HLB in context

HLB and TDA Logic

HLB and its descendants answer the question of which emulsifier, or which conditions, will build a stable emulsion. TDA Logic answers a different question: once a nanoscale structure has been built, where does each added ingredient go, and how much can each part of that structure carry?

Published 6 November 2026 · Primary reference: Pensive Beauty® Nanoscience Labs (2026), Zenodo

Where did HLB come from?

The hydrophile–lipophile balance was introduced by W. C. Griffin, working at the Atlas Powder Company, in a 1949 paper in the Journal of the Society of Cosmetic Chemists [1]. Before it, choosing an emulsifier for a new oil was largely trial and error. Griffin proposed a single number for each nonionic surface-active agent, on a scale running from 0 to 20, describing how strongly the molecule favours water relative to oil. Values of roughly 3 to 6 suit water-in-oil emulsions, roughly 8 to 18 suit oil-in-water emulsions, and the upper end of the scale, from about 15, suits solubilisation.

The idea gave formulators a shared vocabulary and a way to narrow a long list of emulsifiers to a short one. More than seventy years later it still organises how emulsions are taught and designed.

How is an HLB value calculated?

Griffin’s 1949 values were assigned experimentally. In 1954 he published calculation methods for nonionic surfactants [2]. Two are in everyday use:

• Polyhydric alcohol fatty acid esters (for example, glyceryl and sorbitan esters): HLB = 20 (1 − S/A), where S is the saponification number of the ester and A is the acid number of the recovered fatty acid.
• Products whose hydrophile is ethylene oxide alone (for example, fatty alcohol ethoxylates): HLB = E/5, where E is the weight percentage of oxyethylene in the molecule. A molecule that is 60% oxyethylene by weight therefore has an HLB of 12.

Both formulas express the same underlying idea: the share of the molecule’s mass that is hydrophilic, scaled to 20.

What is required HLB, and how does blending work?

Each oil, or oil phase, has a required HLB: the HLB of the emulsifier system at which emulsion stability peaks for a stated emulsion type (oil-in-water or water-in-oil) with that oil. It is found experimentally by emulsifying the oil with a graded series of emulsifier blends and observing where stability peaks. For an oil phase made of several oils, the required HLB is commonly estimated as the weight-averaged value of the components.

Emulsifier blends are handled the same way: the blend’s HLB is taken as the weight-averaged HLB of its components. This additivity is an approximation, but a useful one.

What did Davies, PIT, HLD and Hansen parameters add?

Later frameworks extended Griffin’s idea or answered neighbouring questions.

Davies group contributions (1957)

Davies proposed computing HLB from the structure of the molecule: HLB = 7 + Σ(hydrophilic group numbers) − Σ(lipophilic group numbers), with each –CH₂– or –CH₃ group contributing 0.475 to the lipophilic sum [3]. The method extends HLB to ionic surfactants, which Griffin’s mass-fraction formulas do not cover.

Phase inversion temperature (1964)

Shinoda and Arai showed that an oil-in-water emulsion stabilised by an ethoxylated nonionic inverts to water-in-oil at a characteristic temperature, because the ethylene oxide chains lose hydration as temperature rises, and that this temperature correlates with the surfactant’s cloud point [4]. PIT answered something a single HLB number could not: how the effective balance of a nonionic surfactant moves with temperature. It is used both for selection and for low-energy emulsification.

Hydrophilic–lipophilic deviation (1979)

The HLD approach, which grew from the work of Salager and co-workers on optimum formulation, combines terms for surfactant character, oil type, salinity, temperature and co-surfactant into one expression [5]. HLD = 0 marks the optimum formulation, where interfacial tension is at a minimum; the sign indicates which curvature the surfactant film prefers. HLD generalises HLB and PIT and carries salinity as an explicit term. It remains a tool for choosing surfactants and conditions.

Hansen solubility parameters

Hansen solubility parameters place each material in a three-dimensional space of dispersion, polar and hydrogen-bonding interactions; materials close together in that space tend to be mutually compatible [6]. HSP predicts compatibility and solubility. It does not specify any colloidal structure.

Where does TDA Logic sit among these frameworks?

HLB, Davies, PIT and HLD all help a formulator decide how to build a structure: which emulsifier, at what ratio, under which conditions. TDA Logic starts at a different point. It applies when the colloidal structure is already built and fixed: a nanoscale architecture in which nanocolloidal (oil-core), nanoliposomal (bilayer) and nanomicellar domains are designed to coexist in a continuous water phase under electrostatic (DLVO) stabilisation [8], [9], [10].

On such an architecture the emulsifier decision has been made upstream, so it is no longer a formulation variable. This does not mean the system contains no surface-active material; a lecithin-based architecture contains phospholipids as part of its built structure. It means the formulator is not choosing one. The working questions become: which of the four destinations (water phase, nanomicellar, nanoliposomal or oil-core) does each ingredient belong in, and does the finished formula stay inside the loading limits of each? Ingredients are assigned by polarity at formula pH (logP or logD [7]), solubility and charge, with molecular size as a secondary check. See the placement procedure.

This is why HSP values and logP/logD can serve as inputs to a TDA assignment, while HLB values are not inputs: there is no emulsifier choice for them to inform. Adding further emulsifiers or solubilisers to such a system is generally avoided, because they compete with the interface already built.

What was HLB never designed to tell you?

None of the following is a shortcoming of HLB; these were simply outside the question Griffin set out to answer, which was how to choose an emulsifier for a conventional macro-emulsion.

• Particle size. A well-matched HLB favours a finer emulsion, but droplet size also depends on energy input, process route, concentration and time. The HLB number carries no size term.
• Surface charge. HLB describes the balance between the hydrophilic and lipophilic parts of a surfactant. It has no term for the electrical charge at a droplet surface, which governs electrostatic stabilisation (see colloid science).
• Ingredient location. HLB tells you how to hold the oil phase in water. It does not say whether a given active sits in the oil, at the interface, in micelles or in the water, which is the question that matters once the structure is fixed.
• Ionic strength. Griffin’s number has no salinity term. Electrolytes compress the electrical double layer and can dehydrate surfactant head groups; HLD later added an explicit salinity term to handle part of this.

For a fixed nanoscale architecture, these four properties are the design variables. Because HLB carries no variable for any of them, TDA Logic is proposed as the successor design logic to 1940s HLB logic for formulating on a fixed nanoscale architecture [10]. For building conventional emulsions, HLB and its successors remain the appropriate tools.

References

1. Griffin WC (1949). Classification of surface-active agents by “HLB”. J Soc Cosmet Chem 1:311–326.
2. Griffin WC (1954). Calculation of HLB values of non-ionic surfactants. J Soc Cosmet Chem 5:249–256.
3. Davies JT (1957). A quantitative kinetic theory of emulsion type. I. Physical chemistry of the emulsifying agent. In: Gas/Liquid and Liquid/Liquid Interface, Proc. 2nd Int. Congress of Surface Activity, pp. 426–438. Butterworths.
4. Shinoda K, Arai H (1964). The correlation between phase inversion temperature in emulsion and cloud point in solution of nonionic emulsifier. J Phys Chem 68(12):3485–3490.
5. Salager J-L, Morgan JC, Schechter RS, Wade WH, Vasquez E (1979). Optimum formulation of surfactant/water/oil systems for minimum interfacial tension or phase behavior. SPE J 19(2):107–115. doi:10.2118/7054-PA
6. Hansen CM (2007). Hansen Solubility Parameters: A User’s Handbook, 2nd ed. CRC Press.
7. Leo A, Hansch C, Elkins D (1971). Partition coefficients and their uses. Chem Rev 71(6):525–616. doi:10.1021/cr60274a001
8. Derjaguin B, Landau L (1941). Theory of the stability of strongly charged lyophobic sols and of the adhesion of strongly charged particles in solutions of electrolytes. Acta Physicochimica URSS 14:633–662.
9. Verwey EJW, Overbeek JThG (1948). Theory of the Stability of Lyophobic Colloids. Elsevier.
10. Pensive Beauty® Nanoscience Labs (2026). TDA Logic: The Tri-Domain Placement Logic Succeeding 1940s HLB Logic in Nanoscale Cosmetic Formulation (Version 1.0) [Preprint]. Zenodo. doi:10.5281/zenodo.23384911