What Is DownTek™? The Complete Guide to Hydrophobic Down

This distinction - treatment on the down, not the shell - is what makes DownTek™ genuinely different from a standard DWR-coated outer fabric. A shell's DWR finish sheds water from the outside surface. DownTek™ works from the inside, at the level of the insulation itself. Both elements play a role in a complete down jacket system, but they are addressing different problems. The shell fabric helps keeps water out. DownTek™ ensures that any moisture that does get in through rain, seam penetration, or internal perspiration helps delay compromising the insulation's performance.

Traditional down is highly hygroscopic meaning it readily absorbs water. The fine filaments that make up each cluster have a natural affinity for moisture, which causes them to bond together when wet, collapsing the three-dimensional structure that traps air. DownTek™ ZeroPFC™, the specific variant used in all Jöttnar down products, uses a lipid-based nanotechnology treatment derived from naturally occurring lipids (fats). This treatment is applied to each individual down cluster at a molecular level, coating the filaments with a layer that creates surface tension against moisture. When water contacts treated down, it cannot be absorbed into the filament structure. Instead, water molecules bead on the surface and roll off, the same principle as water beading on a waxed surface.

The application process matters as much as the chemistry. DownTek™ treatment is applied in controlled closed-loop treatment baths, a process designed to prevent chemical runoff and local water pollution. The treatment solution is contained within the system rather than discharged into local waterways. Each batch of down is treated, tested and certified before leaving the facility.

The nano-level application means the treatment integrates with the filament structure itself rather than sitting as a surface coating. This is why it does not affect the feel, softness or loft of the down. And it is why the treatment does not wash out: it is bonded to the filament at a molecular level, not adhered to the surface where it could be gradually abraded or washed away.

The original method for creating hydrophobic down used perfluorocarbons (PFCs), specifically PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid), both C8 long-chain carbon compounds. PFCs are highly effective at repelling water, but they are persistent in the environment: they do not break down, have been found in human blood and wildlife globally, and are classified as substances of very high concern. PFOA is considered a toxicant and carcinogen. PFOS is a volatile sulfonamide that has been found to compromise the immune systems of both humans and animals.

Jöttnar uses DownTek™ ZeroPFC™ exclusively - a treatment that achieves the same hydrophobic performance using bluesign® approved chemistry that contains no PFCs or PFAS (per- and polyfluoroalkyl substances) of any kind. The lipid-based chemistry is derived from naturally occurring fatty acids, is non-hazardous, non-toxic, and safe throughout the product lifecycle. Bluesign® approval means the chemistry and the process have been independently verified against environmental and safety standards in textile manufacturing - a third-party verification rather than brand claim.

The performance figures cited throughout this guide - the 1,500 minute test result, the 33% less moisture absorption, the 66% loft retention - all apply to the PFC-free ZeroPFC™ variant. This is not a compromise between performance and environmental responsibility. The PFC-free formula outperforms harmful formulas on the standardised shake test: 1,500 minutes vs 1,000 minutes (see below). Removing the harmful chemistry improved the performance.

The difference between treated and untreated down is not marginal. DownTek™ performance is measured using the IDFL (International Down and Feather Testing Laboratory) shake test, a standardised industry measurement developed specifically to quantify DWR down performance. The test places a sample of down in a sealed jar with a standardised quantity of water on an oscillating machine. Saturation levels are measured at intervals until the down is completely submerged, meaning the clusters have fully collapsed and insulation has failed.

A note on the shake test: the test involves down in direct and constant contact with water for the full duration this being a more extreme exposure than many real-world conditions. In actual use, DownTek™ treated down performs across a longer effective window than the test can directly measure. The test is useful as a comparative tool; the real-world application is usually less severe. What the test definitively establishes is the magnitude of the difference between treated and untreated down, which is the relevant data point for a buying decision.

No, the DownTek™ treatment does not wash out. Many DWR treatments on shell fabrics degrade with washing and use, requiring periodic reapplication. DownTek™ treatment is bonded to the down filaments at a molecular level. Unlike topical treatments, it does not wash out over repeated launderings, which means the hydrophobic performance of the down is maintained throughout the jacket's lifespan.

In light rain or snow: treated down maintains full performance. Untreated down begins absorbing moisture and losing loft within minutes. Under a shell in heavy rain: both perform similarly as the shell is doing its job, and DownTek™ provides insurance for the moments when moisture penetrates. During high-output activity: perspiration is the primary moisture challenge for down in mountain use, and DownTek™-treated down is significantly less compromised by internal moisture than untreated down. After getting wet treated down dries three times faster, meaning recovery time between uses is substantially shorter.

One practical maintenance note: tumble drying on a low heat setting as part of regular care or as a standalone step reactivates the DownTek™ treatment and restores optimal hydrophobic performance if you notice any reduction over time. The treatment is permanent, but the thermal reactivation refreshes it to peak performance. This is worth doing at the start of each season before the jacket sees demanding use. See our down jacket care guide for full washing and storage instructions.

Frequently asked questions.

Does DownTek™ work in very heavy rain?

DownTek™ treats the down clusters themselves, not the shell fabric. DownTek™ provides insurance for moisture that penetrates the shell or enters through perspiration. In heavy rain, layer a waterproof shell on top of your down jacket.

Is DownTek™ down warmer than regular down?

At equivalent fill power and fill weight, DownTek™ treated down is warmer in practice in wet conditions because it retains loft where untreated down would lose it. In dry conditions, both perform equivalently.

Does DownTek™ affect the feel of the down?

No, the treatment is applied at a molecular level to the filament surface and does not affect the down's softness, loft or feel.

Which Jöttnar down jackets use DownTek™? All of them. DownTek™ ZeroPFC™ is standard across the entire Jöttnar down range.