Short answer: For standard laundry powders in soft-to-medium water, SLS 92% is the lowest-cost primary surfactant. For hard-water markets, powders switch to AOS 92% or 95%. For liquids, SLES 70% is the practical base because it dissolves easily and thickens with salt, with AOS 38% as the hard-water and sulfate-free option. Typical surfactant levels are roughly 10–20% in standard powders and 10–30% active in liquids, depending on format and market — always confirmed in your own trials.
This guide is for formulators and product managers choosing the primary anionic surfactant for a detergent, and for buyers who need to understand why the specification on the purchase order looks the way it does. It covers powders and liquids separately, because the constraints are different.
Key takeaways
- Powders: choose between SLS 92/95% and AOS 92/95% on water hardness and cost.
- Liquids: choose between SLES 70% and AOS 35/38% on mildness, thickening behaviour and hardness tolerance.
- Water hardness is the single biggest technical switch: soft water favours SLS, hard water favours AOS.
- Salt (NaCl) thickening works with ether sulfates such as SLES; it does very little with SLS alone.
- Compare candidates on cost per kilogram of active matter, then validate in a trial — formulation performance is not visible on a COA.
What the primary surfactant actually does
In a detergent the primary surfactant carries three jobs: it lowers surface tension so water wets the surface, it lifts and emulsifies oily soil, and it produces the foam that consumers read as cleaning power. Secondary surfactants, builders, enzymes and polymers then fine-tune performance. The choice of primary sets the cost floor and the foam profile, so it is the decision that everything else is built around.
Powder detergents
SLS 92% — the default for cost-driven powders
Sodium lauryl sulfate (SLS CAS 151-21-3) at 92% active is the workhorse of laundry powders. It gives high flash foam, strong detergency and the lowest cost per kilogram of active matter, and it is available as powder and needles so it can be matched to your agglomeration or spray-drying line — see SLS needles vs powder for the handling differences.
Two limits to design around: performance drops in very hard water unless the formula carries enough builders or chelants, and solutions cloud at low temperature. If your market has hard water, read the next section before committing.
AOS 92% and 95% — the hard-water choice
Sodium C14-16 olefin sulfonate (AOS CAS 68439-57-6) keeps foam and detergency where sulfate esters lose efficiency, because the sulfonate group is not affected by calcium and magnesium in the same way. It is also stable across a wider pH range. Powder grades are typically 92% and 95%; the trade-offs are covered in the AOS buyer’s guide. Our FAQ on SLS in hard water explains the mechanism in plain terms.
Choosing between grades within the same chemistry
Moving from 92% to 95% active buys about three percentage points more functional surfactant per kilogram plus a cleaner impurity profile — less unsulfated alcohol, less salt and better colour. Detergent powders rarely need it; oral care and premium personal care usually do. The full comparison is in SLS 92% vs 93% vs 94% vs 95%.
Liquid detergents
SLES 70% — the standard liquid base
Sodium laureth sulfate (SLES CAS 68585-34-2) at 70% active is the base of most hand dishwashing liquids, shampoos and body washes. It is mild, tolerant of electrolytes, easy to pump as a paste, and — critically — it thickens with sodium chloride, which is how most liquid detergents reach their target viscosity cheaply. Specification and packaging details are in the SLES 70% buyer’s guide.
AOS 35% and 38% — hard water and sulfate-free positioning
Liquid AOS is used where the market has hard water or where a sulfate-free claim is part of the product positioning, since AOS contains no sulfate ester group. It foams quickly and cleans well, but its thickening response differs from SLES, so viscosity building usually needs a different approach.
Where SLS 30% liquid fits
SLS 30% solution is used when a plant wants SLS chemistry without handling powder — no dust, no dissolution step. It is more expensive to import because most of the shipment is water, so it is normally a regional product bought close to the factory. Use the landed-cost method in our guide to comparing surfactant quotes to check the economics.
Selection table
| Product | Water hardness | Recommended primary surfactant | Typical inclusion level (active) | Notes |
|---|---|---|---|---|
| Standard laundry powder | Soft to medium | SLS 92% powder or needles | ≈ 10–20% | Lowest cost per kg active; high flash foam |
| Laundry powder, hard-water market | Hard | AOS 92% or 95% powder | ≈ 10–20% | Foam and detergency hold without heavy builder loading |
| Compact or tablet powder | Any | AOS 95% or SLS 95% | Higher than standard | Higher active helps where dose volume is limited |
| Hand dishwashing liquid | Medium to hard | SLES 70%, optionally with AOS 38% | ≈ 10–30% total active | Salt thickening; AOS added for hardness tolerance |
| Laundry liquid | Medium | SLES 70% with nonionic co-surfactant | ≈ 10–25% | Balance detergency and low-temperature stability |
| “Sulfate-free” liquid | Any | AOS 35% or 38% | ≈ 10–25% | Sulfonate chemistry; verify claim with regulatory team |
| Industrial cleaner | Any | SLS 92% or 30% liquid | Application-specific | Cost-driven; high alkalinity tolerance needed |
Inclusion levels above are typical formulation ranges, not recommendations. Your builder system, enzymes, target foam profile and local cost pressure all shift them.
From selection to purchase order
- Pick the chemistry from the table, then pick the grade on water hardness, claim strategy and cost target.
- Ask for the TDS and the COA from a recent lot, and check the parameters in how to read a COA.
- Order a laboratory sample and run your own formulation trial, including a stability check at the lowest and highest storage temperatures you expect.
- Confirm packaging against your plant: bag size and liner for powders, drums or IBCs for liquids — see export packaging options.
- Agree the specification windows you actually need, and confirm change control in writing.
Frequently asked questions
Which is better for laundry powder, SLS or AOS?
In soft to medium water, SLS 92% is usually cheaper per kilogram of active matter and performs well. In hard water, AOS keeps foam and detergency where SLS fades, and it often costs less overall because you can reduce builder loading. Test both in your own formula and local water.
Why does my SLS-based liquid not thicken with salt?
Salt thickening is characteristic of ether sulfates such as SLES. Plain alkyl sulfates like SLS respond far less. To build viscosity in an SLS-based liquid, add an ether sulfate, a betaine or an amide, or move the base to SLES 70%.
Can I use SLS 95% instead of SLS 92% without changing the formula?
You can, but rebalance the dose. The 95% grade carries roughly three percentage points more active matter per kilogram, so dosing by weight will overdose slightly. Most formulators reduce the addition rate and gain a cleaner colour and odour profile.
What surfactant level should a dishwashing liquid start from?
A typical starting point is a total active surfactant level in the low-to-mid twenties as a percentage of the formula, adjusted for foam target, cost and the thickener system. Start from a known benchmark formulation and optimise rather than designing from zero.
Is AOS suitable for a sulfate-free claim?
AOS is an olefin sulfonate with no sulfate ester group, which is why it is widely used in sulfate-free formulations. Claims rules vary by market and retailer, so confirm the wording with your regulatory or marketing team before launch.
Written and reviewed by the ORID Chem technical team. Last updated: 29 September 2026. Inclusion levels are typical formulation ranges for guidance only; validate performance, stability and cost in your own trials before commercialising.
