A few years ago I attended a rum blending seminar with the master blender from Appleton. We used four different blending rums. Today I attended a webcast with the master blender of Johnny Walker, Andrew Ford, to celebrate the 100th anniversary of Black Label. They gave us seven blending whiskeys and all of the other necessary apparatus: a nosing glass, a measuring beaker, and a funnel. The blending whiskeys were all 12 years old and 40% ABV.
They were: grain, lowland malt, Speyside malt, sherry cask malt, highland malt, island malt, islay malt.
One thing I learned is that blenders normally work with the whiskey at 20% ABV.
As blended scotches go, Johnny Black is probably my favorite, so I found it interesting to break it down into its component parts. Andrew said grain whiskey is normally about 50% of the blend (for all blends, not just JWBL). I got a blend I liked using 40ml grain, 10ml each of lowland, speyside and highland malt, 15ml sherry cask, 5ml Island and 5ml Islay. With the Islay especially, a little goes a long way.
The grain whiskey is aged in first refill bourbon casks and has a lot of bourbon character. By contrast, the Islay is aged in 2nd or 3rd refill casks, so it is very light and has very little barrel character. It's there for the smoke. A surprise was how important the sherry cask malt is to the blend. I started with just 5ml and when I went to 15ml it made a big difference. Andrew said it's not the sherry you're tasting, but the European Oak, which gives a very different flavor than the American Oak.