What is MTO — and what is white petrol?
MTO stands for Mineral Turpentine Oil. It is a petroleum distillate — a fraction of crude oil refined to a specific boiling range. In industrial contexts it is used as a paint thinner, a cleaning solvent for machinery, and a degreaser. It is cheap, widely available at any hardware shop, and effective at dissolving oil and grease from fabric.
White petrol is a closely related product — a lighter petroleum fraction sold under a different local trade name. In some regions, dry cleaners use kerosene or crude petroleum spirit for the same purpose. These are all petroleum hydrocarbons. They share the same fundamental chemistry, the same regulatory classification, and the same risks.
MTO and white petrol are not the same as professional hydrocarbon dry cleaning solvent. Professional dry cleaning uses a highly refined, purified hydrocarbon solvent processed to remove aromatic compounds. The two are chemically different and their safety profiles are completely different.
Why do unorganised dry cleaners use it?
The answer is economic. A professional dry cleaning machine costs ₹8–20 lakhs. Professional hydrocarbon solvent costs ₹800–1,200 per litre. MTO costs ₹50–80 per litre from any hardware supplier and requires no special equipment — a brush, a cleaning table, and a hand-applied solvent process.
"In the absence of mandatory solvent regulation for small dry cleaners in India, the practice of using MTO continues entirely on economic grounds."
India's unorganised dry cleaning sector represents the vast majority of establishments by number. Without licensing requirements or solvent regulation, the economics of MTO-based cleaning are so asymmetric that the practice will continue until consumer awareness changes demand.
The health concern — what residue does it leave?
Petroleum solvents do not evaporate completely. When MTO is applied to fabric, a portion penetrates the fibres. The lighter fractions evaporate, but heavier aromatic and aliphatic compounds stay in the fabric as residue. These compounds are what concern toxicologists.
| Compound | Classification | Route |
|---|---|---|
| Petroleum distillates | IARC Group 2B (possible carcinogen) | Skin absorption, inhalation |
| Polynuclear aromatic hydrocarbons (PAHs) | Several IARC Group 1 (carcinogenic) | Skin absorption from fabric |
| Professional hydrocarbon solvent | Not classified as carcinogen when used correctly | Minimal — sealed machine |
The exposure route that concerns dermatologists is skin absorption from fabric contact. When clothing cleaned with MTO is worn against skin for hours — a silk saree, a woollen suit, a kurta — any residue transfers to the skin surface.
Silk is particularly vulnerable to retaining solvent residue because its protein fibres are highly absorbent. Kolkata's silk-intensive wardrobe — sarees worn year-round — makes this a specific concern for the city.
The professional standard — how sealed machines differ
Professional dry cleaning uses a fundamentally different process. In an enclosed automatic machine, the garment enters a sealed drum. Hydrocarbon solvent circulates in a closed loop. After cleaning, the solvent is extracted and filtered. The garment dries inside the same sealed system.
The Swiss Laundry has operated sealed automatic machines at Kasba, Kolkata since 2013. This is the only standard we accept.
How to check whether your dry cleaner uses safe solvents
Ask directly: what solvent do you use? A professional dry cleaner will answer immediately. Safe answers: hydrocarbon solvent, Perc (perchloroethylene), or GreenEarth. Unsafe answers: petrol, white petrol, MTO, thinner, or evasion.
Also look for an enclosed drum machine. If you cannot see one, no automatic dry cleaning is happening. A brush and a vat of solvent is the MTO method.
Ask: "What solvent do you use for dry cleaning?" If they cannot name it, they almost certainly use one they know customers would reject.
The Swiss Laundry has used professional-grade hydrocarbon solvent in fully enclosed automatic machines since 2013. No MTO. No open-process cleaning. No petroleum residue on returned garments. 13 years of the same standard — before it became a conversation.