The following images are taken from an experiment by one of our suppliers, examining the effects of limescale, lipstick, excessive rinse aid, heat and dirty glass washers on the quality of beer in glasses. They all use lager poured into a 'head retainer' glass, which has nucleation points etched into the base of the glass to promote foam generation.
Good Clean Glass
With a clean glass, you can see a crisp, clean 1cm tall head at the top of the glass, which is retained for a decent time. The lager is fizzy to taste, and the gas release is controlled. 15 minutes later:
Not a lot has changed with a clean glass, the head has been retained, the lager is still fizzy, and the release of gas is continuing in a controlled way. 15 minutes more:
Half an hour after the initial pouring of the lager, there's still a head on the glass; the lager is still fizzy. The bubbles are still rising from the bottom of the glass in a controlled manner.
Clean Glass with Limescale deposits
While this glass is still nice and clean, there is some limescale in it, from a small build up in the glass washing machine used to clean it. Because of this, the head has grown excessively and breaks down unevenly over time. The gas is escaping very quickly, and the drink will be flat to taste very rapidly.
Clean Glass with excessive Rinse Aid residue
This glass was washed in a machine with the rinse aid dosing turned up to high, and therefore has come out of the machine coated in residue from the rinse aid. There is no head, and no glass release to speak of, and the lager is flat to the taste.
Limescaled Glass with Rinse Aid Residue
This glass is suffering from limescale deposits and has been washed with too much rinse aid. Because of this, there is not head on the pint, and the drink will be flat to the taste, but bubbles are being released from the bottom of the glass, they aren't controlled and will dissipate rapidly.
Clean glass with Lipstick residue
While this glass might appear clean, it still has some lipstick residue left on it from a previous drinker. The gas is escaping from the drink very quickly, and rapidly the beer will be flat to the taste. There's also an excessively large head at the top of the drink, which breaks down quickly and unevenly.
Limescaled glass with Lipstick residue
The above glass has been washed in a glasswasher with limescale build up which has been transferred to the glass. It has also still got the residue of a previous drinkers lipstick. While there is a 1 cm head at the top of the glass, which is retained decently, it breaks apart unevenly. The gas is being released quickly, and rapidly the drink will be flat to taste.
Glass not cooled from Glass Washer
This glass was poured straight into a warm glass, directly taken from a glasswasher. The head is excessively large and breaks apart quickly, but the gas is being released evenly.
Limescaled Glass that hasn't cooled
This glass has limescale deposits from the inside of the glasswasher that has just been removed from, and the lager has been poured into it without allowing the glass to cool down. The head is excessively large and breaks apart unevenly. The gas is being released from the drink uncontrolled.
Clean Glass washed in a dirty glass washer
This clean glass has just been washed in a machine that hasn't been cleaned. The head is more significant than it should be and breaks apart unevenly. The drink is flat to the taste, and despite being in a glass that promotes fizz, there is no gas release to be seen.
Limescaled glass washed in dirty glass washer
Much like the previous glass, this glass has been washed in a machine that hasn't been correctly cleaned between uses, but it also has limescaled deposits. The head is excessively large, and breaks up unevenly, and has no signs of gas being released in the drink
As you can see from the images above, Limescale leads to excessive fizzing, too much head and beer that will go flat prematurely. Rinse aid residue (from the dosage of the chemical being set too high in the machine), lipstick, heat and a dirty glasswasher can all have a defoaming effect, which will make the head go flat. Limescale absorbs lipstick, rinse aid and dirt and exacerbates the problem, which highlights the importance of installing and correctly operating a water softener.