Well, I had probably the worst home-made espresso of my life last night, it was sour as hell, and smelled awfull .
I used some Sweet Marias decaf Donkey espresso blend (roasted 3 days before) with about 20% of HB Harrar added to add some aromatics. I don't know whether it was the Harrar or the Donkey blend (first time I have tried it), or the fact that the shot was a gusher at 15 seconds, but this was truly nasty. When I dumped the puck, this smelled bad too, way worse than the rubbery smell you get from roasting bad robusta .
The roasted Donkey blend smells really nice in the bag. I wonder if decaf goes like this when the shot is too fastt? I've had fast shots before, which weren't great, but were not this bad. I'll try the Donkey on it's own tonight and dial in for a proper timed shot and see. At least I can test lots of shots without fear of over caffeination .