Irish Whiskey distillation
1. Pot Still Distillation
The Early Start
The Irish whiskey industry was the first to produce whiskey in large quantities. Back in the days the only distillation method was the pot still distillation. In order to satisfy the high demand most of the distilleries built huge pot stills like the ones you see in the museum of the Old Midelton distillery. These pot stills were large pieces of sheet metal copper riveted together. They were mostly fired by coal. Cleaning them was a long and hard job.
There was a separate room below the pot stills used to fire the pot. The workers had a bell and a string to communicate with the stillman above in this very loud and busy environment.
The big stills of the distilleries needed cooling after the lyne arm. This could be either done by a steady flow of cold water or by providing a large enough heat sink in the form of a big tub.
The process starts by filling the wash into the first pot still called wash still. It is then heated and produces an alcohol solution called low wines with about 20 to 25 vol %.
By heating the wash to a certain temperature the lighter alcohol evaporates rise up in the neck of the pot still. The rest of the wash remains in the pot. The vapor is then cooled down and gathered in spirit receivers.
In order to get whiskey the process needs to be repeated. The first low wines is then filled into the second pot still. Usually a smaller one that produces alcohol with 60 to 70 vol %. At Bushmills and New Midleton the classic way of triple distillation is still performed. The new spirit (raw whiskey) still does not nearly taste as much as whiskey. However the form of the pot still determines the later taste. To make it whiskey the spirit needs to be aged in barrels for at least three years.
If you want to learn more about pot still distillation read this article.
2. Column Still Distillation
The first fall of Irish whiskey began with the invention of the column still distillation in Scotland. This process allowed a continuous and more efficient distillation of cheap whiskey.
Nowadays Irish whiskey, mainly grain and blended whiskey, is also produced on column stills. High quality Malt whiskey is still produced on pot stills only.
The column still uses fractional distillation to separate the spirit from the wash. The way it works is that the wash is inserted high and flows down through the still. At the bottom steam is inserted and rises against the stream of wash. The alcohol is more likely to evaporate and rise in the still. In the end the different elements in the wash are distributed through the whole still. The lighter alcohols are at the top and the water and residue are collected at the bottom. Most distilleries have more than one coloumn still to have a better separation.
A column still is made of many sections that are bolted together. Inside these sections you have even more layers that slow down the flow of the liquid downwards, but lets the steam rise through from below.