On January 22 at the Cast Iron Chef event at Fort Mifflin, I will debut the Regimental Brewmeister’s new 1 barrel brewery set up including a 30-gallon kieve (aka keeve) and a 30 gallon kühlschipp.(AKA koelschip). As we strive for ever increasing levels of authenticity to both the beer and our experience brewing, this new equipment takes us back to the basics of 18th Century zythology.
Modern breweries make good use of literally centuries of scientific study in heat transfer and exchange. In our modern breweries, we have highly efficient means of heating and cooling our wort but in in the 18th Century, all of this was much more primitive. Those of you who have cooked over an open hearth or attended one of my brewing demonstrations understand the complexities of heating wort over a wood fire. Its constant work because the fire is either too hot and the kettle boils over (generally extinguishing the fire!) of its not hot enough and it takes forever to bring the kettle to a boil. Of course, what goes up must eventually come down so as if that weren’t enough aggravation to heat the wort, once you have boiled it, you must be cool it down enough so that it doesn’t kill the yeast when you try to start the fermentation.
When making small batches of beer, the wort generally cools quickly enough on its own through simple radiative heat loss. The ratio of surface area to mass on a 5 – 10-gallon copper kettle is such that within an hour or two enough heat is lost to take the wort temperature from boiling (100-110C) down to “blood temperature” (35-39C) so that yeast can be inoculated into the wort and start the fermentation. The problem is that if we allow that cooling process to extend much beyond 2 hours, bacteria will begin to grow souring and even spoiling the beer. As we scale up the brew batches, we encounter a problem getting the beer to cool fast enough to not spoil.
Colonial brewers needed to produce BARRELS (135-140 litres) of beer each day to keep up with the demand. Brewing is a time-consuming task so multiple small batches is not really an option, they needed to brew on the 1–5-barrel batch scale (we are keeping to 1 BBL for transportation reasons). When you get to this scale, simply waiting for the beer to cool radiatively in not going to work (mu computations indicate this would take 7-10 hours) as the beer would likely spoil before fermentation could even begin.
Now in a modern brewery, this is not an issue. We have heat exchangers that literally pump out the heat. These rely on a constant flow of chilled water which ultimately requires some sort of chilling apparatus (like a heat pump) that runs on electrical power. Clearly such modern approaches were not employed in the 18th Century so how did they cool the beer?
One approach is to employ a kühlschipp. A kühlschipp is a very wide and shallow basin with an open top so that the wort remains exposed to the air above it. At the end of the boil the boiling wort is transferred directly to the kühlschipp and it is allowed to cool through outgassing, evaporation, and occasionally by counterflow chilling that happens when a nearby stream is redirected to flow under the kühlschipp (but not in contact with the wort). Kühlschipps are traditionally made of wood but toward the end of the 17th Century, copper, tin plated iron, and other metals became more common. The high surface area-to-volume ratios has three functions: cooling, aeration of the wort, and separation of the cold trub. In some situations, a hop-filtering basket (Hop Jack) is attached to clarify the wort before fermentation.
Because the hot wort is left in the kühlschipp for an extended period of time, often overnight, as it slowly cools the organisms in the air, bacterial and yeast imbedded in the wood, and yeast deliberated inoculated by the brewer all end up in the fermentation. The result can be very complex and rich assortment of interesting and challenging flavors like a Belgian lambic or they can have funky sour tastes. When done right, Kühlschipps create beer’s equivalent of “terroir” which is the vintner’s term for the confluence of everything local — soil, precipitation, climate, etc. – that determines the unique characteristics of a particular region’s wine.
In our post Prohibition world, almost all beer is brewed using much the same equipment, material and methods. We make a lot of noise about very small differences in craft beers but in the wider range of beers and brewing, there is so much more. The kühlschipp gives us some insight into what beers and brewing were like and could have evolved into. In the experimental world of “living history”, we are relearning the art and science of heating and cool wort.