Does a thinner formulation mean its network has disappeared?

More material, yet less resistance to flow

In a specific anionic gemini surfactant/CTAB mixture, zero-shear viscosity first increased and then decreased with total concentration. The plateau modulus continued to rise in the declining-viscosity region. This was a mixture, not a pure gemini system or a finished shampoo.

The paired observations make viscosity alone an insufficient basis for declaring that structure has disappeared. We do not use the conflicting low-concentration labels in one paragraph or convert the reported concentrations into a general formulation range.

Flow, frequency response and structure ask different questions

Low-shear viscosity describes resistance to slow flow. A plateau modulus describes an elastic response over a suitable frequency range; a crossover frequency marks where elastic and viscous moduli are equal. They are not interchangeable measures.

At fixed mixture composition and pH, the viscosity decline was accompanied by a continuing plateau-modulus increase and a rising crossover frequency. The authors interpreted the pattern in terms of branched micelles; cryogenic electron microscopy also showed a network with junctions.

This supports an interpretation rather than uniquely proving it. DLS in the study measured an apparent hydrodynamic size. It was not a direct count of branches, and neither a viscosity curve nor a size reading supplies a universal branching index.

A softer formulation can still show a network

A separate supramolecular-shampoo study progressively added ingredients to an SCG gel. The storage modulus decreased overall; the final G8 formulation retained gel-like behaviour, and wet optical microscopy showed a fibrous network.

These observations allow softening and an observable network to coexist. They do not prove that faster relaxation caused the softening. The optical fibres cannot be identified with the branched micelles in the other study.

The sharp modulus reduction reported for SCA after adding CAPB belongs to a different sample series and must not be assigned to the SCG shampoo. The preservative comparison explicitly screened rheological compatibility, not antimicrobial performance.

A useful comparison does not need a universal mechanism

Together, the papers limit the shortcut that thinner or softer means no network. One connects concentration-dependent viscosity with frequency response and microscopy; the other shows formulation softening alongside persistent gel-like behaviour.

They vary different materials and conditions and probe different length scales. They do not rank the stability of two network types or demonstrate a shared causal mechanism.

Muzi would first check dilution, salt, pH and shear history, then combine flow, interpretable frequency response and an independent structural observation. The purpose is to avoid automatically adding more thickener after one viscosity reading.

Choose tests that distinguish the alternatives

These are proposed experiments. If a structure persists but relaxes faster, an interpretable linear frequency spectrum should show corresponding changes while reproducible structural evidence remains. If load-bearing structure is lost or phase separation occurs, independent structural changes should weaken the relaxation-only explanation. Both processes can coexist.

First compare an additive group with a vehicle-, salt- and pH-matched control in one target formulation, holding active surfactant concentration, temperature and shear history fixed. Use strain sweeps to locate the linear region, then measure flow and frequency response across independently prepared batches. Do not force a single-relaxation model if no usable plateau or crossover exists.

Second use separate vehicle, salt and pH controls, changing one factor at a time. Compare viscosity, frequency spectra, turbidity and phase separation. If a matched blank reproduces the change, weaken attribution to a specific additive-induced network rearrangement.

Third choose an independent structural method suited to the relevant scale, with blinded comparison, preparation controls and independent batches. Prespecify interpretable fibre or junction measures where feasible; use DLS only as supporting size information. Inadequate resolution or preparation-induced changes leave the mechanism unresolved.

Fourth retain original-process and untreated-time controls while changing one shear or temperature history at a time. Return samples to identical measurement conditions and compare viscosity, moduli, phase state and recovery. Irreversible changes or poor batch reproducibility weaken a robust-recovery prediction.

A decision can remain unresolved

If only viscosity changes and frequency or structural evidence is inadequate, keep the mechanism open. If structural evidence weakens or phase separation appears, address structure and phase conditions. If a network persists with reproducible relaxation changes, investigate the rearrangement explanation under matched controls.

Similar-looking images do not establish structural equivalence. A nonsignificant result cannot directly refute a difference. Prespecify meaningful effect or equivalence bounds and interpret confidence intervals, detection capability and independent-batch variation together.

This is a diagnostic route, not a universal concentration window, stability ranking, shelf-life claim or evidence of cleansing and mildness.