“APGs are fine, but they foam far too much for machine applications.” This is a comment we still hear regularly, and one that deserves some nuance: it really depends on the chain length. Alkyl polyglucosides form a broader family than is often assumed, and the short cuts behave in the opposite way to what their general reputation suggests.
Why alkyl polyglucosides hold where ethoxylates give way
In a fatty alcohol ethoxylate, hydrophilicity is carried by the polyoxyethylene chain, whose solvation relies on the hydrogen bonds it forms with water. When temperature or ionic strength rise — caustic soda, potash, silicates, sequestrants — those bonds break: the surfactant dehydrates, the solution turns cloudy, and performance suffers. That is the cloud point, and it is the classic limitation of this family in concentrated alkaline cleaning.
The polar head of an alkyl polyglucoside is of a different nature. The glucoside unit carries several hydroxyl groups whose hydration is far less dependent on temperature. There is therefore no cloud point in the conventional sense, and behaviour in highly alkaline concentrates is markedly better. This explains their growing presence in alkaline degreasers, caustic cleaners and silicate-loaded formulations.
Foam is a question of chain length, not of chemical family
On C8-10 cuts, initial Ross-Miles foam in hard water comes out at around 160 mm. This is an asset in manual and foam-applied cleaning, where foam carries the product on vertical surfaces and makes the application visible. It obviously becomes a constraint in machine washing, clean-in-place or automatic dishwashing. This is precisely where the short cuts change the picture.
Hexyl glucoside (C6)
At 75 % active matter and 100 % bio-based, it offers a strong hydrotropic effect, low foaming and very good solubility in concentrated caustic. It acts as a solubiliser in heavily loaded alkaline formulations whose clarity has to be maintained: returnable bottle washing, metal cleaning, concentrated detergents.
2-ethylhexyl glucoside (C8)
At 65-70 % active matter, with biodegradation measured at 78 % after 28 days, it is low foaming and alkali stable. It brings wetting, degreasing and dispersion, with a genuine foam-inhibiting effect. This is the cut to consider for clean-in-place, caustic cleaners or automatic dishwashing.
C8-10 cuts and above
These remain the core of the range in manual applications and in cosmetics, with an abundant foam profile, good mildness and a recognised compatibility with anionic surfactants, whose foam they boost. Lauryl glucoside and coco glucoside naturally occupy this ground.
A few performance benchmarks
| Cut | Dominant function | Foam | Typical applications |
|---|---|---|---|
| C6 — hexyl glucoside | Hydrotrope, solubiliser | Very low | Alkaline concentrates, bottle washing, metal cleaning |
| C8 — 2-ethylhexyl glucoside | Wetting, degreasing, foam inhibitor | Low | CIP, caustic cleaners, automatic dishwashing |
| C8-10 — caprylyl/capryl glucoside | Wetting and detergency, HLB 13-14 | High | All-purpose cleaners, foam application, cosmetics |
| C12-14 — lauryl glucoside | Detergency, foaming power | High | Hand dishwashing, shampoos, shower gels |
On the C8-10 cut, surface tension is brought down to 28-29 mN/m at 1000 ppm, with a wetting time of 45 to 65 s depending on grade and biodegradation above 60 % after 28 days. These are typical values and of course need to be confirmed on the actual formulation.
Two limitations worth knowing
The acetal linkage of alkyl polyglucosides hydrolyses in strong acid, particularly when hot. In a concentrated acid descaler, this is probably not the right choice — unlike ethoxylates, which are quite at ease there. A supplier presenting APGs as a universal solution is not doing you a favour.
Against hypochlorite, they are considerably more tolerant than ethoxylates, which oxidise. Considerably more tolerant does not mean inert, however: at high temperature and high pH, stability has to be validated on the actual formulation and over time.
Combining with other families
Where the foam constraint cannot be resolved by chain length alone, pairing with a silicone defoamer remains the simplest route: a ready-to-use emulsion in liquid media, a granulate on a carrier in powder detergents.
In practice
If you are facing a difficulty with the clarity of an alkaline concentrate, or with a foam profile in a machine, please feel free to tell us about it. In most cases chain length provides a good part of the answer, and we can make a sample available for trial.