What is modal?
Modal is a softer wood-based fiber, usually made from beech wood by a tweaked viscose process. Like all viscose, it still uses carbon disulfide, a harsh chemical. But the brand-name version, TENCEL Modal, captures and reuses 99 percent or more of its chemicals and water in a closed-loop system, meaning the factory recycles them instead of dumping them.
Modal, a stronger, softer refinement of viscose, dates to 1950s Japan. Lenzing, the Austrian maker behind the TENCEL brand, scaled it up in the 1960s, decades before its closed-loop TENCEL process existed.
How modal is made
Modal starts as beech pulp run through the viscose chemistry: steeped in sodium hydroxide (caustic soda), then reacted with carbon disulfide, the same two chemicals that drive ordinary viscose. Modal uses less caustic soda and stretches the fiber as it forms, giving it a higher wet modulus, industry shorthand for a fiber that keeps its strength wet and resists the shrinking plain viscose suffers.
From there the mill matters more than the wood. Generic modal runs that carbon-disulfide process with no promise about how its chemicals or wastewater get handled. TENCEL Modal recovers about 95 percent of its process chemicals and comes in a certified carbon-neutral version, though it stops short of the fully closed loop TENCEL Lyocell reaches, because modal's chemistry still leans on carbon disulfide.
Either version comes out silky, fine, and absorbent. The gap between the two sits at the mill, not in the wood.
Not all modal is the same
Modal on a label can mean two different processes. Generic modal is ordinary carbon-disulfide viscose with no guarantees behind it. TENCEL Modal is the same base fiber made with high chemical recovery, certified wood sourcing, and finished-fiber safety testing.
Is modal safe to wear?
Modal feels silky and fine against skin, absorbs moisture, and breathes, so it stays comfortable in heat. The health question is who made it. Generic modal runs the carbon-disulfide process, hard on the workers who make it, with no promise about leftover chemicals or the easy-care coatings added later, some of which release formaldehyde, a skin irritant.
TENCEL Modal recovers most of its chemicals, sources its beech from certified forests, and tests the finished fiber as safe against skin. Both feel the same to wear. The certainty about leftovers and coatings, not the softness, separates them.
- Soft and fine One of the smoothest wood-based fibers, with little of the rubbing that causes irritation.
- Absorbs moisture well Soaks up sweat and releases it, so it stays comfortable rather than clammy in heat.
- Keeps its strength wet Its high wet modulus resists the shrinking, stretching, and pilling that plain viscose develops after washing.
Generic modal runs the ordinary carbon-disulfide viscose process, so it defaults to 70. Disclosing the branded TENCEL Modal process, which Lenzing's Higg data puts at up to 71 percent lower global-warming impact than generic modal, lifts that to 78, better than regular viscose but short of a true closed-loop lyocell, because modal's chemistry still relies on carbon disulfide. See the full method.
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 modal (and what else is in it) before you buy, not after it arrives.
How to care for modal
shop modal
Modal, answered
Generic modal runs the same carbon-disulfide process as regular viscose, so leftover chemicals and added finishes are the concern, not the beech wood. TENCEL Modal recovers most of its chemicals and tests the finished fiber, which is the safer bet if you are picky about it.
Yes. Both start as beech dissolved the viscose way, but TENCEL Modal recovers about 95 percent of its chemicals, offers a certified carbon-neutral version, and checks its wood sourcing, while generic modal makes no such promise.
Less than regular viscose. Modal is high-wet-modulus rayon, meaning it holds its strength when wet, so it resists the shrinking and stretching plain viscose is prone to. Wash cool and dry low to keep it that way.
For softness and moisture handling, many people prefer it. For a guaranteed clean production process, only certified organic cotton or TENCEL Modal, not generic modal, gives you that assurance.
- What are TENCEL Lyocell and Modal Fibers · Lenzing / TENCEL
- A review of health effects of carbon disulfide in the viscose industry · PubMed
- OEKO-TEX STANDARD 100 · OEKO-TEX
The health score reflects wearer health only and mirrors the Toxome app. This guide is educational and is not medical advice.