Ergonomics in Bottle Design

The term “ergonomics” is derived from two Greek words: “ergon”, meaning work, and “nomoi”, meaning natural laws. Ergonomists study human capabilities in relationship to work demands.
Today, however, the word is used to describe the science of “designing the job to fit the worker, not forcing the worker to fit the job.” Ergonomics covers all aspects of a job, from the physical stresses it places on joints, muscles, nerves, tendons, bones and the like, to environmental factors which can affect hearing, vision, and general comfort and health.

So, although in general everybody thinks that ergonomics is restricted to the work place, I like to stretch the application and implementation of ergonomics to structural packaging design. Farfetched? Not at all. A general popular definition states, that Ergonomics is defined as: “The applied science of equipment design, as for the workplace, intended to maximise productivity by reducing operator fatigue and discomfort”. Stretch the definition a bit, and you end up with: “Ergonomics is the applied science of structural packaging design, intended to maximise effectivity and consumer convenience by reducing frustration and discomfort”.

As a free-thinker you could therefore say, that ergonomics make sure that a packaging fits each consumer, and that its structural design solves physical, psychological and social aspects of the consumer in relation to a packaging.

You are still not the wiser? Well, look as an example at the consumer frustration about “openability” and “reclosability”. About which, by the way, I will write an article in the near future.

But today I like to put ergonomics into structural bottle design. When you look at the beverage bottles, and especially the larger ones, with soft drinks and fruit juices, you must agree with me that the main part isn’t designed to handle properly by whatever consumer.
Let’s take two as an example: Coca Cola and Pepsi Cola. By gauging down the thickness of the plastic material of the bottle, the 2 litre bottles can’t be handled without making a mess. Take off the cap, and the pressure in the bottle will diminish, making the walls feel and behave like a flexible packaging. The sizes of 2 litre bottles are too large already to handle with one hand. With the weak bottle walls it’s getting worse and as the consumer has to almost squeeze the walls to hold the bottle firmly, an unexpected gulp of liquid streaming out of the top is often the result, when he opens the bottle and tries to pour the soft drink into cups.

Neither Coca Cola, or Pepsi Cola, nor so many others seem to think that handling an opened bottle is part of the structural design.

Let me elaborate on this issue. It is a well-known disadvantage of plastic beverage bottles and a common daily frustration of consumers, that their propensity to being crushed when held in the hand, primarily after they are opened, causes the contents to be sprayed. This phenomenon is all the more prevalent with thin-walled bottles. And that’s exactly what causes this problem. Claiming eco-friendly factors, but without even looking at the ergonomic consequences, the current trend is to reduce the weight of bottles and thus the quantity of material of which they are composed. That is, in order to obtain a bottle of given volume and dimensions, lighter and lighter blanks, preforms or parisons, are being used today. Many a company clamours in their achievement and announces the “lightest bottle in the world”.

When the bottles are closed and they contain a non-sparkling beverage, the risk of crushing when taken in hand is nearly nil; it can, however, undergo a slight deformation that is rarely irreversible. Indeed, in this case the presence of the closing device prevents the variation of the internal volume when it is picked up. At most, a deformation of the wall at constant volume occurs.
Even when bottles with a carbonated beverage are closed, then not only the risks of crushing related to being taken in hand, but also the risks of deformation when grasped, are absolute nil. In this case the gas pressure inside the bottle exerts a force on the inner surface of the wall that resists both the variation in internal volume and the force exerted by the user to hold it.

However, when the bottle cap is removed, the risk of crushing is all the greater, because a part of the carbon pressure will release through the bottle neck and the bottle loses its rigidity. In this case the consumer tends to be less careful, because when the bottle is closed, the bottle feels very rigid.

This disadvantage has been partially remedied by making plastic bottles with reinforcing ridges on the periphery of their body. However, this solution is only somewhat satisfactory from a mechanical point of view, but often in no way from an ergonomic point of view. In other words these ridges often aren’t adding to the convenience of handling a beverage bottle.
Moreover when the ridges are to prevent appreciable deformation due to the internal pressure when the bottles are closed, they are usually not rigid enough to prevent crushing and the consumer still ends up with a bottle, which he barely can hold in one hand, while splashing its contents around.
Look at the 2 litre Coca Cola and Pepsi Cola bottles in the photos and you know what I mean.

Fortunately there are some fine bottle designs that add to the convenience of the consumer, although often even they have been designed with the mechanical aspects in mind and not the ergonomic requirements towards the consumer. To be fair I must say some designs are quite near solving the handling problem.
One of the best examples in my opinion is the plastic bottle designed and patented by Sidel in 2004 (US Patent 6695162). It is, what I like to call, the “bottle with a feminine waist”.

Let’s have a look at this design, which partly and probably unintentionally meets the ergonomic requirements for bottle design. After that, I will give some more recent examples of ergonomic designs in bottles, as some design agencies have been fortunate enough to let the laws of ergonomics enter their design skills.

The Sidel bottle with a feminine waist
From the patent we learn that the plastic bottle has a body that is cylindrical between the bottom of the bottle and the shoulder area, and is provided with reinforcing rings composed of a groove made around the body of the bottle. The groove has – from bottom to top – a lower part, a central part, and an upper part, each of these parts have a peripheral profile of a constant simple curve.

While the central part has a peripheral profile with a concavity turned toward the outside of the bottle, the upper and lower parts each have a concavity turned toward the inside of the bottle.
In point of fact, it is the combined profile of the three parts of the groove that makes is possible to provide effective protection against crushing upon opening. Additionally the structure prevents the reinforcing rings/groove from becoming deformed under the effect of internal pressure. In other words the peripheral profiles with constant curvature, mean that there are no folds or areas susceptible to creep or deformation under the effect of the internal pressure, when the bottle is closed and filled with a carbonated beverage, or under the effect of an external force when the bottle is open.

A consequence of this structural design is that some ergonomic aspects also are met, as the reinforcing rings/groove offer a grip function for the bottle, that is, the user can easily grip the bottle at the groove. For that purpose, the total height of these reinforcing rings is preferably between 60 mm and 100 mm, which allows a hand to be positioned therein.

As I said, it is one of the best (in terms of handling) plastic bottles for sparkling beverages, I have seen. Recently we have encountered some more sophisticated bottles with, obviously, ergonomics in mind.
In my next article I will show the Argentinian Arcor Corn Oil bottle designed by Tridimage, the Aguazul water bottle from Honduras, also designed by Tridimage and the water bottle for Société des Eaux d’Aix-les-Bains (SEAB) in France, developed by Sidel. I end my second article with two more ergonomic designs.