Why I Prefer Natural Fibres — and When Polyester Still Has a Place
May 22, 2026 — Mercer St.
Most of my wardrobe is natural fibre. Cotton, silk, cashmere, wool, alpaca — these are the materials I reach for without thinking. The preference is not aesthetic snobbery or a categorical rejection of modern materials. It comes from a specific observation, repeated over years of wearing things and paying attention: natural fibres, on balance, feel better against the skin for extended daily wear.
But “on balance” is doing some work in that sentence. There are applications where polyester, nylon, and synthetic blends are genuinely the better choice. This note explains both sides of the argument, honestly.
In this note
- What natural fibres and synthetics actually are, structurally
- Why natural fibres tend to feel better for skin-layer and daily-wear applications
- Where synthetics outperform natural fibres — genuinely
- The environmental picture — which is more complicated than either side usually admits
- What this means for how I select pieces for Mercer St.
What the materials actually are
Natural fibres
Natural fibres come from plants (cotton, linen, washi) or animals (wool, cashmere, silk, alpaca). Plant fibres are cellulose-based. Animal fibres are protein-based. Both have structures that evolved over millions of years in the context of living organisms — which is relevant to how they interact with the human body.
Synthetic fibres
Synthetic fibres — polyester, nylon, acrylic, spandex — are produced from petrochemicals through industrial processes. They did not exist before the twentieth century. Man-made fibres such as viscose, modal, and lyocell are produced from plant sources (usually wood pulp) but through chemical processing that significantly alters the original plant fibre; they are sometimes called regenerated cellulose fibres to distinguish them from both natural and fully synthetic fibres.
Why natural fibres tend to feel better for daily wear
Moisture behaviour
Natural fibres absorb moisture. Cotton and linen absorb relatively quickly and hold moisture, which keeps them cool in heat but can feel heavy when saturated. Silk and fine wool absorb moisture more gradually and release it as conditions change — a behaviour sometimes called moisture buffering. This contributes to a relatively comfortable wearing experience across a range of temperatures and activity levels.
Synthetic fibres are generally hydrophobic. They repel moisture rather than absorbing it. In a garment worn against the skin, this means sweat and moisture tend to stay on the skin surface rather than being drawn into the fabric. For low-activity daily wear, this can make synthetics feel clammy or less comfortable over time.
Thermal behaviour
Natural fibres have a quality sometimes described as temperature-awareness. Silk feels cool at first contact and warms against the body. Fine wool insulates quietly without excessive heat retention. This behaviour comes partly from the fibre structure and partly from how the fibre manages moisture. It makes natural fibres comfortable across a wider range of temperatures than most synthetics.
Skin feel over time
A natural fibre garment worn well tends to feel better over time as the fibres settle and the fabric adapts to the body. A synthetic garment worn well tends to degrade — pilling, surface breakdown, static buildup — in ways that make it less pleasant with age. This is a generalisation with exceptions in both directions, but it reflects my consistent experience over years of comparison.
Mercer Note
None of this is an absolute statement. There are natural fibre garments that feel terrible and synthetic garments that feel fine. The fibre is one variable in a longer chain that includes yarn construction, fabric structure, finishing, and construction. A well-made synthetic garment can be more comfortable than a poorly made natural fibre one. The question is about averages and tendencies — not rules.
Where synthetics genuinely win
High-output physical activity
For running, cycling, climbing, and other high-output activities where managing large volumes of sweat quickly is the priority, synthetic technical fabrics — designed specifically for moisture-wicking, quick-drying, and mechanical stretch — outperform natural fibres. Merino wool is the natural fibre exception here; it performs unusually well for moderate-activity base layers. But for high-output activity, the technical synthetic is the appropriate tool.
Structured outerwear
Polyester and nylon are used in waterproof and wind-resistant outerwear because they can be constructed with the tight weave structures that natural fibres cannot match at the same weight. A down-filled jacket uses natural fill (or synthetic fill) inside a nylon or polyester shell precisely because the shell needs to be windproof and lightweight simultaneously.
Applications requiring very specific mechanical properties
Spandex (elastane / Lycra) provides stretch and recovery properties that natural fibres alone cannot match. In swimwear, compression garments, and applications where precise fit and recovery are essential, synthetic elastic components are necessary.
Durability in high-abrasion applications
In socks, nylon is added specifically because natural fibres alone wear through too quickly at the heel and toe. The Washi Knit Sneaker Socks in the Mercer St. collection use 38% nylon alongside the washi component precisely for this reason. Dismissing synthetics entirely from blended applications would mean accepting shorter-lived garments.
The preference for natural fibres is not a rule. It is a starting position based on experience — with specific, honest exceptions.
The environmental picture
The environmental comparison between natural and synthetic fibres is genuinely complicated, and both sides of the argument tend to overstate their case.
Synthetics are derived from fossil fuels, shed microplastics during washing, and do not biodegrade meaningfully. These are real environmental problems. But natural fibres are not automatically better: conventional cotton farming uses significant water and pesticides; wool production has land use and methane implications; silk involves the death of silkworm larvae. The lifecycle comparison depends heavily on the specific fibre, the farming or production method, and the end-of-life scenario.
A natural fibre garment worn for ten years is almost certainly better environmentally than a synthetic one worn for two. The durability and frequency of use matter more than the fibre category in most lifecycle analyses. This is one reason why the quality and longevity of a garment — not just its material — are part of the environmental equation.
What this means for Mercer St.
The Mercer St. selection starts from natural fibres — cotton, silk, cashmere, wool, alpaca — because this reflects my consistent experience of what works best for daily wear and skin-layer applications. Synthetic components appear in blends where they serve a specific function: nylon for durability in socks, polyurethane for stretch recovery in haramaki and some innerwear pieces, nylon facing in hats for structural requirements.
The goal is not categorical purity. It is to select the materials that make the garment work as well as possible for the purpose it is selected for — and to be honest about what each component is contributing and why.