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Surfactant system selection: charge class, foam and the viscosity route

A cleansing system is decided by four things: whether a sulfate-free specification applies, where the viscosity is going to come from, what foam character the format needs, and what pH the product will hold. This page sets out what each class is by chemistry and what it constrains — not which one is gentler, and not at what level to use it.

The short answer

A sulfate-free specification removes laureth sulfate and lauryl sulfate by chemistry — and with them the electrolyte viscosity lever that an anionic/amphoteric system relies on. That is the real cost of the switch: the anionic function moves to an isethionate or a sulfosuccinate, the body usually has to come from a polymer, and the pH of a glucoside system has to be brought down, which then changes the preservation window.

Nothing here is a mildness, irritation, safety or hypoallergenic claim. Class chemistry does not establish how a finished product behaves on skin or eyes — that is established by your own testing programme and by the claim substantiation your market requires.

Step 1 · The four questions that decide the structure

Answer them in this order. Only the first one removes classes outright.

1. Is a sulfate-free specification in play?
This is a chemistry question with a definite answer, and it is the only axis on this page that removes classes outright.
- No sulfate restriction
  The anionic-plus-amphoteric structure with an electrolyte viscosity lever remains available.
  Classes in scope: Laureth sulfate (SLES 70%) · Sodium lauryl sulfate (SLS) · Cocamidopropyl betaine (CAPB)
- Sulfate-free required
  Laureth sulfate and lauryl sulfate are excluded by chemistry. The remaining anionic function is normally carried by an isethionate or a sulfosuccinate, with glucosides and an amphoteric.
  Classes in scope: Sodium cocoyl isethionate (SCI) · Disodium laureth sulfosuccinate · Alkyl polyglucosides — coco, decyl, lauryl glucoside · Cocamidopropyl betaine (CAPB)
2. Where will the viscosity come from?
The electrolyte lever only exists in systems that respond to it. A sulfate-free non-ionic system usually needs a polymer instead, which is a different formulation and a different cost structure.
- Electrolyte (salt curve)
  Applies to anionic/amphoteric systems. Viscosity rises to a maximum then falls; the curve has to be mapped for each formula.
  Classes in scope: Laureth sulfate (SLES 70%) · Cocamidopropyl betaine (CAPB)
- Polymer or cellulosic
  Used where the surfactant system does not respond to salt. Clarity, flow behaviour and pH sensitivity become the selection points.
  Classes in scope: Alkyl polyglucosides — coco, decyl, lauryl glucoside · Disodium laureth sulfosuccinate
- Solid / bar format
  Body comes from the solid base rather than from solution rheology.
  Classes in scope: Sodium cocoyl isethionate (SCI)
3. What foam character does the format need?
Foam volume, speed and density are different properties. They are measured, not assumed from a class name.
- High volume, fast
  Traditionally the territory of the sulfate primaries with an amphoteric partner.
  Classes in scope: Laureth sulfate (SLES 70%) · Sodium lauryl sulfate (SLS) · Cocamidopropyl betaine (CAPB)
- Dense and creamy
  Associated with isethionate-based structures; usually a solid or a syndet format.
  Classes in scope: Sodium cocoyl isethionate (SCI)
- Moderate, sulfate-free
  Glucoside and sulfosuccinate structures; foam is normally rebuilt with a boosting co-surfactant rather than matched directly.
  Classes in scope: Alkyl polyglucosides — coco, decyl, lauryl glucoside · Disodium laureth sulfosuccinate · Cocamidopropyl betaine (CAPB)
4. What pH will the finished product hold?
pH decides amphoteric behaviour, sulfosuccinate stability and whether a weak-acid preservation route still has a window. It links this decision directly to the preservative system.
- Acidic, around pH 5
  Common for skin and hair cleansing. Glucoside systems need adjusting down to reach it.
  Classes in scope: Laureth sulfate (SLES 70%) · Cocamidopropyl betaine (CAPB) · Alkyl polyglucosides — coco, decyl, lauryl glucoside
- Near neutral or above
  Changes amphoteric contribution and narrows the weak-acid preservation window — work that through the preservative selector.
  Classes in scope: Alkyl polyglucosides — coco, decyl, lauryl glucoside · Sodium cocoyl isethionate (SCI)
5. Does anything have to deposit from the rinse-off?
Deposition is a polymer question layered onto the surfactant blend, not a property of the cleansing surfactant.
- No deposition requirement
  The blend is designed for cleansing, foam and viscosity only.
- Conditioning deposition required
  A cationic polymer is normally added and interacts with the anionic surfactant. Haze and after-feel become test points.
  Classes in scope: Cationic guar (guar hydroxypropyltrimonium chloride)

Step 2 · What each class is, by chemistry

Charge, role, supply form and electrolyte response are factual properties. None of them is a performance or skin-response claim.

Cosmetic surfactant classes by charge, role, sulfate status and electrolyte response
Class	Charge	Role	Sulfate?	Electrolyte
Laureth sulfate (SLES 70%)	Anionic	primary	Yes	Responds to electrolyte
Sodium lauryl sulfate (SLS)	Anionic	primary	Yes	Limited electrolyte response
Cocamidopropyl betaine (CAPB)	Amphoteric	secondary	No	Responds to electrolyte
Alkyl polyglucosides — coco, decyl, lauryl glucoside	Non-ionic	co-surfactant	No	Limited electrolyte response
Sodium cocoyl isethionate (SCI)	Anionic	primary	No	Electrolyte lever not applicable
Disodium laureth sulfosuccinate	Anionic	co-surfactant	No	Limited electrolyte response
Alkanolamides — cocamide DEA / MEA	Non-ionic	additive	No	Limited electrolyte response
Cationic guar (guar hydroxypropyltrimonium chloride)	Cationic polymer	additive	No	Electrolyte lever not applicable

"Sulfate?" is a statement about the chemistry of the class, not about how a finished product behaves and not about claim eligibility.

Step 3 · What each class constrains

These are the formulation and documentation consequences that decide whether a class fits the brief.

Laureth sulfate (SLES 70%)
Anionic · 70% paste — dilution and handling are part of the process design
- · The reference primary surfactant for foam volume and cost-in-use in rinse-off systems.
- · Viscosity is normally built with an electrolyte together with an amphoteric partner; the response is the salt curve.
- · Excluded by definition where the customer specification says sulfate-free.
Watch-outs
- · A 70% paste is not a 70% active blend in the finished product — check the active matter on the certificate of analysis for the exact grade.
- · Salt additions have a maximum on the curve; beyond it viscosity falls again.
SLES 70%
Sodium lauryl sulfate (SLS)
Anionic · Needle, powder or solution depending on grade
- · High foam volume and rapid wetting; widely used in cleansing and in technical applications.
- · Different salt-curve and solubility behaviour from laureth sulfate — the two are not drop-in substitutes.
Watch-outs
- · Cold-temperature solubility and clarity differ from SLES; check at your lowest storage temperature.
- · Excluded where a sulfate-free specification applies.
Sodium Lauryl Sulfate (SLS)
Cocamidopropyl betaine (CAPB)
Amphoteric · Typically ~30% active solution
- · Used as the standard partner to an anionic primary; the pair is what builds viscosity with electrolyte.
- · Behaves differently above and below its isoelectric region, so system pH changes what it contributes.
- · Present in both sulfate and sulfate-free structures.
Watch-outs
- · Grade quality varies; residual amidoamine and monochloroacetate are specification points to request.
- · It is a partner, not a primary — a system built on betaine alone behaves differently in foam and viscosity.
Cocamidopropyl Betaine (CAPB)
Alkyl polyglucosides — coco, decyl, lauryl glucoside
Non-ionic · ~50% active solutions; alkaline as supplied
- · The usual route where a sulfate-free structure is specified.
- · Non-ionic, so the electrolyte lever that works on an anionic/amphoteric pair largely does not apply.
- · Chain length differs between coco, decyl and lauryl grades and changes foam character and solubility.
Watch-outs
- · Supplied alkaline; the finished product usually needs acid adjustment, which then interacts with the preservation route.
- · Viscosity normally has to come from a polymer or a structuring co-surfactant rather than from salt.
Decyl Glucoside
Sodium cocoyl isethionate (SCI)
Anionic · Solid — noodles, flakes or powder
- · Anionic but not a sulfate, which is why it appears in sulfate-free bar and syndet structures.
- · Dense creamy foam character; commonly combined with a co-surfactant for solubility.
- · Solid supply form makes it the usual base for syndet bars and powder-to-foam formats.
Watch-outs
- · Dissolution needs heat and time; incomplete dissolution is felt as grit in a liquid system.
- · Solubility in cold water is limited — this drives the format decision more than any other property.
Sodium Cocoyl Isethionate (SCI)
Disodium laureth sulfosuccinate
Anionic · Typically ~30–40% active solution
- · Anionic and sulfate-free; used to carry part of the anionic function in a sulfate-free structure.
- · Often combined with an amphoteric and a glucoside rather than used alone.
Watch-outs
- · Hydrolysis behaviour is pH-dependent; hold the system in the range the supplier's technical literature states for that grade.
- · Foam and viscosity contribution differ from a laureth sulfate — the structure has to be rebuilt, not substituted.
Disodium Laureth Sulfosuccinate
Alkanolamides — cocamide DEA / MEA
Non-ionic · Liquid (DEA) or flake (MEA)
- · Traditional foam and viscosity aids in anionic systems.
- · MEA is a flake and needs melting or hot addition; DEA is a liquid.
Watch-outs
- · Some customer and retailer specifications restrict alkanolamides — confirm the specification before designing them in.
- · Check the Health Canada Cosmetic Ingredient Hotlist entry and your customer's restricted-substance list for the specific material.
Cocamide DEA
Cationic guar (guar hydroxypropyltrimonium chloride)
Cationic polymer · Powder, dispersed in the water phase
- · Not a cleansing surfactant. It is a cationic polymer used in surfactant systems for deposition and for body.
- · Interacts with the anionic surfactant, which is the mechanism behind the deposition behaviour.
Watch-outs
- · Hydration is pH-dependent; it is normally dispersed and hydrated before the surfactants are added.
- · Over-addition can produce haze or a coated after-feel — investigate against a control.
Guar Hydroxypropyltrimonium Chloride

Step 4 · The sulfate-free rebuild, stated plainly

What is removed by chemistry, and what has to be rebuilt as a consequence.

Removed by chemistry

· Laureth sulfate (SLES 70%)
· Sodium lauryl sulfate (SLS)

Still available

· Cocamidopropyl betaine (CAPB)
· Alkyl polyglucosides — coco, decyl, lauryl glucoside
· Sodium cocoyl isethionate (SCI)
· Disodium laureth sulfosuccinate
· Alkanolamides — cocamide DEA / MEA
· Cationic guar (guar hydroxypropyltrimonium chloride)

· The electrolyte viscosity lever largely goes with the sulfates. Budget for a polymer or a structuring co-surfactant instead of assuming salt will thicken the new system.
· Glucosides are supplied alkaline. Bringing the product back to an acidic pH is part of the rebuild, and it changes which preservation route still has a window.
· Active matter differs between a 70% paste, a 30% solution and a solid. Compare formulas on active contribution, not on percentage added.

What you still have to establish

Confirm foam, viscosity, clarity, pH and cold-stability on the finished formula. A surfactant blend that works at one active-matter level and one pH will not necessarily behave the same at another.

No blend ratio or use level is given for your formula. Active-matter contribution differs by grade and by supply form, so every structure below has to be built and measured on your own bench.

Use this when

A customer specification says sulfate-free and you need to know what that removes and what it forces you to rebuild.
A system will not thicken and you need to know whether the electrolyte lever exists in that chemistry at all.
You are comparing an isethionate, a sulfosuccinate and a glucoside route for the same brief.
You need to write a raw-material specification that survives a supplier change.

How this decision is structured

Classes are described by charge, role, supply form and salt-curve response — all factual properties, not performance verdicts.
The sulfate-free axis is treated as a chemistry fact, and it is the only axis that removes classes outright.
Viscosity route is treated as a separate decision from foam, because the two are commonly conflated.
pH is carried through to the preservation decision instead of being answered twice.
Deposition is treated as a cationic-polymer layer on top of the blend, not as a surfactant property.

What this page does not determine

It does not state that any class is mild, gentle, non-irritating or hypoallergenic. Mildness of a finished product is established by your own testing and substantiation, never by a class name.
It gives no blend ratio and no use level. Active matter differs by grade and by supply form.
It does not establish claim eligibility. A sulfate-free structure is a chemistry statement, not a marketing or regulatory approval.
It does not establish permitted use in Canada — that is a Cosmetic Ingredient Hotlist question for the specific substance and product type.
It does not predict foam volume, clarity or viscosity in your formula. Those are measured.

Relevant Allzone products

These are catalogue identities relevant to this decision. A listing here is not a statement that the material is suitable for your formula, and it is not a permitted-use, safety or performance claim.

Ask for a quotation or a specification

Where this comes from, and what it cannot tell you

Published surfactant science (charge classes, micellisation, electrolyte response of anionic/amphoteric systems)
Supports: That surfactants are classified by charge, that anionic and amphoteric blends respond to added electrolyte with a viscosity maximum, and that non-ionic alkyl polyglucoside systems largely do not respond to that lever.
Limitation: Charge class predicts formulation behaviour, not skin or eye response and not finished-product performance. The salt curve must be mapped for each formula.
Universal · Established surfactant chemistry; confirm grade behaviour on the data sheet.
INCI nomenclature and the supplier certificate of analysis for the specific grade
Supports: That an INCI name identifies a substance but not its grade, active matter, supply form or impurity profile — those come from the certificate of analysis and the technical data sheet.
Limitation: Two materials sharing an INCI name can differ in active matter and behaviour. Nothing here substitutes for the documentation of the lot you buy.
International · Request current documentation for each lot.
Health Canada — Cosmetic Ingredient Hotlist
Supports: That restricted and prohibited substances in cosmetics sold in Canada are defined by the Hotlist, and that the Hotlist entry — not this page — is the authority for any concentration limit or labelling condition.
Limitation: The Hotlist states restrictions. It never states that an unrestricted ingredient is effective, safe in your formula, or approved for your product.
Canada · Consult the current published Hotlist before every formulation decision.
Published cosmetic stability-testing practice (accelerated, room-temperature, cycling and freeze–thaw protocols)
Supports: That physical stability is established by a defined stability programme on the finished product in its final packaging, including accelerated and real-time storage.
Limitation: Accelerated storage is an indicator, not a prediction. An accelerated result does not establish real-time shelf life, and a passed protocol applies only to the formula, batch and pack tested.
International · Follow the protocol your own quality system defines.