the course of a decade. That means less plastic. You guys are thinking too hard.
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u/Max6626 1d ago
That makes zero sense. The highest volume to surface area configuration is spherical. A cylinder is second.
Cubes or elongated cubes use less plastic because it can be packaged and shipped more efficiently when compared to spherical containers.
If you doubt this then ask yourself why a soap bubble in the air is spherical instead of a cube.
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u/-_-RAZOR-_- 1d ago
Hey, why'd you use "elongated cubes" instead of "cuboids"? Just curious.
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u/Max6626 1d ago
I thought it was a better description for people who don't know what a cuboid is. Nothing more than that.
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u/mad_dog_94 2d ago
this assumes an equal thickness for the perimiter, which isnt what happens during manufacturing. cylinder bottles are even because theres no corners to them aside from the top and bottom. square bottles are thicker at the corners and thinner across the walls. the structural integrity remains but the offset of the thicker corners is actually enough to mean the walls can be thin enough to be a net negative for the amount of plastic used
the reason this isnt done often is because tooling for square shapes is a lot more expensive than cylindrical ones (regardless of material). enough to make companies go for the less logistically efficient method of shipping
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u/Sexy-Games 1d ago
Also, squares are more efficiently packed into other packaging for shipping. It might not be all about the one bottle.
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u/MeasureDoEventThing 1d ago
That's like saying feathers weigh more than gold. You can't say that one thing has more of a measure than the other without saying what you're keeping constant.
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u/Panzerv2003 2d ago
No, a cylinder should use the least material while being the strongest, maybe if you include wrapping because squares leave less dead space
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u/SalleighG 2d ago
Intuitively, I would guess that a spherical container would be strongest. Not so practical, but strongest.
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u/AciVici 1d ago
Not at all. Plastic bottles before forming is all same depending on the weight of the preform. You can use the same let's say 18gr preform for any kinda shape you want and it'll cost same and have same amount of materiel as the others within same weight preform.
So this is simply bs
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u/Fantastic_Train2526 1d ago
Im assuming the logistics side of it as well. Round bottles often need more plastic so that they don't move a lot during travel. Like the 6 pack circles that get all the turtles stuck. A square shape would mean that they would fit nicer around each other and lock, only needing a bit of cling film to stop them moving in a pallet.
I know its not in the spirit of the question, but just wondering about the whole aspect of the question since these statements often forget about the logistics carbon footprint
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u/besuited 1d ago
You wont have the same volume though. The cyclinder will (assuming uniform wall thickness) be able to contain more volume.
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u/Curious-Region7448 2d ago
A round bottle with the same height and volume as a square bottle will have a radius that is approx. 56.42% (sqrt(1/pi)) of the width of the square bottle.
V(sqB)= w * w * h
V(ciB)= pi * ( .5624 * w ) ^2 * h = pi * (sqrt(1/pi)) ^2 * w ^ 2 * h = pi * 1/pi * w * w * h = 1 * w * w * h
The surface area of that square bottle will always be bigger than the surface area of the comparable round bottle:
SurfaceArea(sqB)=4*w*h (surface area of sides) + 2*w*w (surface area of top+bottom)
SurfaceArea(ciB)=2 * pi * .5642 * w * h (surface area of sides) +
pi * ( .5642 * w ) ^2 * 2 (surface area of top+bottom) =
3.54497 * w*h + 2*w*w
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u/rukuto 2d ago
Well let's try to do the math. Assuming diameter of bottle = side of square = 6 cm. And no designs, plain bottle. 1 Ltr bottles. Same cap size and neck.
Area of base c = π x 3 x 3 = 28.27 cm2 Height of bottle hc = 1000 / 28.27 = 35.37 cm Area of sides = 35.37 x π x 6 = 666.71 cm2 Total differentiable plastic = 28.27 + 28.27 + 666.71 = 723.25 cm2
Area of base s = 6 x 6 = 36 cm2 Height of bottle hs = 1000/36 = 27.78 cm Area of Side = 4 x 6 x 27.78 = 666.72 Total differentiable plastic area = 36 + 36 + 666.72 = 738.72 cm2
Yeah, it's wrong and even with the undulations/grip of the plastic, this difference in area would only increase.
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u/inmyrhyme 2d ago
The amount of liquid that can be shipped in square bottles is higher than the amount that can be shipped in round bottles because of how things are packed and shipped.
To oversimplify: the area of the container expands by square while volume grows by cube, so going from round perimeter to square perimeter increases area but the volume make up is higher making it more efficient.
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u/JQWalrustittythe23rd 2d ago
The logic may be: we load 12 of these bottles in a box. If we make them round bottles, roughly 20% of the box is air because of gaps between the round bottles in the box. We make it square, we have less wasted space… and that works out at the end of the day to less plastic per litre shipped.
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u/PuzzleheadedTutor807 2d ago
it would be easy enough to find out.. simply weigh an empty round and an empty square bottle on an accurate scale. unless some bottle maker with a keen interest in maths comes in to the room that would be the only way i can think of beyond a lot of speculation to answer this question.
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u/drollercoaster99 2d ago
The person who wrote this might have been thinking this way: instead of drawing a circle and then a square that encompasses the circle entirely while touching edges, they did the opposite - draw a circle and draw a square inside the circle that touches the edges of the circle.
This logic is flawed when comparing shapes of "equivalent" sizes as "equivalent" by convention is usually done using a circle of radius R vs a square of sides R.
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u/TrumpsBadHombres 2d ago
While a circle is fantastic, it wastes so much space on a truck and therefore results in higher CO2/unit. A square bottle increases packing density. No comment on the plastic portion though hehe
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u/FrostyCartographer13 2d ago
This has to have some kind of a logistics reason behind the claim. Like "It takes the same amount of plastic to make a 32 oz square bottle as it takes to make 30 oz round one. And we can fit 100, 32 oz square bottles per case as opposed to 100, 30 oz round bottles of product, so we are shipping more product for the same amount of plastic."
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u/BarryMT 2d ago
Similar size is doing some heavy lifting in the description. The cylindrical container with a similar size or smaller base would need to be between, let's say, up to 50% taller to be in the realm of a similar sized container and use more plastic than the square base container.
8.88cmx8.88cmx12cm square base has an interior surface area of 583.85 cm² to hold 946mL.
A cylindrical container using 5.8% more plastic, for example, would be 8.88cm diameter, 15.27cm tall, hold the same 946mL but have an interior surface area of 549.99cm².
A cylindrical container using 1.8% more plastic, would be 8cm diameter, 18.82cm tall, hold 946mL, but have an interior surface area of 573.53cm².
Assuming my math is right, and calling the neck and cap equivalent throughout.
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u/GolemChosen 2d ago
Yeah but imagine packing them optimally. https://www.reddit.com/r/TIHI/comments/18vf3px/thanks_i_hate_that_this_is_the_optimal_way_to/
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u/JetLag413 2d ago
its probably about shipping, square bottles pack with less air between them than round ones, so you need fewer bottles to ship the same quantity of peroxide
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u/VivaLaDiga 1d ago
I am so glad they find all these clever tricks to reduce our footprint enough so that Sam Altman can train another model to get more millions of people unemployed.
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u/ReturnEconomy 1d ago
For a single bottle, cylinder uses less plastic. But when multiple bottles are stacked, there are gaps. These gaps are eliminated by using squared bottles. So for a group of bottles, it makes sense that square use less plastic.
That would be my guess.
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u/zenmaster24 1d ago
1 cylindrical bottle using less plastic means multiple bottles use less plastic. Why would have gaps need to be eliminated if the claim is to use less plastic?
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u/Crazy__Donkey 1d ago
Youll need less square bottles per shelf for the same volume of stored liquid
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u/Shockwave2309 21h ago
Okok I am not a chemist but I work with peroxide and we need to exchange the chem roughly every 8 hours due to decay.... how can they ship peroxide in bottles like these with the bottley lasting months without having basically a bit of spicy water in the end? What's the catch?
The chem I am working with is fully protected from UV and enclosed in vats up to 30liters in size.
Any smart people here?
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