12 May 2023 Inside the existential struggle to make a perfect paper drinking straw

Designed for strength and decomposition, paper straws are full of inherent contradictions……

Paper straws have an image problem. Sentiment analysis shows that Twitter and Reddit posts on the subject are overwhelmingly negative. The same complaints echo again and again: Paper straws don’t work.

They unravel, become soggy, or just disintegrate entirely. But… It’s a straw. How hard can it be to design a sustainable single-use straw? To learn if making a satisfying straw is an impossible task, or if we simply lack the technology, we spoke to Petros Pappalas, a developer of the premium paper straws for Coasty.

Public interest (as measured by search data) in paper straws spiked in 2018 — the same year that New York City and Seattle passed laws banning single-use plastic straws. In the following years, California, Maine, Connecticut, and Vermont followed suit.

National chains like McDonald’s and Burger King also publicly committed to use more sustainable packaging. But while the commitment to paper straws is strong, they are not, and that presents a massive design problem.

The inherent contradiction

In a sense, paper straws are designed to come apart easily — that’s what being biodegradable means. The design challenge lies in creating a product that can decompose quickly in landfills or nature, but not so fast that it will start degrading on contact with a liquid, like the liquid in your glass as you try to drink it, for example.

Plastic straws work really well at getting liquid from a container into your mouth without breaking up. But they have been in production since the 1960s and take around 200 years to decompose — that means that every plastic straw that has been created still exists in a landfill or in the wild somewhere.

When straws escape the waste management system, they can wreak havoc on marine life. In 2015, tragic viral images of a sea turtle with a plastic straw embedded in its nose spurred a shift: Instead of plastic, we could use paper. (In truth, the absolute sustainable advantage of paper straws is debatable: Critics point out that paper straws are heavier than plastic straws. Shipping a heavier product requires more energy, potentially tempering some of the benefits of using environmentally-friendly materials.)

Pappalas acknowledges the frustrations of paper straw users, but he insists that better paper straws aren’t just possible — they already exist. Although many companies use the same basic method for manufacturing paper straws, he explains, slight variations in the process or the materials can cause major differences in the product.

“There are so many little steps that people wouldn’t think about, from how the paper straws are cured after they’re made [to how they’re stored],” Pappalas says. Manufacturing a better paper straw requires careful attention to detail every step of the way.

It can’t be that hard, right?

Unsurprisingly, it all starts with paper — the type of paper and its thickness play a large role in determining the strength of the straw. Popular paper choices include kraft paper, bamboo paper, and recycled paper. Some straws may also use wax paper or other coated papers. A waterproof coating improves durability, but it also renders the straw non-biodegradable, essentially defeating the point.

Kraft paper — a virgin paper made from wood pulp — creates the strongest straws. Recycled paper is considerably softer. Kraft paper has only been processed once: the wood is made into pulp which is pressed into paper. But recycled paper has been made and remade multiple times. The additional processing leads to shorter, weaker fibres when compared to newly made paper (just imagine the difference between a kettle chip and a Pringle).

Straws made from recycled paper may also contain traces of adhesive or dyes from their previous lives. These slight variations can further compromise the strength of the material.

After selecting the paper, manufacturers need to precisely dial in the weight. Pappalas explains the difficulty of this calculation.

“It’s like any recipe, where if you put too much paper in [it throws the whole thing off]. If the paper on the outer layer is too thick, it’s going to start to unravel. If it’s too thin, it’s going to get soggy,” he explains.

Paper straws can be either rolled or extruded — extruded straws are one solid piece. Unraveling is a struggle unique to rolled straws, but extruded straws are thinner and less durable.

Rolled paper straws are made using a tube winding machine, similarly to how we make the cardboard cylinder inside a roll of paper towels. Thin strips of paper run through an adhesive bath and enter a winding machine where they’re rolled around a thin metal wand. These straws have multiple layers, and are typically made from 2- or 3-ply paper.

At this stage, Pappalas emphasizes the importance of precise machine calibration, explaining that if the machine isn’t adjusted precisely for the thickness of the paper, the adhesive could be squeezed out during rolling, creating a weak seal.

To be effective, paper straws must possess two qualities: strength and water resistance. The paper selection primarily affects the strength of the straw. Some of the problems that users believe are caused by water absorption are actually caused by weak materials. A straw bending or collapsing during use is most likely a problem of strength. Add to that the fact that pressure is exerted on straws during use.

To drink through a straw, you remove the air and create a vacuum that draws the liquid up into your mouth. The vacuum generates force that draws the walls of the straw inward. Drinking a thick beverage like a milkshake requires more suction power than water or iced coffee, and applies more force to the straw. Weak products can collapse under this pressure.

Stirring a drink with a straw, chewing on it, and pinching it are all additional ways that we apply pressure. Applying force to the outside walls of the straw by stirring or pinching may cause it to bend — compromising the seal and leading to faster material breakdown.

When it comes to water resistance, the curing process is essential. Curing is the final step of paper straw construction. After they’re rolled, straws are heated and dried to thoroughly remove all of the water in the paper.

“The heating element that is used after the straws are made needs to be the right temperature and set at the right speed to draw out all the moisture so that the paper straw cures completely, and gives it a nice resilient finish,” Pappalas says.

The reason why is to do with water’s basic properties: Water molecules are attracted to other water molecules. If the paper straw is completely dry, it will form a barrier that water has to fight to penetrate. If any water remains in the paper, it creates a pathway for water to enter……

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