Just what is that thin smattering of foam that sticks to the inside of the beer glass after the head has fallen and you’ve drank some of the beer down? It’s called lacing, and there are a wide variety of factors that contribute to its appearance and nature – but lacing is not a direct indicator of beer quality.
To clarify, the head of the beer is the fluffy foam at the very top of the beer and the lacing is the leftover white/cream that clings to the glass at every point where the head comes to sit as you deplete your beer. It’s made up of a protein structure, as is the head, which is why it can sometimes be quite tall and stiff, depending on how much protein is hanging out with the CO2. This protein, LTP1, is hydrophobic (it avoids contact with water if at all possible) forms a coating around a bubble and helps head keep its structure this way. More on this later.
Some of the things that influence beer lacing are:
- cleanliness of the glass
- dryness of the glass
- malt levels
- hop levels
- freshness of hops
- alcohol content
- amount of carbonation
- type of carbonation
- and more!
A clean glass with no soap residue promotes lacing (if the beer is prone to lacing in the first place), but it must be properly dried. A wet glass makes it nearly impossible for lacing to form and cling to the sides of the glass.
Certain malt varietals are said to promote lacing and head retention, but not all of them do this. Hops, however, can interact with the LTP1 protein and make more clingy, rigid foam.
Beers with higher alcohol content tend to have less head and lacing, but more legs (the streaks of liquid that slowly flow down the sides of the glass after swirling or drinking beer or wine).
Nitro beers also tend to have a very different textured and structured head and lacing than their traditional counterparts as nitrogen is largely insoluble in water, so it creates many small bubbles and a thicker mouthfeel.