Yak down

Overview

The fine insulating undercoat of yaks, separated from coarser outer hair.

Feel and behavior

Soft, warm and often used in natural brown tones.

Where you find it

Knitwear, scarves, blankets and wool blends.

Source and geography

Yak fiber comes from the domestic yak, Bos grunniens, a bovine of the Qinghai-Tibet Plateau whose dense coat is a key cold adaptation; herds sampled in one Sichuan study lived at roughly 3,100 to 4,200 m. The coat is layered: coarse outer hair, including the long flank or skirt hair that distinguishes yak from other cattle, over a fine down. Breeds differ in color, and the Tianzhu White Yak is studied specifically for hair yield and length. Reliable global volume figures for yak down could not be verified here.

Worth knowing

• On family yak farms studied on the Qinghai-Tibetan Plateau, methane and nitrous oxide together made up about two-thirds of annual global warming potential.
• Hand-dehaired yak down measured coarser on average than machine-dehaired down in one fiber study, because more guard hair remained.

Types, grades and fabrics

Types and grades

Yak fiber comes in two main forms: fine down, the insulating undercoat collected at the molt and dehaired for textiles, and coarse outer hair traditionally used for ropes, tents and rugs. Reported down diameters are roughly 16 to 20 microns, overlapping the coarser end of cashmere, with average down length of about 3.5 to 5 cm in one study of grey and black yaks. Hand dehairing tends to leave more coarse hair and raise the average diameter. Color is the other key variable: most yak fiber is brown, grey or black, while white down from breeds such as the Tianzhu White Yak is scarce. Trade forms include dehaired down, tops, yarn and blends, especially yak with merino.

Fabrics and products

Dehaired yak down is spun into knitting yarn and made into sweaters, scarves, hats and socks, often in natural brown or grey. Blends with merino wool add elasticity and length for base layers and outdoor knitwear, and blends with silk add luster to scarves. Woven yak and wool cloth is used for throws, blankets and some coatings. Coarse yak hair appears in felted and woven rugs, bags and traditional tent cloth on the plateau. Undyed yarns are common because bleaching to pale shades costs fiber strength.

Buying and care

How to judge quality

Ask for 'yak down' rather than 'yak hair' or 'yak wool', since the terms can hide a coarse fraction. Good yak down feels soft and dry with a matte surface; visible straight, dark, stiff fibers indicate poor dehairing and will prickle. Very pale yak products have been bleached, which can weaken fiber and harshen hand. Check blend percentages: 'yak blend' may be mainly wool. Because yak down is a documented adulterant in cashmere, a product labeled cashmere should not contain it, and a cheap 'cashmere' in natural brown deserves questions. In the US, yak must be named with the word hair or fiber, not called wool or cashmere.

Care in detail

Follow the label. Hand wash in cool water (about 30 C or below) with a wool detergent free of enzymes and bleach, or use a wool cycle only if permitted. Avoid rubbing and wringing; press water out, roll in a towel and dry flat. Never tumble dry. Steam or press at the two-dot setting (up to 150 C) through a cloth if needed. Remove pills with a comb or shaver once early pilling settles. Fold for storage, keep pieces clean, and protect them from moth and carpet beetle larvae with sealed storage and regular checks.

Care at a glance

Follow the label and treat fine down knits gently. Reshape and dry flat rather than hanging.

Environmental and social footprint

Yak down is a co-product of plateau herding, so its footprint is tied to how pastures are grazed rather than to fiber-specific inputs. A 2017 study of family yak farms on the Qinghai-Tibetan Plateau measured greenhouse gases from meadows, dung, manure heaps and night pens and found that methane and nitrous oxide made up about 21% and 45% of annual global warming potential, so gases other than carbon dioxide cannot be ignored. Grazing intensity matters: in a 2024 yak grazing experiment on the eastern plateau, heavier grazing reduced ecosystem multifunctionality and carbon and nitrogen cycling. No peer-reviewed life cycle assessment per kilogram of yak down was found. Herder income from down depends on collection and dehairing, and bleaching pale yak adds chemical inputs.

Tradeoffs

Collection methods, dehairing yield and herder compensation vary. Scarcity alone does not demonstrate responsible production.

A useful question to ask: Who collected the down, and how was it separated, graded and purchased?

Science

Data sheet

Protein-based natural material

Most hair is keratin; silk is a different protein-fiber system.

Structure and chemistry

Yak down and hair are keratin fibers with a cuticle, cortex and, in coarser fibers, a medulla. The down resembles cashmere closely enough that the two are hard to separate by appearance; an untargeted proteomic survey identified 156 proteins in yak, 174 in cashmere and 157 in wool fibers, with substantial sequence homology among them. Most yak fiber is naturally dark because of melanin granules in the cortex. Unpigmented belly hair studied as a model showed higher porosity than human hair at every structural level, a lower Young's modulus, smaller intermediate filament spacing and fewer overlapping cuticle scales, features that ease dye uptake.

From source to yarn

The coat follows a seasonal cycle of anagen, catagen and telogen, with WNT and FGF signaling active in growth and BMP and DKK1 signals in regression, so down is collected around the molt. Raw fiber is scoured and dehaired to separate down from outer hair, as with cashmere. Because most fiber is brown or black, pale shades require bleaching: one study used a melanin-targeted Fenton process in which iron ions bound to melanin catalyze hydrogen peroxide decomposition, and ultrasound raised the whiteness index from 11 to 45 with about 15% loss of tensile strength. Bleached or natural fiber is then carded and spun.

Performance in use

Dehaired yak down behaves like other fine keratin: hygroscopic, warm when slightly damp, self-extinguishing in flame and receptive to acid dyes, although its natural brown limits the palette unless bleached, and bleaching partly cleaves disulfide bonds and roughens the cuticle. Fine down in lightly twisted yarn pills and abrades more readily than long worsted wool, and residual outer hair raises prickle and coarsens the handle. Like all protein fibers it needs protection from clothes moth and carpet beetle larvae, and alkaline washing weakens it.

How it is identified

Burn tests (indicative only, and to be done with care) cannot separate yak from wool or cashmere. Microscopy of scale pattern and diameter is the accepted commercial method but depends on the operator. Species-specific keratin peptides measured by LC/ESI-MS or by targeted parallel reaction monitoring distinguish yak, wool and cashmere and can quantify blends, even in chemically treated fabric. ATR-FTIR with chemometrics and MALDI-TOF peptide profiling have also separated yak from other specialty hairs. Undeclared yak in cashmere is the main labeling risk.

History

Timeline

1. 2016Untargeted proteomics identified 156 proteins in yak fiber against 174 in cashmere and 157 in wool, supporting species discrimination. [2]
2. 2017Measurements on Qinghai-Tibetan Plateau family yak farms found methane and nitrous oxide made up about two-thirds of annual global warming potential. [4]
3. 2022An ultrasonic, melanin-targeted Fenton bleaching method raised yak hair whiteness index from about 11 to 45 with about 15% tensile strength loss. [3]
4. 2024A yak grazing experiment on the eastern Tibetan Plateau found heavier grazing reduced ecosystem multifunctionality. [5]

Yak coats have supported textile use in high-plateau pastoral communities. Fine down and coarse outer hair serve different purposes. Contemporary luxury yarn markets emphasize the dehaired undercoat, one part of a broader material tradition.

The deeper record

Yak coats have long served plateau pastoralists, while the fine down reached international knitwear markets more recently through industrial dehairing. Much current research is Chinese and genomic: single-cell and transcriptome atlases of yak hair follicles and genome-wide association studies of hair weight and length in the Tianzhu White Yak are framed explicitly as ways to make fuller use of yak fiber and support pastoral economies. Researchers also describe yak hair as a widely available but underexploited dark fiber, and have tested byproduct uses such as bioplastic films made from discarded hair.

Labeling and law

Yak is not among the specialty fibers named in the US Wool Products Labeling Act, so its content is disclosed under the textile rules: 16 CFR 303.6 allows the animal's name with the word hair, fiber or blend, for example yak hair, when the fiber is 5% or more of the product, or the collective term fur fiber when no claim about the animal is made. Yak must never be labeled cashmere. In the EU, Annex I of Regulation (EU) No 1007/2011 lists yak among the named fine animal hairs, followed or not by wool or hair.

This describes what rules and standards cover. It is not legal advice; jurisdiction, product form and current rule text control.

Frequently asked

Is yak wool as soft as cashmere?

Fine yak down, reported at roughly 16 to 20 microns, overlaps the coarser end of cashmere, so well-dehaired yak can feel similar. Softness depends on how thoroughly coarse hair was removed and on yarn and knit construction, so compare actual garments rather than fiber names.

Why is most yak yarn brown?

Most yaks have dark, melanin-rich coats, so the down is naturally brown, grey or black. White yak is scarce, and pale shades usually require bleaching, which can weaken the fiber and roughen its surface. Many makers therefore sell yak undyed or overdyed in dark colors.

How is yak labeled in the US?

Yak is not one of the specialty fibers named in the US wool law, so it is disclosed under the textile rules as yak hair or yak fiber when it makes up 5% or more, or under the general term fur fiber. It must never be called cashmere.

Sources

• Food and Agriculture Organization: Harvesting of textile animal fibres
• PLOS One: Combining untargeted and targeted proteomic strategies for discrimination and quantification of cashmere fibers (2016)
• Journal of Mass Spectrometry: Identification and quantification of different species in animal fibres by LC/ESI-MS analysis of keratin-derived proteolytic peptides (2013)
• Ultrasonics Sonochemistry: An efficient ultrasonic-assisted bleaching strategy customized for yak hair triggered by melanin-targeted Fenton reaction (2022)
• Molecules: Porosity at different structural levels in human and yak belly hair and its effect on hair dyeing (2020)
• eCFR: 16 CFR 303.6, Generic names of fibers to be used
• Journal of Natural Fibers: Determining the effect of pigmentation on some physical and mechanical properties of yak and cashmere down fibers (2022)
• Scientific Reports: Key sources and seasonal dynamics of greenhouse gas fluxes from yak grazing systems on the Qinghai-Tibetan Plateau (2017)
• Science of the Total Environment: Belowground diversity drives multifunctionality in grazing pastures on the eastern Tibetan Plateau (2024)
• GINETEX: Care symbols (ISO 3758 care labelling system)

Cite this page

Chaos. (2026). Yak down. In Fibers of Earth: An independent textile atlas. https://www.hendrickresearch.com/fibers/materials/yak/