Introduction
Sodium formaldehyde sulfoxylate — widely known as SFS or by the trade name Rongalite — is one of the most important reducing agents used in textile and industrial processing. Its ability to release active reducing power under controlled conditions makes it indispensable for discharge printing, reductive stripping, and bleaching of cellulosic and synthetic fibres.
For industrial buyers, understanding the technical profile of SFS — its chemistry, typical specifications, applications, and packaging — is the first step toward sourcing it correctly. This guide provides a practical technical overview for procurement and production teams.
What Is Sodium Formaldehyde Sulfoxylate (SFS)?
SFS is an organic sulfoxylate reducing agent derived from sodium hydrosulfite stabilized with formaldehyde. Its chemical identity is sodium hydroxymethanesulfinate, with the empirical formula CH₃NaO₃S and CAS number 149-44-0.
It appears as a white crystalline powder with a faint characteristic odour. Unlike the more aggressive sodium hydrosulfite, SFS offers a milder, more controllable reducing action, which is why it is preferred where process stability and fibre protection matter.
| Property | Typical Value |
|---|---|
| Chemical name | Sodium hydroxymethanesulfinate |
| CAS No. | 149-44-0 |
| Appearance | White crystalline powder |
| Assay (as SFS) | ≥ 98% |
| Insoluble matter | ≤ 0.05% |
| Iron (Fe) | ≤ 10 ppm |
| pH (1% solution) | 9.0 – 10.5 |
| Solubility | Freely soluble in water |
Specifications can vary by grade; the COA (Certificate of Analysis) issued per batch is the authoritative document for each delivery.
Applications of SFS in Textile Processing
Discharge Printing
SFS is the classic reducing agent for discharge printing on reactive, vat, and direct dyed fabrics. In discharge printing, a reducing paste is printed onto previously dyed fabric to destroy the colour locally, producing white or coloured patterns. SFS provides:
- Reliable colour destruction with controlled penetration
- Minimal fibre degradation on cotton, viscose, and blends
- Stable print paste viscosity for consistent pattern definition
Reductive Stripping
When dyed fabric has a shade fault, uneven dyeing, or needs to be recycled to a lighter ground shade, SFS is used for reductive stripping. The agent breaks the chromophore of many dye classes, allowing the fabric to be re-dyed. Typical conditions are an alkaline reducing bath with SFS at 2–5 g/L, processed at 60–90°C depending on fibre and dye type.
Reduction Clearing and Bleaching
In polyester dyeing, SFS is used for reduction clearing to remove surface dye and improve wash fastness. It is also applied in reductive bleaching sequences, often after oxidative stages, to achieve clean white goods.
Other Industrial Applications
Beyond textiles, SFS finds use across several industrial sectors:
- Polymer and rubber processing — as a polymerization initiator component and for trace catalyst removal.
- Sugar and food processing — in some regions, approved for sugar colour removal and bleaching applications (subject to local food-additive regulations).
- Chemical intermediate — as a starting material for specialty sulfoxylate derivatives.
- Water and wastewater — for targeted reduction of specific contaminants in niche applications.
Packaging and Export Specifications
SFS is a moisture-sensitive, reactive powder, so packaging must protect it from humidity, acids, and oxidizing agents throughout the supply chain.
| Packaging Option | Details |
|---|---|
| Standard bags | 25 kg PP woven bags with PE inner liner |
| Jumbo bags | 500 kg / 1,000 kg FIBC with liner |
| Palletizing | 40 bags per pallet, stretch-wrapped, with export marks |
| Container loading | 20 FCL / 40 FCL, with desiccant where required |
Ships are accompanied by COA, TDS, and SDS/MSDS documentation. SFS is generally transported as non-dangerous goods under ADR, RID, IMDG, and IATA, which simplifies export logistics and keeps lead times predictable. Always confirm the current classification with your supplier’s SDS before shipment.
Storage and Handling Guidelines
To preserve product performance, follow these storage principles:
- Store in a cool, dry, well-ventilated area, away from direct sunlight.
- Keep containers tightly sealed to prevent moisture absorption and caking.
- Avoid contact with acids and oxidizing agents — the product is a reducing agent.
- Use clean, dry equipment for handling; avoid generating dust clouds.
Quality Assurance and Documentation
At Vicmax Industrial, every batch of SFS is produced under controlled conditions and tested before release. SFS sits alongside a wider portfolio of textile and industrial chemicals, including monochloroacetic acid and sodium chloroacetate — see our comprehensive MCA guide and the sodium chloroacetate (SMCA) technical overview. For every product we provide:
- COA — per-batch analysis of assay, insolubles, iron, and other parameters
- TDS — physical and chemical property data for process design
- SDS/MSDS — safety and handling documentation in multiple languages
- Origin and export documentation — for smooth customs clearance
Our standard export quantity is a minimum of 1 metric tonne (1 MT), with container and bulk programmes available for regular buyers.
Conclusion
Sodium formaldehyde sulfoxylate (SFS/Rongalite) is a versatile, dependable reducing agent whose technical profile suits textile discharge printing, stripping, reduction clearing, and a range of industrial processes. Choosing a supplier who understands the chemistry, protects the product through packaging and logistics, and provides complete documentation protects your own process stability.
For specifications, COAs, and supply options, contact the Vicmax Industrial team.
External Reference: PubChem — Sodium hydroxymethanesulfinate (CAS 149-44-0) — chemical identification and property data
External Reference: AATCC — American Association of Textile Chemists and Colorists, test methods for textile processing
Vicmax Industrial — Specialty and industrial chemicals for global manufacturers. Tel/WhatsApp: +86 13382223993 | Email: [email protected]