SLES 70% vs SLES 28%: which grade should you buy?

Buy SLES 70% if you have mixing equipment and want to ship less water. Buy SLES 28% if you want a pourable liquid you can dose straight into a formulation. Both are the same surfactant, sodium laureth sulphate, at different concentrations. The choice comes down to freight cost, equipment and how much handling your plant can take on.

What is SLES?

Sodium laureth sulphate (sodium lauryl ether sulphate) is an anionic surfactant. It is made by ethoxylating lauryl alcohol, usually with an average of two or three moles of ethylene oxide, then sulphating the result and neutralising it with caustic soda. The ether chain makes it milder on skin than sodium lauryl sulphate and gives it good foam and a strong response to thickening with salt.

That combination is why SLES is the base surfactant in most shampoos, body washes, hand washes and dishwashing liquids.

Why is SLES sold at 70% and 28%, and not 50%?

It comes down to how SLES behaves in water. As the concentration rises, the surfactant molecules pack into different structures, and the viscosity changes sharply:

• Below about 30% active, SLES forms an isotropic micellar solution. It is a clear, pourable liquid.
• Between roughly 30% and 60%, it passes through a very stiff gel phase. At these concentrations it is too thick to pump or pour in normal equipment.
• Around 70%, it forms a lamellar phase, a soft paste that flows under shear and can be pumped.

So the market settled on two grades either side of the gel region: a liquid just below it, and a paste above it. A 50% grade would sit in the gel and be almost impossible to handle.

How do the two grades compare?

The freight difference is the main reason 70% exists. To get one tonne of active surfactant you need about 1.43 tonnes of SLES 70% or about 3.57 tonnes of SLES 28%. On long routes, that gap matters.

How should you dilute SLES 70%?

Diluting the paste means passing through the gel region, so the order and method matter.

1. Add the paste to the water, not the water to the paste. Starting with water keeps the mix on the dilute side, and the paste disperses as it goes in.
2. Stir steadily without whipping in air. SLES foams easily, and trapped air is slow to release.
3. Add the paste gradually so lumps have time to dissolve rather than forming a gel skin.
4. Warm water helps, because it speeds dissolution, but follow the supplier's safety data sheet for temperature limits.

If gel lumps do form, more stirring time usually clears them. Pouring water onto a drum of paste is the classic way to end up with a stubborn gel.

What are the handling and storage differences?

Hydrolysis. SLES is a sulphate ester. Under acidic conditions, especially when warm, it can hydrolyse back towards the alcohol ethoxylate and sulphuric acid, which lowers the pH further and speeds the reaction. Keep it near neutral pH and avoid long storage in heat.

Microbial growth. Dilute surfactant solutions are a better home for bacteria than concentrated paste. SLES 28% is therefore more sensitive to contamination, and liquid grades often contain a preservative. Keep containers closed and use them in rotation.

Cold. Both grades thicken in the cold. The paste in particular may need warming before it will pump.

Hazards. Both grades can irritate skin and cause serious eye damage at these concentrations. Use eye protection and gloves when handling, and read the SDS for the specific grade.

Are both grades classified the same way?

Yes. Both are anionic organic surface-active agents and sit in HS subheading 340239, the same as other anionic surfactants such as AOS and SLS. The concentration does not change the subheading, though your documents should state the grade and active content so customs and your QC team know which one arrived.

How do you compare quotes between grades?

Compare on the price of active matter, not the price per kilogram of product. A kilogram of SLES 70% carries two and a half times the surfactant of a kilogram of SLES 28%. Divide the price by the active content, then add freight, packaging and your own cost of dilution (water, energy, labour and mixing time).

Also check what each specification covers. Typical points are active matter, pH, unsulphated matter, sodium sulphate and colour. Ask for an SDS and a certificate of analysis so you are comparing like with like.

How does SLES fit with other surfactants?

SLES is rarely used alone. In dishwashing liquids it is often blended with LAS, made by neutralising LABSA, because the pair foams well and cleans grease at low cost. In personal care it is commonly paired with a mild amphoteric co-surfactant to soften it further. The grade you buy does not change those formulations; it only changes how much water you add on site.

Which one should you choose?

Choose SLES 70% when you run a mixing vessel, buy in volume, or ship over long distances, and you are comfortable with a dilution step. Choose SLES 28% when you make smaller batches, lack dilution equipment, or want to dose the surfactant as received.

Either way, you can request a quote for SLES 70% or SLES 28% and say which packaging suits your plant.