This is from an appreciation of scotch whisky blender Robert Hicks written by whiskey writer Charlie MacLean in WHISKY Magazine Issue 54, March 2006:
I asked him about how he maintained the consistency of Ballantine's and Teacher's from batch to batch.
"Do you save a reference sample from the previous batches?" I asked.
He looked at me pityingly.
"You have not been listening to what I told you about how whisky changes in the bottle. Even in the sealed bottle it changes slightly over time. We require unsold bottles to be returned for disgorging after five years (it used to be three years). Once the bottle is opened and air gets in, the change is much more rapid.
"So there is no way we can rely on samples from previous batches. We rely on our noses, on our memory of what the blends should smell like."