Rinse Aid

You know, I am often asked why beer, despite being poured properly, doesn't maintain its head in the glass after pouring. Actually, I'm never asked that, but it's such a good question that I will answer it anyway. Rinse aid. The stuff that you put in the dishwasher that helps give a good finish on the dishes, glasses etc. What it does is it leaves a (harmless) film on the glass that serves to reduce the surface tension in any liquid placed inside. Unfortunately, the head on a beer relies on this surface tension to stop the bubbles collapsing. If you are not using rinse aid then maybe you are not cleaning all the detergent off the glass. Either way, rise the glass with clean water before using. Homebrewers may have this problem from their beer production process.

For real.