Are Viscose and Rayon the same thing?

Yes, for practical purposes, but with a technical distinction. Rayon is the generic family name for all regenerated cellulose fibers. Viscose is a specific type of rayon made using the xanthate process (using Carbon Disulfide). Viscose accounts for roughly 80% of all rayon production.

Can Viscose be labeled as Bamboo?

No. Under FTC regulations, it must be labeled as 'Viscose from Bamboo' or 'Rayon made from Bamboo.' Labeling it simply as 'Bamboo' is a violation of federal law because the natural bamboo traits are eliminated during chemical regeneration.

Why Viscose Is Not a Natural Fiber

February 23, 2026

An old postcard shows an aerial view of a viscose manufacturing plant in virginia

Is Viscose a Natural Fiber?

No, Viscose is not a natural fiber. It is technically classified as a semi-synthetic, artificial, or regenerated cellulosic fiber. While it originates from a renewable natural polymer (cellulose from wood pulp or bamboo), the manufacturing process involves an irreversible chemical phase change that restructures the material from native Cellulose I to regenerated Cellulose II. This extensive chemical processing distinguishes it from natural fibers like cotton or wool, which are mechanically processed but remain chemically unaltered.

Viscose (often referred to as viscose rayon) occupies a complex taxonomic position between natural and synthetic fibers. International standard ISO 2076 defines it as a "man-made fiber" obtained by a manufacturing process, distinguishing it from materials that occur naturally in fibrous form. It is the most widely produced man-made cellulosic fiber (MMCF), accounting for approximately 80% of the market share for such materials.

1. Viscose vs. Rayon: The Taxonomy
2. Viscose Chemical Ontology: Cellulose I vs. Cellulose II
3. The Viscose Manufacturing Process
4. Viscose Regulatory Framework and Labeling
5. Environmental Impact of Viscose
6. References

1. Viscose vs. Rayon: The Taxonomy

While often used interchangeably by consumers, "Viscose" and "Rayon" have distinct technical and regulatory definitions. The relationship is best understood as Rayon being the genus (family) and Viscose being the species (type).

1.1 Rayon as the Umbrella Term

Rayon is the generic term utilized primarily in the United States for any fiber composed of regenerated cellulose, regardless of the specific manufacturing process. The U.S. Federal Trade Commission (FTC) defines rayon as a "manufactured fiber composed of regenerated cellulose". This broad category includes:

Viscose Rayon: Produced via the xanthation process using Carbon Disulfide. This is the most common type, making up ~79% of the rayon market.
Modal: A modification of viscose with higher wet strength and molecular orientation, often derived from beechwood.
Lyocell (e.g., Tencel™): Produced via a solvent spinning process (NMMO) without forming a xanthate derivative, resulting in a cleaner environmental profile.

1.2 Viscose as the Specific Process

Viscose specifically refers to rayon made using the "viscose process," which utilizes sodium hydroxide and carbon disulfide to solubilize the cellulose. Under ISO 2076:2021, "Viscose" is the mandatory legal generic name for fibers produced by this specific chemical route, while "Rayon" is listed as an alternative.

Regional Labeling Differences: In the United States, "Rayon" is the primary legal descriptor, though "Viscose Rayon" is permitted. In Europe, "Viscose" is the standard term. Therefore, a garment labeled "100% Rayon" in New York and "100% Viscose" in London likely contains the exact same fiber.

2. Viscose Chemical Ontology: Cellulose I vs. Cellulose II

Viscose Technical Profile

Classification: Regenerated Cellulose / Man-Made Fiber (MMCF)

ISO Generic Name: Viscose (Code: CV)

Chemical Structure: Cellulose II (Amorphous)

Degree of Polymerization: 400–700 (vs. ~10,000 in Cotton)

Key Reagents: Sodium Hydroxide (NaOH), Carbon Disulfide (CS₂)

Wet Strength: Low (loses 30–50% tenacity when wet)

The definitive scientific distinction between natural plant fibers and viscose lies in their crystallographic polymorphism. Native cellulose found in plants (e.g., cotton, wood) exists as Cellulose I, where polymer chains are arranged in parallel. Through the viscose manufacturing process involving solubilization and regeneration, this structure is thermodynamically altered into Cellulose II, where the chains are arranged in an antiparallel configuration.

2.1 Molecular Degradation

The transformation involves significant changes to the polymer chain length, known as the Degree of Polymerization (DP):

Native Cotton (Cellulose I): Possesses a high DP, typically between 8,000 and 15,000 anhydroglucose units.
Viscose Rayon (Cellulose II): The chemical aging process intentionally depolymerizes the cellulose to reduce viscosity, resulting in a much lower DP of approximately 250–600.

This reduction in polymer chain length explains why viscose is mechanically weaker than cotton, particularly when wet. Viscose loses 30–50% of its strength upon wetting due to its amorphous structure allowing high water absorption.

3. The Viscose Manufacturing Process

Viscose production is a "wet spinning" process that utilizes the xanthation route to solubilize the otherwise insoluble cellulose polymer. The process involves the following technically distinct stages:

3.1 Steeping and Shredding (Mercerization)

Dissolving wood pulp is treated with an 18% solution of sodium hydroxide (NaOH). This converts native cellulose into alkali cellulose and swells the fibers. The alkali cellulose is then mechanically shredded into "white crumbs" to increase surface area for reaction.

3.2 Aging and Xanthation

The crumbs are aged to depolymerize the cellulose chains. They are then reacted with carbon disulfide (CS₂) in rotating drums. This reaction substitutes hydroxyl hydrogen atoms with xanthate groups, forming sodium cellulose xanthate, which is bright orange. This step is critical as it renders the cellulose soluble in dilute alkali.

3.3 Dissolution and Ripening

The xanthate crumbs are dissolved in dilute sodium hydroxide to create the honey-like "viscose" solution. This solution is ripened for several days, filtered to remove undissolved materials, and degassed to remove air bubbles that could cause filament breakage during spinning.

3.4 Wet Spinning and Regeneration

The viscous solution is extruded through a spinneret (a nozzle with microscopic holes) into a coagulation bath typically containing sulfuric acid (H₂SO₄), sodium sulfate, and zinc sulfate. The acid neutralizes the alkali and regenerates the cellulose into solid filaments.

4. Viscose Regulatory Framework and Labeling

Due to the extensive chemical processing involved, global trade regulations strictly prohibit marketing viscose as "natural" to prevent consumer deception.

4.1 The "Bamboo" Labeling Fraud

The U.S. Federal Trade Commission (FTC) enforces the Textile Fiber Products Identification Act. The FTC explicitly states that textiles made from bamboo cellulose must be labeled as "Rayon made from Bamboo" or "Viscose from Bamboo". Labeling such products simply as "Bamboo" is a violation of federal law because the original bamboo plant does not exist in the final product; it has been chemically converted into rayon. The FTC has issued civil penalties exceeding $1 million to retailers for deceptive "bamboo" labeling claims.

4.2 ISO Standards

ISO 2076:2021 establishes the generic names for man-made fibers. It assigns the code CV to Viscose, defined as "regenerated cellulose obtained by the viscose process". It distinguishes Viscose from Modal (CMD) and Lyocell (CLY), which are also regenerated cellulosics but possess different distinguishing attributes and manufacturing processes.

5. Environmental Impact of Viscose

The classification of viscose as semi-synthetic brings specific environmental considerations distinct from natural fibers.

5.1 Chemical Toxicity

The primary environmental concern in viscose production is the use of Carbon Disulfide (CS₂). CS₂ is a neurotoxin associated with severe health risks for factory workers and can cause water and air pollution if released. While modern "closed-loop" facilities recover a significant percentage of these chemicals, traditional "open-loop" systems can release sulfur compounds into the environment.

5.2 Comparison to Lyocell

Viscose is distinct from Lyocell (e.g., Tencel™). While both are man-made cellulosics, Lyocell is produced using N-Methylmorpholine N-oxide (NMMO), a non-toxic organic solvent, in a process that recovers >99% of the solvent. This makes Lyocell a cleaner "third-generation" regenerated fiber compared to the "first-generation" viscose process.

6. References

```

Photo: This historic postcard showing an aerial view of the American Viscose Corp. plant in Front Royal, Virginia, is housed at the Boston Public Library and is reproduced under creative commons license 2.0.

Viscose is not a natural fiber, and for that reason you won't find it at ShirtCastle™.