I figure everything in industrial design had some mathematical or physical logic to it, but i can’t understand the advantage of a bottom that protrudes inwards. Thanks!
I figure everything in industrial design had some mathematical or physical logic to it, but i can’t understand the advantage of a bottom that protrudes inwards. Thanks!
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It is called the punt and it has several reasons, but most of them are outdated and kept mostly for tradition.
In old glassblowing techniques it helped to make sure the bottle would stand upright, as it was hard to make a smooth bottom. It also helps the structural integrity of a bottle that is holding pressurized liquid like champaign as rough flat surfaces are more likely to break.
Why do we put domed roofs on old buildings?
It distributes the load of the pressure better.
Sharp angles (like a flat bottomed cylinder would have) create stress points for internal forces.
The dome is concaved inward so it doesn’t sit wonky the concave itself distributes load better when stacking bottles and the like.
Make a tall object with a convex bottom. Try to make it stand up. And you will quickly realise the problem. It becomes unstable.
Flat bottoms solves some of the problem, but requires a flat surface to be stable. Not all surfaces in real life are flat. You can add a flange at the bottom of the bottle, but then you have to create a much more complex shape, which is harder than just pushing in the bottom of the container a bit.
Also, a side benefit of making a concave bottom is that it consumes some of the volume of the container, making it look larger for the same volume. Which is a benefit if you are trying to sell the content of the bottle.
It’s the the same reason many roofs are domed: arches and domes are stronger in supporting a load. They transform sheering/lateral forces into compressive forces. Bottles can need to survive a surprising amount of force, not necessarily from pressure of the contents but when being transported. When being bumped and jostled they can be subject to a “water hammer” effect which can blow the bottom off from the momentum of the liquid slamming into the bottom. Having a dome on the bottom is when efficient way to reinforce it without adding too much more material.
Some of the other reasons posted here are also correct, but sometimes the concave bottom is there to mitigate the amount of foam generated during the filling process so that bottles can be filled more quickly on the filling line.
Wine bottles sometimes show pretty extreme examples of this and some buyers seem to think it is to fool them about the amount of wine in the bottle. Really it is there to minimize splashing and thus the amount of oxygen introduced during the filling process to better preserve the wine.
Have you ever tried holding a piece of paper flat from one end? It droops, unsurprisingly. But if you press down in the middle to bend it in an arch on one side, it suddenly is able to stay upright even when held from one side. That arch gives a lot more strength to the shape.
Then extrapolate that to a circle, and you’ve got the shape they use in bottles- it’s much stronger than flat glass.
I do pottery. A “foot ring” on the bottom lets you place the container on a surface that is not perfectly level or even. A flat base requires that the surface not have any bumps or abnormalities. Of course a convex surface won’t work. Ever try to stand an egg on it’s end? It’s not easy to do. Depending on the container and it’s use, a concave base on a container that seals will also hold up better to internal pressure.
It’s a combination of the shape being more stable when on a table, being easier to produce reliably (a flat bottom needs to be exact or it will wobble), reduces volume of container, place for finger for up market waiters to pour, tradition
Strength. Curved surfaces tend to resist forces better than flat ones, just look at arches and domes. They have been used throughout history to support the maximum amount of weight with the least amount of material.
Having a flat bottom means that the middle of that surface is especially susceptible to forces that might occur when you put the bottle down. Adding a positive curve would put a point that would bear all the stress, adding a negative curve makes a larger contact ring which spread out the stresses.
It also protects against internal forces, as well as external ones. If the bottle is pressurized or holds a lot of weight then a curve is going to hold that pressure better than a flat surface.
There are other ways to accomplish such things but a concave bottom solves a lot of problems with a minimal amount of material and without extra manufacturing to make the bottle.
The punt in a wine bottle is a legacy of hand blown bottles. Rather than try to make a flat surface, it was easier to push it in and make a ringed surface. The early glass molds were similar, in that the manufacturing made it easier to have a ringed surface rather than a flat surface. The bottle was more stable if it was not flat at the bottom. Technology was not always as precise as it is today.
Beyond that there is no purpose to a punt. . A wine bottle with a very deep punt is often used for more expensive wine, because it looks more dramatic. As far as collecting sediment, etc, no design was made with that as the primary purpose. That’s just something that might be useful, and like many things regarding wine, has all sorts of myth attached to it.