Poor young Beervater, who we lost to covid, would have found this interesting:

Why the foam on Belgian beers lasts so long

https://phys.org/news/2025-08-foam-belgian-beers.html

In this study, the materials scientists showed that Belgian beers that have been triple fermented have the most stable foam, followed by double fermented beers. The head is least stable in single fermented lager beers.

Triple-fermented beers include Trappist beers, a specialty of the eponymous monastic order. A beer from a large Swiss brewery was also among the lager beers the ETH researchers examined. “There is still room for improvement—we are happy to help,” says Vermant.

To date, researchers assumed that the stability of beer foam depended primarily on protein-rich layers on the surface of the bubbles (see ETH News): proteins come from barley malt and influence surface viscosity, i.e. the stickiness of the surface, and the surface tension.

Surface stress instead of viscosity

The new experiments, however, show that the decisive mechanism is more complex and depends significantly on the type of beer. In single-fermentation lager beers, surface viscosity is the decisive factor. This is influenced by the proteins present in the beer: the more proteins the beer contains, the more viscous the film around the bubbles becomes and the more stable the foam will be.

More at link.