Resortecs, the sewing thread that melts when heated

The seam ripper is one of the most humble tools in a workshop: a fork-shaped blade and a plastic handle. Yet, when it comes to separating the components of an end-of-life product, it still does most of the work. Stitch by stitch, by hand, with time and costs that often make dismantling more expensive than the material being recovered.

Resortecs, a Brussels-based start-up led by co-founder and CEO Cédric Vanhoeck, has chosen to turn the problem on its head: rather than inventing a better way to cut seams, it has designed a seam that comes undone by itself. The system consists of two parts. The first is called Smart Stitch: a range of 16 sewing threads, both synthetic and bio-based, which dissolve when heated to 170 or 190 °C, depending on the application. The second, Smart Disassembly, comprises the machines and thermal tools that apply this heat. The disassembly plant operates in a low-oxygen chamber to prevent the fabrics from oxidising, and enables up to 90 per cent of a textile product to be recovered for recycling, compared with an average of 50 per cent with manual or mechanical disassembly. A pilot line in Brazil currently processes between half a tonne and one tonne of products per day, whilst a 10-tonne continuous line is under consideration.

Can a thread that melts really withstand the rigours of industrial production? According to Smart Stitch, it can be used on sewing machines already on the market, without altering the assembly line, and offers performance comparable to that of conventional threads. Since April 2026, the threads have been produced and distributed worldwide by the AMANN Group, one of the world’s leading manufacturers of sewing threads.

Recycling, however, is just one option. The same thread allows a seam to be unpicked to repair an item, replace a part or a zip, or remove labels and logos from an unsold garment before putting it back on the market. For one-off tasks, no specialised equipment is required: all you need is a heat press, a heat gun or an iron. There is also a detail of interest to designers: the heat-sensitive thread should not be placed everywhere, but only at the points where components need to be separated.

Protected by over 20 patents, the system is used in nearly a million products sold in more than 60 countries. Clients come from the fashion, sportswear, workwear and mattress sectors: H&M, Inditex, Sioen, Decathlon and BekaertDeslee. Footwear is currently one potential application, for example to replace a worn-out sole. But anyone familiar with an upper knows just how many seams, reinforcements and layers of adhesive hold it together, and how costly it is to separate them. It is in this area that the thread could prove its great utility.