The first distillation takes place in the wash still, into which the wash is added and heat is applied. As alcohol boils at 78.1oC, its vapours are the first to rise from the wash and depart upwards through the neck of the still. Copper piping leads from the neck of the still to a horizontal condenser where the vapours are converted back into a liquid; this is the first of the spirit and it has an alcohol volume of approximately 40%. The spirit captured from the wash still (now known as low wines), is now fed into the second or feints still. Here the spirit captured has an alcohol volume of approximately 70%. Finally, and almost unique to Ireland, the feints are fed into the third or spirits still. The spirit is filled into oak casks for maturation and now has an alcohol strength of 85% vol.
Throughout the entire distillation, the master distiller at Midleton Distillery, Brian Nation, will carefully control every step of the process. The first alcohols and flavour compounds to come from the stills are very high in esters which contribute to the fragrant, floral and spicy characteristics of a spirit. However the first runnings, known as ‘heads’ or ‘fore-shots’, are too high in concentration to be enjoyed and also contain fusel oils and esters left behind from the previous distillation. The distiller monitors the heads, deciding when he can make a cut and start collecting the 'heart’ or ‘middle cut’ of each distillation. Similarly with the ‘tails’ there comes a point when the balance tips towards undesirable flavours again. The distiller will monitor the hearts to decide when to redirect the tails. Heads and tails are reused in subsequent distillations to ensure that nothing goes to waste.
Copper plays a vital role in pot still distillation apart from its excellent heat conduction. The production of esters in distillation can include highly volatile and pungent sulphur compounds that are undesirable. The copper has a chemical reaction with sulphur to form copper sulfate which remains behind in the still. The longer the contact time between the spirit and the copper, the lighter the spirit will be in style.
Hand made, copper pot stills are crucial to the distillation process. Pot stills can can vary in style and shape - onion-shaped, conical, ball and lantern - resulting in different styles of distillate as the shape and style of the still will vary where the distillate condenses. As the vapours rise up the neck of the pot still and the temperatures gradually decrease, the less volatile components will condense and fall back into the pot, this is referred to as reflux. These tend to be the heavier congeners resulting in a lighter style and higher strength spirit as the lighter components are better able to escape into the neck. The head of the still is attached to the pot and again varies in size and shape - tapered, straight-sided, short or long. The lyne arm connects to the head via the swan neck and this leads to the shell and tube condenser where the vapour is converted back into liquid form. In Midleton we have the largest pot stills in the world in operation with three full sets of three copper pot stills as of 2017. Our garden Stillhouse now holds two full sets allowing our Master Distiller to create different styles and types of distillate depending on what brand he is distilling for.