How the Hahtiperä shipwreck became two seamless knitted dresses with Ioncell

A wooden vessel that lay buried beneath the Finnish city of Oulu for more than 300 years has re-emerged in a way no archaeologist could have anticipated. Sections of the Hahtiperä shipwreck that could not be retained have been turned into durable fibres and used to make two seamless knitted dresses.

How did a shipwreck become a dress?

The wreck was uncovered in 2019 during construction work beneath a car park in Oulu’s former harbour area. Dating from the 17th century, the cargo ship was named Hahtiperä. Its preserved section measures roughly 20 metres long and seven metres wide, and it will be displayed at the new Tiima Museum and Science Centre.

Not all of the timber could be conserved, however. Rather than disposing of the surplus sections, maritime archaeologist Minna Koivikko of the Finnish Heritage Agency approached researchers at Aalto University. The aim was to establish whether this historic material could serve a new purpose while retaining its link to the past.

What is Ioncell technology?

The conversion was made possible by Ioncell, a technology developed by researchers at Aalto University and the University of Helsinki. The process uses an ionic liquid to dissolve the wood’s cellulose, creating a solution that is later made into filaments, yarns and fabrics, without using the carbon disulphide involved in conventional viscose manufacture.

A 2016 study published in the Textile Research Journal described Ioncell as an alternative method for producing cellulosic fibres through dry-jet wet spinning. The researchers produced both knitted and woven fabrics, showing that the yarns had properties suitable for textile applications.

How was the wood turned into fabric?

Before it was processed, decayed sections and external impurities were removed. The remaining wood was shredded and transformed into cellulose-rich pulp. According to researcher Inge Schlapp-Hackl, the shipwreck material contained few impurities and proved unexpectedly straightforward to process despite its age.

• Cleaning removed sediment and degraded areas from the timber.
• Shredding changed the historic material into cellulose pulp.
• Dissolution created a solution using the ionic liquid.
• Spinning converted regenerated cellulose into strong yarn.
• Digital knitting produced the garments without seams and with minimal waste.

The resulting yarn was soft, hard-wearing and naturally brown in colour, inherited from the wood itself. Designer Anna-Mari Leppisaari used an advanced machine and an artificial intelligence tool developed by Severi Uusitalo to create two identical dresses, made without seams and with virtually no offcuts.

Is the material truly a sustainable alternative?

Research points to promising potential, although sustainability relies on the entire process. A paper published in the journal ACS Sustainable Chemistry & Engineering in 2020 examined recovery of Ioncell’s solvent and found that recycling it is essential to reducing impacts and enabling future production at scale.

The technology has also been trialled with newspapers, used textiles, wood pulp, cotton waste and even discarded banknotes. Recent studies are exploring the repeated reuse of Ioncell fibres themselves, supporting the concept of a circular system in which cellulosic materials can re-enter the production chain instead of becoming waste.

The dress changes how we view old objects

One garment was presented in the Tomorrow’s Wardrobe exhibition at Oulu Museum of Art, while its twin was allocated to Aalto University’s Designs for a Cooler Planet exhibition. The project brings together archaeology, chemistry and design to preserve the ship’s memory without pretending that it has remained intact.

More than a fashion curiosity, the dress raises an urgent question about everything we throw away. If timber submerged for centuries can still become a sophisticated textile, much of today’s waste may also conceal new possibilities. Rethinking the value of materials now could change what ends up in museums and landfill sites in the future.