Four surfactants form the backbone of many cleaning and personal-care formulations: sodium laureth sulfate (SLES), sodium lauryl sulfate (SLS), cocamidopropyl betaine (CAPB) and alkyl polyglucoside (APG). Two are anionic, one is amphoteric and one is nonionic, and they are most often used in combination. Knowing how each behaves on foam, mildness, viscosity and stability makes it much easier to build a system that works, and to write a specification that protects it.
The four at a glance (indicative)
- SLES (sodium laureth sulfate): anionic. Usually supplied as a paste of about 70% active matter (often called SLES 70) or as a liquid of roughly 25–28%, most commonly with an average of two moles of ethylene oxide (2EO). It gives rich foam, thickens well with salt and is milder than SLS. It is the primary surfactant in most shampoos, shower gels and hand dishwashing liquids.
- SLS (sodium lauryl sulfate): anionic. Supplied as powder or needles at typically 90–95% active matter, or as a liquid of about 28–30%. It gives fast, open foam and strong cleaning but is more irritating to skin than SLES. It is common in toothpaste, powder detergents, bath bombs and industrial cleaners.
- CAPB (cocamidopropyl betaine): amphoteric. Usually supplied as a solution of about 30% active matter containing several per cent of sodium chloride from manufacture. As a secondary surfactant it boosts and stabilises foam, reduces the irritation of anionics and helps build viscosity.
- APG (alkyl polyglucoside): nonionic, made from fatty alcohol and glucose. Commonly supplied at around 50–65% active matter, and many grades are supplied at pH 11–12. It is mild and readily biodegradable, and short-chain grades are notably stable in strong alkali and electrolyte, which makes APG a staple of eco-labelled cleaners and sulfate-free personal care.
How they differ in practice
Charge and compatibility. Anionic, amphoteric and nonionic surfactants combine freely, and most commercial systems mix at least two. Anionics are generally incompatible with cationic surfactants and cationic polymers at high concentration, which matters in conditioning products.
Foam. SLS gives the fastest, most open flash foam, and SLES a creamier, denser foam. CAPB stabilises and enriches the foam of anionics rather than foaming strongly on its own. APG foam depends on chain length: C8–10 grades foam modestly and suit low-foam cleaners, while C12–14 grades foam well.
Mildness. SLS is the most irritating of the four, and ethoxylation makes SLES milder. CAPB and APG are milder still and reduce the irritation potential of anionics when blended with them. Two impurities deserve attention: trace 1,4-dioxane, a by-product of ethoxylation, in SLES, and amidoamine and DMAPA, which are known skin sensitisers, in CAPB. Specify low limits for both in personal-care grades.
Viscosity. SLES with CAPB builds viscosity readily with sodium chloride, following a salt curve that peaks and then falls, so add salt in steps. APG-based systems respond poorly to salt and usually need a polymeric thickener.
pH and chemical stability. Alkyl sulfates and ether sulfates can hydrolyse at low pH, especially when warm, so keep acidic formulations of SLES and SLS within the stable range given on the technical data sheet. Short-chain APG remains stable and effective in highly alkaline cleaners containing caustic soda, where most other surfactants struggle.
Typical specification parameters
- Active matter, with the test method stated
- Unsulfated matter or free fatty alcohol (SLES, SLS)
- Sodium sulfate and sodium chloride content
- pH of a stated dilution, and colour
- 1,4-dioxane (SLES), amidoamine and DMAPA (CAPB), and free fatty alcohol (APG)
- Alkyl chain distribution, for example C12–14 or C8–10
- Preservative type and level, and microbiological limits for cosmetic grades
- Feedstock origin: if you need certified palm-derived or palm-free materials, request the certificate scope with your quotation
Choosing a system
- Shampoo and shower gel: SLES as the primary surfactant with CAPB as the secondary, thickened with salt. A common starting point is CAPB at roughly a quarter to a third of the SLES level, adjusted for foam, mildness and viscosity.
- Sulfate-free cleansers: APG with CAPB, or amino-acid surfactants such as sodium lauroyl glutamate and isethionates such as sodium cocoyl isethionate. Our cosmetic and personal care ingredients hub lists the related emulsifiers, humectants and conditioning agents.
- Toothpaste, bath bombs and powder products: sodium lauryl sulfate in powder or needle form blends well with other dry ingredients.
- Hand dishwashing liquid: an anionic base such as SLES, with CAPB or APG to improve mildness and foam stability.
- Industrial alkaline cleaners and clean-in-place (CIP): short-chain alkyl polyglucoside with caustic soda. The detergents and institutional cleaning hub covers the builders and sequestrants, and our caustic soda buyer's guide covers the alkali itself.
Handling notes
SLES 70 paste passes through a very viscous gel phase at intermediate concentrations when it is diluted. Add the paste slowly to water with good agitation, or use a dilution unit, rather than adding water to the paste.
SLS powder and needles produce dust that irritates the eyes and airways. Use local exhaust ventilation and respiratory protection, and treat fine surfactant dust as combustible.
CAPB is a water-based solution that needs preservation, and it should be protected from freezing and stored within the temperature range on the technical data sheet.
APG can become cloudy or separate at low temperatures. Warm it gently and homogenise before use. Because many grades are supplied at high pH, neutralise with an acid such as citric acid during formulation.
In the EU and GB, detergent surfactants must meet the biodegradability requirements of detergents legislation, and cosmetic products must meet the requirements of the cosmetics regulations. Ask for biodegradability data and the relevant regulatory statements with every surfactant you approve.
Frequently asked questions
Is SLES the same as SLS?
No. SLES is ethoxylated before sulfation, which makes it milder, more soluble in cold water and better at building viscosity with salt. SLS is not ethoxylated and gives faster foam, with higher irritation potential.
Why is CAPB used together with SLES?
CAPB improves foam quality and stability, reduces the irritation potential of SLES and helps the system thicken with salt. The combination is a standard base for shampoos and shower gels.
Is APG sulfate-free?
Yes. APG is a nonionic sugar-based surfactant with no sulfate group, so it is widely used in sulfate-free and eco-labelled formulations.
What does SLES 70 mean?
It is SLES paste with about 70% active matter, usually 2EO. Diluted, it gives the same surfactant as liquid SLES at around 25–28%, but it costs less to transport per kilogram of active matter.
Which surfactant works best in strongly alkaline cleaners?
Short-chain APG, typically C8–10, is the usual choice because it stays stable and effective in high concentrations of caustic soda and electrolyte.