Cask choice and Maturation

1. Cask Choice

The Irish mature the majority of their whiskey in Ex-Bourbon barrels from the US. The American oak makes the whiskey smooth and a bit mellow.
Some of the special bottlings are stored in the more expensive Ex-Sherry or other wine casks. The wine casks are usually made of European oak. The flavours are more intense and sometimes bitter from the tannins but also more fruity from the residue of the wine in the porous oak.

Different sizes of casks
Different casks used at Midelton

During the maturation period some of the liquid evaporates. This is called the angel's share. As the whiskey matures the spirit becomes darker and smother.

Four casks with dropping level from left to right. Also from bright to dark
The stages of cask maturation at Midelton

2. The modern warehouse

In the historic days of the Irish whiskey production the spirit was matured in flat dunnage warehouses. The casks were rolled into the warehouses and stored in lying positions up to three layers high.
Today the demand is higher and the process is a bit more streamlined. The casks are put upright onto pallets and stored in higher warehouses. A new bunghole has to be drilled on the upper end of the barrel and enables to fill, probe, and empty the casks.

A big warehouse with pallets
A modern warehouse in Ireland

The tasting of the individual casks is very important and leads to the blending process. 

A big pipette, funnel remover and a tasting glass
Tasting tools

After the whiskey has matured long enough it is vatted in large steel tanks for bottling. Right before bottling the Irish whiskey is filtered. Most of the brands choose to chill the whiskey before filtering. This is done to prevent the whiskey from becoming cloudy when ice is added to the drinking glass. 

A filter with a lot of layers that are compressed
A whiskey filter

After filtering the whiskey is bottled and shipped internationally for you to enjoy your dram of Irish whiskey.