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Kornelis Caps & Closures from Steenwijk has produced 20.8 billion caps for your food over the past 90 years
When you open a jar of peanut butter, do you ever stop to think that the cap was probably made somewhere else than the jar itself? Chances are that the closure on your bottle of lemonade syrup or your coffee creamer comes from our family-owned company in Steenwijk.
Kornelis Caps & Closures is celebrating its 90th anniversary. Since its founding, approximately 20.8 billion caps and closures have rolled off its production lines, mainly for companies supplying food and beverages.
The company has been located on Eesveenseweg since the very beginning. What was once the edge of town is now almost part of the city centre. Today, its neighbours are a residential area and the railway line. Ninety years ago, there was little more than a modest row of trees surrounding the site.
Today, nearly half a billion caps and closures leave the factory every year. But according to managing director Gerben de Boer, something else is what truly makes Kornelis special. "A cap or a closure doesn’t really excite me," he admits. "Our people are the most important asset we have." To mark the anniversary, the company is publishing a book about its history, among other celebrations. An open house will be held on 24 October. De Boer, who has been in the role for 22 years, did not have to think long about the timing. "We definitely didn’t want to wait until the company turned one hundred," he says. "That has a lot to do with the fact that we still have a large group of employees who have been with us for many years."
Atmosphere
These long-serving employees can be found throughout the company—on the factory floor, in the office, and in management positions. "The fact that people stay with us for so many years says a lot about the atmosphere here," says De Boer. When energy prices soared, Kornelis helped employees finance the purchase of solar panels. And for the past twenty years, the company has been the main sponsor of the Kopje Cultuur festival in Steenwijk. De Boer explains: "You won’t sell a single extra cap because of it, but creating a pleasant place to live and work is important for our people."
Kornelis is the oldest plastics processing company in the northern Netherlands. On 16 April 1936, founder Jelte Kornelis established the business under the name Kunsthars Producten Industrie N.V. It was not until 2000 that the company adopted its current name, Kornelis Caps & Closures B.V. At the age of 70, Jelte handed over the reins to his son Wiebren, who, like his father, dedicated his entire working life to the company. To this day, members of the Kornelis family remain involved with the business from a distance.
Bicycle handlebar grips
In its early years, the company produced packaging, household items, and technical products on a small scale. These included bicycle handlebar grips, film-roll holders, and a wide range of everyday items made from Bakelite, a type of synthetic resin. Visitors heading towards the production hall today first pass a small museum showcasing historic machinery. Inside the display cases are products from those early days: the once-popular “Hoedje Wip” game, spoons, egg cups, and ointment jars.
"People sometimes ask us why we don’t make the jars ourselves," says De Boer. "But that’s a completely different market." "We stick to what we do best: caps and closures. The smallest closure we manufacture is 38 millimetres in diameter, for example for a sauce bottle or a shaker cap. The largest is 120 millimetres, such as those used for sports nutrition products." At first glance, a closure may seem like a simple product—functional, safe, and easy to use. But there is much more to it than meets the eye.
Reuse of materials
De Boer: “We do everything we can to achieve an ever-lower carbon footprint, for example by reusing materials.” “We are now fully prepared to process biobased plastics, but unfortunately the market is not yet ready for them.” Biobased plastics are made from natural, renewable resources rather than fossil-based raw materials. In November 2025, the company was awarded the EcoVadis Silver rating. EcoVadis evaluates companies on the sustainability of their business practices. De Boer: “It is an important milestone in our sustainability journey.”
Nieuwe hal
Tien jaar geleden kwam er een forse uitgebreiding: een nieuwe hal. „Tot 2040 kunnen we binnen de bestaande muren nog steeds groeien”, zegt De Boer. „En daarna is er buiten eventueel ook nog ruimte om uit te breiden.” Die groei zit ’m niet per se in het aantal medewerkers. „Instroom van personeel wordt steeds lastiger. We automatiseren en robotiseren wat we kunnen. Dan kunnen onze medewerkers zich meer richten op zaken als proces- en kwaliteitscontrole.”
Pindakaas
Hoe een product wordt verpakt en verzegeld, hangt sterk af van de samenstelling. „Neem pindakaas”, legt De Boer uit. „Daar drijft vaak een laagje olie op. Je wilt niet dat de verzegeling deels oplost door die olie. Kruiden zijn ook best lastig: je wilt de aroma’s optimaal behouden. En wat veel mensen niet weten: ook kruiden bevatten oliën.” Juist op dat soort specialistische toepassingen richt Kornelis zich. Het bedrijf is Europees marktleider op het gebied van deksels voor – inderdaad – jouw pindakaas.
Tekst: Marianne Weegenaar
Foto Gerben: Wilbert Bijzitter
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