Ask Mr. Wizard

Counter-Pressure Bottling Tips



Can you give me tips on using a counter-pressure bottle filler without the bottles over-foaming?


If there are problems, what I would check first is the length of the fill tube. One of the most important rules of bottle filling is to gently fill the bottle. There are two types of filler-tube designs used in commercial breweries: long-tube and short-tube fillers.

Short-tube fillers fill the beer by directing its flow to the inside walls of the bottle, and the beer cascades down the sides of the bottle during filling. Long-tube fillers extend all the way to the bottom of the bottle and allow the beer to fill from the bottom up without excessive turbulence. If the tube ends farther from the bottom, the beer will start to foam as it falls from the bottom of the fill tube to the bottom of the bottle. If your fill tube is too short, extend it.

The next rule of bottling is that beer foam breeds more beer foam. This is because gas is released from beer when nucleation sites are present. Nucleation sites include rough spots on a beer contact surface, such as an etched glass, crystals in beer (for example when salt is added to beer), and beer foam. Toward the end of filling the bottle, leave some space at the top and do not allow any beer to squirt out of the gas vent valve. If the bottle is filled all the way up, beer will squirt out of the vent tube during the depressurizing step and foam will form. If you allow beer to squirt out of the vent tube during filling, foam will form. In both cases more foam will form when you remove the fill tube. This rule applies not only to filling beer bottles at home but is also used in commercial bottle machines. In fact the fill tubes on a commercial filler are designed so that beer cannot be filled all the way to the top of the bottle.

On the same line of reasoning, the beer bottle itself is often the culprit of foaming, especially when returnable bottles are used for bottling. Glass is not always a smooth surface and imperfections in glass make beer foam. When beer bottles are cleaned and re-used at the brewery, the surface of the bottle becomes etched and this problem is exacerbated. Filling a wet bottle is easier than filling a dry bottle because a film of water on a bottle’s surface is smoother than a dry surface and, you guessed it, results in less foaming. Commercial filling lines have a bottle rinser preceding the filler to ensure that beer is filled into wet glass.

These rules are the basics of bottling and when used on most beers things usually go pretty well. If I sound a little unsure, it’s because bottling usually provokes brewers to swear a bit more than do other operations. Bottling beer is never a sure thing. Two variables that often throw a kink into the mix are beer carbonation level and beer temperature. I prefer to choose a pressure and temperature combination that results in the carbonation level I am after and allow the beer to carbonate over several days. This method is more predictable and reproducible than high-pressure carbonation followed by a reduction in keg pressure.

Response by Ashton Lewis.