silk

What is silk?

Silk is the one fiber that arrives already spun. A single Bombyx mori caterpillar builds its cocoon from one continuous filament, often more than half a mile long, wound around itself in about three days. Every other fiber on this list gets twisted together from short staples. Silk comes off the cocoon as one strand.

How silk is made

Cultivated silk starts with Bombyx mori, a moth domesticated so long it can no longer fly or feed itself. The caterpillar eats mulberry leaves and spins a cocoon from one filament of the protein fibroin, glued together with a second protein called sericin.

Here the ethics fork opens. To reel off one unbroken thread, most cocoons are steamed or boiled with the pupa still inside, before the moth can chew its way out and cut the filament. Peace silk (sold as ahimsa silk) waits for the moth to emerge, so the thread comes off in shorter spun pieces rather than one long reeled strand. You trade a little strength and shine for a live moth.

Either path ends at degumming: a hot alkaline soap bath that dissolves the sericin and uncovers the soft, high-luster fibroin underneath. Degumming is also where dyes and finishing chemicals go on. A fully degummed, carefully dyed silk carries little; a cheap, half-degummed, crudely dyed one carries the risk the fiber never had on its own.

Not all silk is the same

Silk splits by moth and diet. Mulberry silk, from farmed Bombyx mori raised on mulberry leaves, is fine, even, and near-white before dyeing, the thread behind most fine silk. Wild silk (tussah, eri, muga) comes from moths feeding in the open on oak or castor, so it reels coarser, more textured, and a natural tan or gold. Wild silk is often peace silk by default, since those moths finish their life cycle before harvest.

Is silk safe to wear?

Fibroin, the protein left after degumming, is one of the calmest things you can put on skin. It is smooth enough to create almost no surface friction, it breathes, and it carries moisture and heat away from your body, which helps eczema-prone and reactive skin stay settled. A properly finished silk earns the word hypoallergenic instead of only claiming it.

The old worry was residual sericin, the gum left behind when silk is under-degummed. Sericin was blamed for silk allergies for decades, but recent immunology finds the protein has low allergenicity on its own. The real added risk is the finishing: dyes and process chemicals applied during degumming cause skin trouble far more often than the fiber does. Buy fully degummed and certified and there is little left to react to.

• Almost no friction The smooth, round filament rubs and chafes less against sensitive skin than nearly any other textile, which is why it suits reactive and eczema-prone skin.
• Breathes and wicks Moves moisture and heat away from your body, so skin stays dry and calm instead of damp.
• Hypoallergenic when clean A fully degummed, well-finished silk is one of the few fabrics that earns the label rather than borrowing it from marketing.
• Works across seasons Feels cool in heat and holds a little warmth in cold, with no added finish doing the work.

OEKO-TEX Standard 100Global Organic Textile Standard

Doing this check on every product page yourself is the tedious part. The Toxome Chrome extension reads the composition for you while you shop, so you see whether something is silk (and what else is in it) before you buy, not after it arrives.

How silk affects the planet

Silk has the thinnest data in this whole guide. The often-quoted "worst fiber for water" figure traces back to a single small study, and its carbon estimates swing thirty-fold between studies, so no clean number is honest here.

What is clear is that silk is a protein fiber, so it biodegrades and sheds no plastic. Its real costs are energy and water in production, plus the ethics of how it is harvested.

Environmental figures are separate from the health score above, which reflects wearer health only. Numbers are per kilogram of finished fiber and rounded; see sources.

How silk is made

Conventional silk boils or steams the cocoons with the pupae still inside, to keep the filament in one unbroken thread. Peace silk, also called ahimsa silk, lets the moth emerge first and accepts the shorter, broken fibers that result.

A 2003 Human Rights Watch report documented hundreds of thousands of bonded children working in India's silk industry. That report is now over two decades old and conditions have reportedly improved, but current prevalence is not well documented, so read it as history, not a live statistic.

How to care for silk

Silk, answered