FabricTruth

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Lyocell, modal, viscose and bamboo rayon

These fibers start as trees or bamboo, so they’re often sold as natural. Regulators classify them as manufactured fibers, and FabricTruth counts them as non-natural. Here is why, and what each name means.

At a glance

Origin: Cellulose from wood pulp, bamboo or other plants, chemically dissolved and spun into new fiber.

How processed: Regenerated cellulose (often called semi-synthetic): plant cellulose is dissolved and re-formed. Viscose and modal use the viscose process with sodium hydroxide and carbon disulfide; lyocell dissolves pulp directly in an organic solvent.12

What it is and how it’s made

US textile rules define rayon as a manufactured fiber of regenerated cellulose. “Lyocell” is an allowed name for rayon made by precipitating cellulose from an organic solution, with no chemical intermediates.3

The US rule also adopts the ISO 2076 generic names, which tell viscose, modal and lyocell apart by how they are made.32

In the viscose process, pulp is treated with sodium hydroxide and carbon disulfide, then spun into an acid bath. Lyocell skips that chemistry and dissolves pulp directly in a solvent called NMMO.1

The FTC says soft “bamboo” fabric made by dissolving bamboo must be labeled “rayon made from bamboo” or “viscose made from bamboo”; only mechanically processed bamboo fiber can be called bamboo.4

How it wears

Viscose (rayon)Made by the viscose process, which uses carbon disulfide.13
ModalA viscose-process fiber made for high strength and a high wet modulus, by its ISO definition.2
Lyocell (often sold as Tencel)Spun from pulp dissolved in NMMO; published process studies report recovering more than 99% of the solvent.536
“Bamboo”Usually rayon or viscose made from bamboo pulp. US regulators fined Kohl’s and Walmart for selling it as plain “bamboo.”47
BiodegradationIn one aquatic test, rayon and cotton microfibers broke down while polyester barely did.8
How FabricTruth counts itNon-natural. Our score counts fiber that grows as fiber; regenerated cellulose is dissolved and rebuilt in a factory, and US rules list it as a manufactured fiber.3

Environmental notes

  • Carbon disulfide exposure in viscose plants has been linked to heart disease, nerve and eye effects, and reproductive and hormonal effects in workers.9
  • Lyocell avoids carbon disulfide, and its solvent is recovered in a closed loop.15
  • Being plant cellulose, these fibers can biodegrade, unlike polyester.8

Counterpoints and caveats

  • They’re plant-based and can biodegrade, so calling them “synthetic” overstates it. Regulators call them manufactured fibers, not synthetics.38
  • Lyocell is a much cleaner process than conventional viscose, so grouping them can be unfair to lyocell.59
  • The worker-health review was led by a consultant with an industry email address, and the biodegradation study was funded by the cotton industry.98
  • Counting them as non-natural is FabricTruth’s rule for a strict, label-based score, not a legal definition of “natural.”3

Buying tips

  • Read the generic name on the label: viscose, rayon, modal, lyocell and cupro are all regenerated cellulose.32
  • Be skeptical of “bamboo” on a soft tee unless the label says rayon or viscose from bamboo.47
  • If you buy one of these, lyocell avoids the carbon disulfide used for viscose and modal.1
  • Hemp or linen blended with lyocell, common in hemp shirts, is only partly natural; check the percentage.6

Common garments

  • Soft tees and underwear (modal, bamboo rayon)
  • Drapey camp shirts (viscose, lyocell)
  • Hemp or cotton shirts blended with lyocell
  • Jacket linings

Short answers

Is Tencel natural?

No. Tencel lyocell is wood pulp dissolved in a solvent and re-spun, and US rules treat lyocell as a kind of rayon, a manufactured fiber.35

Counterpoint: It’s plant-based, can biodegrade, and most of its solvent is recovered.

Is bamboo fabric natural?

Usually not. Unless it’s mechanically processed bamboo fiber, the FTC says it must be labeled rayon or viscose made from bamboo.47

Counterpoint: Bamboo grows quickly, but the fiber is still dissolved and re-spun like other viscose.

Is modal better than viscose?

Modal is a stronger, higher wet-modulus fiber made by the viscose process.29

Counterpoint: It shares the viscose chemistry, so the same worker-safety questions apply.

Where to find it

Scored brands have a natural-fiber share score; picks pages list specific products and are not scored.

We don’t list a brand or picks page for this yet.

    Related comparison: Cotton vs polyester T-shirts

    Sources

    Industry-funded, trade-body and advocacy sources are flagged. Product labels read October 31, 2026.

    1. 1Sayyed, Deshmukh, Pinjari. A critical review of manufacturing processes used in regenerated cellulosic fibres: viscose, cellulose acetate, cuprammonium, LiCl/DMAc, ionic liquids, and NMMO based lyocell. Cellulose, 2019.
    2. 2International Organization for Standardization. ISO 2076:2021 Textiles — Man-made fibres — Generic names. Standard, 2021.
    3. 3US Federal Trade Commission. Generic names and definitions for manufactured fibers (16 CFR 303.7). Code of Federal Regulations, Textile Rules, current.
    4. 4US Federal Trade Commission. How to avoid bamboozling your customers. Business guidance, current page.
    5. 5Sawiak, Souto, Lawson, Lo. Recovery of N-methylmorpholine N-oxide (NMMO) in lyocell fibre manufacturing process. Fibers, 2025.
    6. 6Toad&Co product page. Toad&Co Men’s Taj Hemp Shirt: 54% hemp, 44% Tencel lyocell, 2% elastane. Product label, read Oct 31, 2026, 2026.
    7. 7US Federal Trade Commission. FTC seeks largest-ever civil penalty for bogus bamboo marketing from Kohl’s and Walmart. Press release, 2022.
    8. 8Zambrano et al. (NC State, Cotton Incorporated). Microfibers generated from the laundering of cotton, rayon and polyester based fabrics and their aquatic biodegradation. Marine Pollution Bulletin, 2019. Funded by Cotton Incorporated; two co-authors from Cotton Incorporated.
    9. 9Gelbke, Göen, Mäurer, Sulsky. A review of health effects of carbon disulfide in viscose industry and a proposal for an occupational exposure limit. Critical Reviews in Toxicology, 2009. Lead author is a toxicology consultant listed with a BASF email; funding isn’t stated in the abstract.

    Updated October 31, 2026. All fiber guides · Why the label matters