I have read a bit about the steps in making whisky, but have not seen any description of how it is bottled. If you read various sources of tasting opinions and information, there are some significant differences in opinion from supposedly the same whisky. Most of the rating is probably due to personal bias, unless the tastings were totally blind which does not seem to be the predominant method used by whisky clubs and groups. Here's why I'm interested:
I am a chemist by education, training and experience and I make my living with chemistry as a small part of it. I know that water and ethanol are essentially infinitely miscible. But I also know that various organic components of whisky, such as esters, have differing densities. If you pour liquids of different densities together, and allow them to settle for a long period of time, the heavier liquid will migrate down to the bottom of the container due to simple gravity. There are other factors as well, such as molecular structure, polar and non-polar attractions, etc.
Depending on how a barrel is stored, how long it is stored, how it is handled after storage enroute to tapping the keg, the use of a "thief" during tasting in the ageing process when the blender makes decisions about finishing, and a myriad of other variables, how can we be sure that the sample we get from the first bottle is chemically the same as the sample from the last bottle from the barrel? Are barrels tapped like beer kegs in the end? Is whisky mixed in any way prior to removal to the bottling process, or is the first bottle from the bottom of the barrel and the last bottle from the top? We know that different batches (barrels) can yield slightly different bottles due to differences in the barrel wood and its history, but what is done to prevent variations from within a single barrel? It would seem to make a difference.