Hydrophilic-lipophilic balance

What is hydrophilic-lipophilic balance?

Hydrophilic-lipophilic balance (HLB) expresses, as a single number, the balance between the water-loving (hydrophilic) and oil-loving (lipophilic) parts of a surfactant molecule. William Griffin introduced the system in 1949 to help chemists choose emulsifiers without testing every candidate by trial and error.

A surfactant with a low HLB is dominated by its oil-loving tail and dissolves or disperses better in oil. A surfactant with a high HLB is dominated by its water-loving head and dissolves better in water. That tendency predicts which kind of emulsion the surfactant will favor and what jobs it suits.

HLB is also the abbreviation for huanglongbing, a disease of citrus trees. The two are unrelated.

How HLB is calculated

Griffin’s method, designed for nonionic surfactants, calculates HLB from the share of the molecule’s mass that is hydrophilic:

HLB = 20 × (molecular mass of the hydrophilic portion ÷ total molecular mass)

The result falls between 0, for a molecule with no hydrophilic part, and 20, for one that is entirely hydrophilic.

Davies’ method, published in 1957, assigns a group number to each chemical group in the molecule, positive for hydrophilic groups and negative for lipophilic ones, and adds them to a base value of 7. It can be applied to ionic surfactants, whose values can exceed 20.

Suppliers often publish HLB values measured or estimated by their own methods, so values for similar products from different sources are best compared with caution.

What HLB values mean

Griffin’s work gave approximate ranges that are still widely used:

HLB range	Typical use
About 1.5 to 3	Antifoaming agents
About 4 to 6	Water-in-oil emulsifiers
About 7 to 9	Wetting agents
About 8 to 18	Oil-in-water emulsifiers
About 13 to 15	Detergents
About 15 to 18	Solubilizers

The ranges overlap, and they are guides rather than rules.

Required HLB and emulsifier blends

Each oil has a required HLB: the HLB of the emulsifier system that produces the most stable emulsion of that oil in a given emulsion type. Formulators often reach the required value by blending two surfactants, one with a low HLB and one with a high HLB. The HLB of a blend is approximately the weighted average of its components, by mass. Blends frequently outperform a single surfactant of the same HLB, because the two molecules pack together more effectively at the droplet surface.

Limits of the HLB system

HLB is a starting point for selecting surfactants, not a prediction of performance. It was developed for nonionic surfactants and is less reliable for ionic ones. It also ignores conditions that change how a surfactant behaves: temperature, salinity, the nature of the oil, and other ingredients. Nonionic surfactants in particular become more oil-loving as temperature rises. More complete frameworks, such as hydrophilic-lipophilic deviation (HLD), account for those variables and are used where conditions vary widely, including surfactant flooding in oil reservoirs.

HLB and Locus biosurfactants

Locus publishes approximate HLB values for its Amphi glycolipid ingredients, describing one grade as relatively hydrophilic, at about HLB 11, and another as relatively hydrophobic, at about HLB 9, so that formulators can choose a grade to suit the system.

Frequently asked questions