The HLB Scale: A formulador's Guide to emulsificante Selection

Qué es HLB?

HLB is a relative scale from 0 (fully lipophilic) to 20 (fully hydrophilic). no iónico tensioactivos with long óxido de etileno chains sit at the high end; sorbitan monoesters with little or no EO sit at the low end. The number represents the balance between the hydrophilic and lipophilic portions of the molecule and correlates with the type of emulsion a tensioactivo will favour.

Griffin's original method calculates HLB for etoxilatod no iónicos from molecular weight ratios. In practice, formuladores use published HLB values for commercial grades and blend two or more emulsificantes to achieve a target system HLB.

Required HLB: matching emulsificantes to the oil phase

Each oil, wax, or lipophilic active has a required HLB — the system HLB at which it is most easily emulsified in an O/W system. When the emulsificante system HLB matches the required HLB of the oil phase, emulsions form more readily and tend to be more stable. Required HLB is determined experimentally and published in Formulación handbooks; values below are representative guides.

Calculating blend HLB

When blending two or more emulsificantes, system HLB is the weighted average:

System HLB = (fraction A × HLB A) + (fraction B × HLB B) + …

Example: 70% Polysorbate 60 (HLB 14.9) + 30% Sorbitan stearate (HLB 4.7) gives 0.7 × 14.9 + 0.3 × 4.7 = 10.4 + 1.4 = 11.8. This is close to the required HLB of mineral oil (10–11) and suitable for an O/W cream containing mineral oil in the oil phase.

Worked example 1: O/W hand cream

Formula target: 15% oil phase (cetyl alcohol + mineral oil), O/W emulsion, stable at 40°C storage.

Step 1: Calculate weighted required HLB of oil phase. Mineral oil (required HLB ~10.5) at 10% plus cetyl alcohol (required HLB ~15) at 5% gives weighted required HLB ≈ 11.

Step 2: Blend emulsificantes to system HLB 11 — e.g. 70% Polysorbate 60 (HLB 14.9) + 30% Sorbitan stearate (HLB 4.7) → calculated system HLB ≈ 11.8.

Step 3: Use 4–5% total emulsificante on formula weight. Heat aceite y agua phases separately to 75°C, combine with homogenization, and cool with gentle stirring.

Step 4: Adjust viscosity with 0.1–0.3% electrolyte or 0.5% xanthan gum if needed. Run 40°C / 75% RH estabilidad for 4 weeks minimum.

Worked example 2: agroquímico EC dilution

An emulsifiable concentrate containing 50% actives in aromatic solvent must disperse into hard water at 1:500 dilution without creaming or oil separation.

• Target emulsificante system HLB 10–12 for the solvent/actives blend.
• Blend calcium dodecylbenzene sulfonate (hydrotrope/wetting aid) with C9–C11 alcohol etoxilato (5 EO) at approximately 1:1 ratio.
• Total emulsificante package typically 8–15% of the EC formula.
• Test CIPAC 36.1 dilution estabilidad at 0°C, 20°C, and 54°C before registration.

See also our emulsifiable concentrates guide for EC Formulación principles.

Worked example 3: Fragrance solubilization

To clear-solubilize 1% perfume oil in an aqueous toner without cloudiness:

• Use Polysorbate 20 (HLB ~16.7) at a minimum 3:1 tensioactivo-to-oil ratio — i.e. 3% PS 20 for 1% fragrance.
• Pre-mix fragrance with polysorbate before adding to water.
• Increase ratio to 4:1 or 5:1 for difficult terpene-rich or resinous oils.
• If clarity is marginal, add 0.5–1% ethanol as co-solvent.

HLB for W/O emulsions

W/O emulsions require low-HLB emulsificantes in the 3–6 range. A water-in-mineral-oil Formulación might use sorbitan oleate (HLB ~4.3) or glycerol monooleate (HLB ~3.8) as the primary emulsificante, possibly with a low-EO alcohol graso etoxilato as co-emulsificante. The required HLB concept still applies but targets the W/O side of the scale.

History and development of the HLB concept

The HLB system was introduced in 1949 by William C. Griffin, a chemist working at Atlas Powder Company (later absorbed into ICI Americas), who needed a systematic way to rank the growing number of sorbitan-ester and polysorbate emulsificantes the company was commercializing. Griffin's original paper, published in the Journal of the Society of Cosmetic Chemists, proposed a simple arithmetic method: for Ácido graso esters, HLB = 20 × (1 − S/A), where S is the saponification number of the ester and A is the acid number of the Ácido graso. For tensioactivos where saponification is not straightforward, Griffin offered an alternative based on the weight percentage of the hydrophilic portion of the molecule divided by five, capping the practical scale at 20.

In 1957, Australian chemist Norman Davies extended the concept with a group-contribution method that assigns numerical values to specific chemical groups — sulfate, carboxylate, ether oxygen, hydroxyl — and sums them to estimate HLB directly from molecular structure. The Davies method was a significant advance because it could be applied to ionic tensioactivos that Griffin's original saponification approach could not handle well, broadening HLB's usefulness beyond the no iónico esters it was originally designed for.

A related but distinct approach is the phase inversion temperature (PIT) method developed by Kozo Shinoda in the 1960s. Rather than assigning a fixed number to a tensioactivo, PIT identifies the temperature at which an O/W emulsion inverts to W/O as the no iónico emulsificante's hydrophilicity decreases with rising temperature. PIT-based Formulación is ampliamente utilizados alongside HLB in cosmetic and industrial emulsion design, particularly for systems stabilized by etoxilatod no iónicos whose solubility is strongly temperature-dependent. Modern formuladores often combine HLB for initial emulsificante screening with PIT or direct estabilidad testing for final optimization, since no single number fully captures real-world emulsion behaviour.

Limitations and practical tips

HLB is a starting point, not a guarantee of emulsion estabilidad. Real-world behaviour is also affected by:

• Temperature — punto de turbidez and emulsion viscosity change with temperature; a stable room-temperature emulsion may separate at 40°C.
• Electrolytes — salts compress the electrical double layer and can break O/W emulsions or invert them.
• pH — ionic emulsificantes change charge state; ester-based emulsificantes may hydrolyse at extreme pH.
• Co-tensioactivos and thickeners — alcoholes grasos, waxes, and polymers build viscosity and gel network estabilidad beyond what HLB alone predicts.
• Phase volume ratio — high internal phase emulsions need more emulsificante than dilute systems.

Always validate with accelerated estabilidad testing and application-specific Rendimiento tests. For complex systems, Venus technical support can recommend alcohol graso etoxilatos, polysorbates, and custom emulsificante blends. Read tensioactivo vs emulsificante for context on when HLB applies. Contacte con Venus for samples and HLB matching support.