A New Dyeing Architecture Challenges Established Textile Process Orthodoxy

The pre-coating step you developed appears to be one of the quiet but critical enablers of SUPRAUNO’s versatility. Could you take us inside the development process of that step — what problem were you attempting to solve when it emerged, and how did you validate that it would hold up across fibres from polyester to viscose to wool?
Swapneshu Baser: The pre-coating step did not emerge in isolation. It was a direct outcome of Deven Supercriticals’ long-standing engagement with supercritical fluid processing. As a company, we have worked with supercritical CO₂ for nearly three decades, designing and supplying more than 28 pilot-to-commercial-scale plants globally across multiple applications. This experience gave us a deep, practical understanding of how CO₂ behaves under different pressure–temperature regimes, with various substrates, and where its strengths and limitations lie.

When we examined prior art in supercritical CO₂ dyeing, one limitation stood out consistently: the inefficiency of dye dissolution and, consequently, its ineffective transport from one location to another. Whether the dye was placed in a dissolution chamber or introduced upstream, the process relied on CO₂ to first be able to solubilise the dye and then transport it through the textile mass placed in the dyeing vessel. This created fundamental constraints on process rate, shade uniformity, and the reproducibility of trichrome recipes.

The pre-coating concept was conceived and developed to eliminate these shortcomings. Instead of moving dissolved dye through textile layers, we uniformly pre-placed the dye on the entire textile surface, precisely where it is required to act for efficient dyeing. By pre-coating the textile with an optimum and precisely controlled quantity of dye and auxiliary chemicals, we dramatically increased the effective surface area of dyes available for interaction with supercritical CO₂. Under supercritical conditions, CO₂’s high diffusivity, low surface tension, and low viscosity enable rapid exhaustion of the dyes present on the textile surface, into the textile matrix, rather than relying on long-range transport of dyes from one textile layer to another.

A simple analogy to understand the improvement is the difference between the dissolving rate of a large sugar chunk versus powdered sugar in water. The increased surface area of the powdered sugar particles accelerates their interaction with water and increases the dissolution rate. The same physical principle applies here for pre-coated dyes in a thin layer, but in a supercritical environment.

Validation was empirical and rigorous. We tested the approach across multiple fiber chemistries and textile constructions, evaluating not only shade build-up but also uniformity, reproducibility, washing fastness, and finishing effects. Over the last four years, we have conducted more than 2,500 dyeing trials using textiles supplied by various mills and brands to build confidence in the effectiveness & versatility of our technology. The commercial-scale development of SUPRAUNO at Arvind Limited, in association with H&M, is the outcome of these consistently positive results.

Supercritical CO₂ dyeing has long been dismissed as too slow, too limited in fibre compatibility, or too expensive to scale. When you were building SUPRAUNO, which of those perceived ‘impossibilities’ posed the hardest scientific challenge, and how did you and your team push past it?
Swapneshu Baser: Supercritical CO₂ dyeing is not slow; in fact, it is significantly faster than conventional dyeing processes. Further, with the innovative SUPRAUNO technology, we can carry out single-step dyeing of polyester–cotton blends with a batch time of approximately two hours. In comparison, the conventional exhaust method requires two separate dyeing steps and typically takes eight to ten hours to achieve the same result. Importantly, our batch time remains around two hours across all textiles, including dark shades.

In terms of textile compatibility, SUPRAUNO is capable of processing woven, knitted, and even non-woven textiles across a wide range of man-made and natural fibers. These include cotton, polyester, nylon, viscose, linen, wool, acrylic, and their blends, all using supercritical CO₂ as the dyeing medium.

The inherently high efficiency of the SUPRAUNO process allows equivalent processing capacities to be achieved with smaller equipment sizes. This reduction in size of the vessels to process the same dyeing capacities is because of the experience that Deven Supercriticals has in the supercritical fluid space over the last three decades, which allowed us to create a simpler process and engineering. This results in a substantial reduction in capital investment compared with prior-art supercritical CO₂ dyeing technologies.

Your LCA data suggests major reductions in water, energy, and auxiliary chemicals, but that likely required aggressive optimisation of process times and dye utilisation. What were the biggest engineering battles behind achieving dyeing times that are less than half of both prior art and conventional processes?
Swapneshu Baser: The central engineering challenge was not making an existing dyeing process faster but eliminating the fundamental reasons why both conventional and prior-art CO₂ dyeing processes are slow. In conventional water-based dyeing, time is consumed by diffusion-limited exhaustion, repeated baths, fixation, washing, and multiple auxiliary chemical steps. The prior-art supercritical CO₂ systems avoided water but introduced new delays due to slow and inefficient dye dissolution, long circulation paths, and forced flow through multiple layers of textile loaded inside the dyeing vessel.

SUPRAUNO overcame these limitations by fundamentally changing where and how the dye is placed on the textile and how it interacts with supercritical CO₂. By pre-coating an optimum and precisely controlled quantity of dye directly onto the entire textile surface, we eliminated the need for pre-dissolution of the dyes and their long-range transportation. Under supercritical conditions, CO₂’s high diffusivity enables rapid exhaustion of dyes from the textile surface into the textile matrix, making solubility & penetration very efficient and uniform by design rather than by forced circulation.

This same architectural shift also made dyeing time independent from shade depth. In conventional processes, deeper shades require longer exhaustion times due to the sequential exhaustion of dyes to build the depth of the shade. In SUPRAUNO, shade depth is determined during the pre-coating step, and not through extended processing time, allowing dye transfer to proceed within a fixed kinetic window regardless of shade intensity.

Finally, optimisation of pressure–temperature ramps ensured that these gains translated into stable, repeatable industrial cycles. The result is a single-step dyeing process with batch times of approximately two hours—less than half of both prior-art and conventional methods—without sacrificing quality, uniformity, or scalability.

The inauguration of the first commercial-scale SUPRAUNO machine with Arvind and H&M Group marks a leap from innovation to industrial adoption. What were the key technical compromises or redesigns you had to make? Arvind is known for demanding industrial reliability, and H&M has its own stringent expectations on sustainability impact. What moments during the joint deployment made you realise just how high the bar was, and how did you keep the technology from being oversimplified or over-engineered during this collaboration?
Swapneshu Baser: The transition from a pilot-scale SUPRAUNO system to a commercial machine suitable for a high-throughput textile mill was not a reinvention exercise, but an application of industrial practices Deven Supercriticals (DSPL) has refined over more than 25 years. Before entering textile dyeing, we had already designed, manufactured, and supplied 28 pilot to commercial-scale supercritical fluid processing plants globally, across various applications such as tea-coffee decaffeination, herbal extraction, spice oil processing, leather processing, etc. That experience shaped the scale-up from the outset.

Several features critical to industrial textile operation were therefore inherent rather than newly introduced. The mirror-polished internal surfaces of the pressure vessels, for example, are a standard DSPL practice for easy cleaning between the batches. In the context of dyeing, this becomes especially important, as it prevents dye deposition and enables mills to switch between colors with minimal cleaning or disruption to production.

Ease of operation was addressed through an ingeniously designed bolt-less and quick opening and closing mechanism for high pressure dyeing vessel, combined with a centrally controlled HMI that allows operators to monitor and control the entire process from a single location. This ensured that the system could be run by existing mill personnel without added operational burden.

Similarly, safety was not an afterthought introduced during scale-up. Multiple safety interlocks, third-party inspections, and international certifications have always been core to Deven Supercriticals’ approach. This continuity in safety and quality was essential in translating a laboratory breakthrough into a dependable industrial reality.

Supercritical CO₂ systems are complex pressure vessels, yet the textile industry is accustomed to fast, water-based processes. What did it take — technically and culturally — to convince mills that your technology could be operated by their existing workforce without demanding a new breed of specialist technicians?
Swapneshu Baser: One of the central design objectives of SUPRAUNO was to ensure that technological sophistication did not translate into operational complexity. From the beginning, we were clear that industrial adoption would only happen if the system could be run by the existing mill workforce, not require a new class of supercritical-fluid specialists.

Technically, this meant simplifying the process architecture wherever possible. SUPRAUNO deliberately eliminates continuous CO₂ circulation, complex fluid routing, and flow-dependent dye transport that are common in earlier supercritical systems. By using conventional dyes and standard tri-chrome recipes, the technology builds directly on the existing expertise of the dye master, rather than replacing it. The chemistry and shade development logic remain familiar, even though the dyeing medium changes from water to carbon dioxide.

Operational simplicity is reinforced through a PLC-based, centrally controlled HMI. All critical parameters—pressure, temperature, time, and safety status—are monitored and controlled from a single interface, allowing operators to oversee the entire cycle without manual intervention or distributed control points. This reduces cognitive load and makes training straightforward.

Commercial dyeing lines run on tight economics, and SUPRAUNO eliminates steps like reduction clearing for polyester or salt-driven dyeing for cotton. What insights from the trials on diverse fibres and blends helped you prove, convincingly, that the operating economics would hold up in the real world and not just on paper?
Swapneshu Baser: Over the last four years, we have conducted more than 2,500 dyeing trials on the prototype plant at our facility that has been designed to mimic features of the actual scaled-up operation. These trials were conducted in collaboration with multiple mills and industry partners across fibers, blends, textile constructions, and shade ranges. These trials were critical in stress-testing not only technical performance, but also repeatability, uptime, changeover behavior, and total operating cost under mill-like conditions. Subsequently, this technology and consumption, economic numbers have now been proven on the bulk scale as well, with production starting at Arvind Limited.

In conventional cotton dyeing, salt is added to drive dye exhaustion by suppressing electrostatic repulsion in an aqueous bath. In SUPRAUNO, water is replaced by supercritical CO₂, which behaves like a liquid in its solvating power and like a gas in its diffusivity, low surface tension, and low viscosity. These properties enable efficient and uniform exhaustion of dyes into the fiber matrix without the need for salt.

In polyester dyeing, repeated trials showed consistently high dye utilisation and fixation within the fiber matrix. Because the dye is effectively exhausted and fixed during the supercritical cycle itself, there is low residual unfixed dye to remove. This eliminates the need for reduction clearing without compromising shade accuracy or fastness.

You’ve described this machine as not just a technological milestone but a step towards safeguarding water, energy, and health for future generations. Looking back, what personal or organisational decisions were hardest—the ones without which SUPRAUNO might never have left the lab? 
Swapneshu Baser: Over the last four years, the team carried out over 2,500 dyeing trials on the prototype plant using textiles supplied by multiple mills and brands. This work was essential to refining the process, addressing fiber-specific challenges, and demonstrating repeatability across constructions, shades, and blends. Building confidence in a new dyeing medium required evidence generated through repeated, real-world trials.

Being selected as an innovator by ‘Fashion for Good’ also played an important role in accelerating execution and learning about industry needs. It enabled structured engagement with brands, mills, and technical experts, providing practical feedback on performance expectations, operational constraints, and sustainability requirements that could not be replicated in a laboratory environment.

Equally important was the support of professionals across the textile industry, dye / auxiliary manufacturers, who shared their experience regarding dyeing behavior, auxiliary systems, and process limitations. Their inputs helped translate SUPRAUNO from a controlled prototype into a commercially deployable technology.

Without this sustained collective effort across engineering, industry partnerships, and real production trials, SUPRAUNO would not have progressed from the lab to commercial reality.

With India’s first commercial installation now running and global attention growing, what do you see as the next frontier—is it deeper fibre versatility, tighter integration with circular textile feedstocks, or entirely new applications of supercritical fluid technology that the industry hasn’t imagined yet?
Swapneshu Baser: With the first commercial installation now running, the immediate next frontier is scaling SUPRAUNO into mills globally where legal compliance pressures, environmental constraints, and brand expectations are converging. Many mills today face increasing difficulty in meeting water, energy, chemical, and effluent regulations, while simultaneously trying to move up the value chain to attract truly compliant international brands. SUPRAUNO addresses these challenges directly by enabling mills to reduce environmental impact at the process level, while expanding their capability to dye a wider range of textiles and blends with fewer steps and lower operating complexity.

At the same time, we see a strong opportunity to extend the technology upstream. We are actively working on commercial-scale SUPRAUNO solutions for yarn and fiber dyeing using the same machine architecture. These developments are aimed at enabling earlier-stage coloration with the same benefits—waterless processing, high dye utilisation, and reduced auxiliary chemicals—and are expected to be introduced in the coming year.