Sugar soap
Contains no sugar and, in most modern products, no soap. An alkaline pre-paint cleaner whose name is a description of what it looked like, not what it is.
What not to do
Sugar soap is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
- Rinse thoroughly afterwards
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate in water solution reacts with aluminium, zinc and galvanised iron to produce flammable hydrogen gas and may corrode brass and steel when wet. (states this directly)
AAMA 609 & 610-02: Cleaning and Maintenance Guide for Architecturally Finished Aluminum
American Architectural Manufacturers Association (AAMA), 2002 · Standards body
Relied on for: That cleaners containing trisodium phosphate must not be used on anodised surfaces. (states this directly)
Sugar soap is unsafe on Oiled wood
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Test on an inconspicuous area first
Evidence
Strongly supported
Sources
Maintenance, and How to Clean and Take Care of Your Wood Floors
National Wood Flooring Association (NWFA) · Trade or professional body
Relied on for: That the cleaner must be one made specifically for the finish, and that inappropriate cleaners strip the finish and cause permanent damage. (states this directly)
Precautions
- Wear gloves
- Wear eye protection
- Rinse thoroughly afterwards
- Never mix with other cleaning products
- Check the manufacturer's instructions
In detail
Sugar soap is the British decorator's standard preparation for washing walls and woodwork before painting, and almost everything about the name is misleading. It contains no sugar: the traditional preparation was an alkaline mixture — sodium carbonate and sodium phosphate with a soap — supplied as crystals that resembled sugar. Modern products vary widely and many contain no soap either, being straightforward alkaline detergent formulations. What they share is the function: an alkaline solution that saponifies greasy films, removes nicotine and cooking residues, and slightly keys the surface so that paint adheres. The nearest single substance here is trisodium phosphate, which a regulator lists as water softener, detergent ingredient and paint remover in one sentence. The consequences follow from the alkalinity rather than the brand. It attacks aluminium, zinc and galvanised metal. It strips oil and wax finishes from timber by design. It leaves an alkaline residue, so the rinse is part of the job — paint over unrinsed residue can fail to adhere. Phosphate content is restricted in many countries, so what is sold under the name varies by market.
Properties
- pH
- Strongly alkaline
What works
Sugar soap is effective against Grease Supported
Why
- Sugar soap is explained by Saponification
- Sugar soap is explained by pH in cleaning
- Sugar soap is explained by Alkali attack on light metals
Sources for this page
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate is used as a water softener, in detergents and as a paint remover, that its solutions react with aluminium, zinc and galvanised iron, and that caustic solutions may be formed on contact with water. (states this directly)
How to Clean Newly Painted Walls
The Sherwin-Williams Company · Manufacturer documentation
Relied on for: That surfaces are cleaned before painting and that what a painted surface tolerates depends on its finish. (states this directly)