Right versus light

Lighter, but more stable; fewer resources, but higher performance: packaging manufacturers are increasingly confronted with demands like these. As a natural raw material that is infinitely recyclable, there’s no doubt that glass offers clear advantages over other materials when it comes to sustainability. But like every other sector, the glass industry is aiming to improve resource efficiency – so manufacturers are searching for more ways to reduce material usage without compromising the performance of glass packaging. 

Here at Vetropack, Dennis Gsell grapples with this challenge on a daily basis. He belongs to a project group established in mid-2024, dedicated to the concept of ‘rightweighting’. This term is frequently used in the glass packaging industry, often in conjunction with ‘lightweighting’. But what does it actually mean, and how do the two terms differ? “

Lightweighting is mainly about reducing the weight of glass packaging,” says Gsell. “As you’d expect, stability and consumer safety are key factors here. Rightweighting, however, is a more comprehensive approach. The goal here is to determine the optimum weight for a glass container so that it can still deliver the required performance. With rightweighting, we address all requirements for the value chain – including aesthetics, branding, product protection, performance criteria such as strength and quality, fillers’ requirements, technical feasibility, and environmental considerations.” Once all these factors are taken into account, the ratio of weight to performance has to be right.

Fit for purpose

‘Fit for purpose’ is the guiding principle for rightweighting. The aim: to strike the right balance between material usage, functionality, and stability. On the one hand, individual glass containers must not be too heavy or oversized – otherwise material would be wasted. But on the other, a container must not be undersized because that would make it too fragile – and both product integrity and consumer safety could be compromised. So in some cases, rightweighting may actually mean making the glass packaging heavier to enhance its overall performance. 

Rightweighting is a challenging process, and it requires an in-depth analysis of product requirements including life cycle, handling, and conditions of use. Gsell illustrates the technical complexities of material reduction using a gherkin jar as an example: most of its weight is concentrated in the finish (or mouth), where regulatory requirements apply.

The jar’s finish must be strong enough to withstand vacuum pressure and accommodate screw caps. The shoulder area also offers potential for optimisation: the transition from the body to the neck is sometimes thicker than necessary. A smoother contour in this region can save material without increasing the risk of breakage. 

But it is the base of the jar that accounts for most of its total weight. A shape that is slightly concave (curved inwardly) provides stability without requiring excessive material. As a final factor, technical experts examine how far the wall thickness can be optimised. Modern glass formulations offer increased strength to allow thinner walls. Glass technicians make use of various indicators to evaluate progress in rightweighting. One key parameter is the ‘alpha index’, which reflects the ratio between the container’s volume and the weight required to achieve a given capacity.

Leading the beer market

Dennis Gsell points out that three different factors are driving rightweighting ahead at present. The first is sustainability – which focuses particularly on each container’s energy footprint. Second comes cost: less material per unit means money saved. And the third factor is innovation. “We keep a very close watch on the market, of course, and we monitor our portfolio to identify potential for improvements. But at Vetropack, we don’t merely aim to follow the market. In line with our corporate strategy, we ourselves want to set standards for making glass more sustainable and efficient.” The EU Packaging and Packaging Waste Regulation (PPWR) includes a requirement to minimise packaging, and this is an added incentive for us to challenge technical limitations and explore alternative solutions. 

Gsell believes Vetropack holds a leading position in both the beer and milk bottle segments. Perhaps the bestknown innovation in recent years is Vetropack’s thermally tempered lightweight glass bottle: as a 0.33-litre reusable container, it weighs 30 percent less than a standard bottle – with significantly less scuffing. So this lightweighting project has succeeded in improving performance as well as reducing weight. In the food sector, too, substantial weight reductions have been achieved: one outstanding example is Vetropack’s collaboration with J.C. Fridlin Gewürze AG, the Swiss spice specialist. This partnership has led to the redesign of existing spice jars and the introduction of a new lightweight glass jar. The benefits: annual savings of around
190 metric tons of glass, more efficient palletising, and lower CO₂ in the logistics process. And in the wine sector, the project group is currently testing various bottles including an ultra-lightweight Burgundy bottle.

“We approach customers proactively”

So what are the priorities for this relatively new project group at Vetropack? Right now, the team is setting its goals for the current year. “We believe it’s important to approach our customers proactively and offer them suggestions,” says Gsell, highlighting the group’s customer-oriented approach. The group is diverse enough to include all possible perspectives: alongside four members from the Performance team, there are representatives from Marketing, Sales, and Sustainability. The full interdisciplinary team meets at least once each quarter and at present, they are working simultaneously on two projects. 

The main challenges going forward are in the processes, Gsell believes. If less material is to be used per unit, production of the lighter glass containers must ensure that utilisation of melting capacity is maintained at the same level. Stable production processes are essential for manufacturing lighter items at higher speeds, and strict quality control measures will continue to be an absolute must. To sum up: given the right balance, brand owners can reduce costs by improving material efficiency with no compromises on consumer safety; and at the same time, they can guarantee high product standards while achieving significant sustainability advantages and gaining competitive edge.