In the course of 24 hours recently I had a really great long black and a really-not-so-good long black.
I have rarely knocked back a coffee, but I didn't drink the really-not-so-good one: it was scalding hot, brimming over the top of the mug and devoid of crema (and flavour).
It's possible that no brew is so misunderstood as the long black. The crimes against long black drinkers include:
1. Pushing the button on an espresso machine and letting it extract until the cup looks full enough. Not many baristas do this any more, but they did, once upon a time. The resulting cup will be horribly over-extracted and burnt-tasting, not because it is burnt, but because one of the compounds that is extracted from coffee once you pass 30 seconds of extraction tastes of smoke.
2. Pulling a double shot and then filling the cup with really hot water from the tap on the espresso machine (or worse, the steam wand). Doing this breaks up the crema and disperses the aromatic compounds trapped in it, so the flavour palette is limited to what you can taste in your mouth - sour, sweet, salty, bitter, umami - without the enhancement of what you can smell: a much greater range (a recent Rockefeller University study put the number of aromas that the human sense of smell can detect at 1 trillion).
3. Using water from the machine can also leave the long black drinker with a cup of coffee that is too hot. This is what James Kilby from Padre's Brunswick East Project calls the social angle: "Water from the machine can be close to 100C," Kilby says. "So the long black drinker is still waiting for their coffee to cool when everyone else is finished."
The way to make a good long black is to pour the (not too hot) water first, then add the double shot on top. Some cafes pour from a hot water tap on the espresso machine, and the cup can take some of the heat out of the water. At Padre they pour 100 millilitres of water at 70 degrees from an urn.
It's easy to tell if a long black has been made properly - it will arrive with some crema (not as dense as a short black because of the bigger surface area), and it will be ready to drink, temperature wise.
The long black is a great way to enjoy lighter specialty espresso roasts: the extra water lets the flavours open up a bit. You get the fuller mouthfeel of an espresso - and the chance to linger over your brew.