Why Copper?

By Chris Morris • Photos Provided 

In previous articles in the Voice, we have asked and hopefully answered many questions about the “Why’s” of the Whiskey industry in general and Kentucky Bourbon specifically. For example, “Why does Bourbon go into new charred oak barrels?” “Why does Bourbon use corn as its base grain?” “Why was Kentucky the birthplace of Bourbon?” These and other questions have been answered with a common theme or answer. “It was the time and place.” 

So previous answers have revolved around the use of wood, the use of water and the use of grain in the crafting of a Whiskey and again particularly a fine Kentucky Bourbon. Now we will address another aspect of the production process, distillation. We have established that every Whiskey is a Whiskey. Every Whiskey follows a global standard and therefore every Whiskey distillery has the same five sources of flavor or processes to use. Whether it uses all five sources as a defining aspect of its flavor profile is up to each and every individual distillery/brand. The five sources of flavor are water source, grain recipe, distillation, fermentation, and maturation methods or processes. 

Let us take a look at distillation, the equipment used for it in particular. Distillation is performed in one of two broad processes: it is either conducted in a continuous process or in a batch process. The continuous process requires the use of column stills, sometimes called coffey stills. The batch process utilizes pot stills. Today’s stills are manufactured, using either stainless steel, copper, or a combination of the two. Legend and lore readily proclaim copper as the preferred metal used in the construction of a still. Again, whether it is a column still or a pot still copper seems to be the preferred metal. Based on history and my experience, I can vouch for the fact that copper is the preferred metal to use in a still. Why? As usual the answer can be found in time and place. 

Distillation and the production of Whiskey have been taking place for hundreds if not thousands of years. The historic record will show that stainless steel was not available to our predecessors whether they were in Scotland, Ireland, or frontier Kentucky in the 1700s. 

History tells us that copper was one of the first metals that man was able to isolate and refine. It is one of the few “native metals”, meaning metals that occur naturally in a directly usable, unalloyed metallic form. The other metals that were available in their pure form are gold and silver. Both are more rare and less versatile in a manufacturing process than copper. So copper was more readily available or easily extracted from or and importantly very malleable. Early man could smelt it, pour it and shape it. 

This led to early use in several regions, from as early as c. 8000 BC. Thousands of years later, it was the first metal to be smelted from ores, c. 5000 BC; the first metal to be cast into a shape using a mold, c. 4000 BC; and the first metal to be purposely alloyed with another metal, tin, to create bronze, c. 3500 BC. 

So eventually man began to make pots, pans and other vessels out of copper simply because they could, and it was durable. They could shape it in ways that were difficult to do with ceramics. So eventually, when they began to make the first stills, Alembics, it made sense that copper was used. Other metal combinations such as copper and tin, which when combined make bronze, were probably also used. But over time as whiskey or other spirits made in various types of stills could be compared it became apparent that a still made from copper was the way to go. Why? For two reasons. 

First, copper is a great conductor of heat. It distributes heat evenly so there are no hot spots in a copper vessel. Other metals will have hot spots which can lead to the scorching of the liquid above that hot spot. So, if you are distilling, a fermented mash of grain and some of it is being scorched in the still that will result in a burnt grain note. That obviously is an undesirable flavor characteristic. That will not happen in a copper still. 

Copper, it turns out, also has another notable feature. It removes sulfur from whiskey. Where does sulfur come from? It comes from the grain recipe especially if you use malted barley. If you have too much sulfur in your whiskey, it will have an off note. The old time Kentucky distillers called that off note “skunk.” In Scotland it is called “cabbage.” I don’t know about you but neither of these sound appetizing to me. 

Today when you make a visit to the Woodford Reserve Distillery you will find that the still floor features six copper pot stills. A visit to the Old Forester Distillery on Whiskey Row in Louisville will reveal the three-story copper column still – “Big Penny.” Now you know why – they not only look impressive but play an important role in creating a clean flavor profile for both Woodford Reserve and Old Forester. Thank goodness our ancestors through trial and error gave us copper stills.