I visited a local coffee shop supplier and bought a small frothing jug. They had one of the national barista champions visiting and I got a private hands-on lecture in stretching and whirlpooling. Would you believe - I have been keeping my wand too low all the time!!!! It seems that the wand has to be ON the surface of the milk, not "just under".
Rushed home, and stretching with the wand on the surface of the milk, I got the entire jug full of nice microfoam for the very first time. Previously I had always ended up with some milk at the bottom. I tried whirlpooling with the wand deep and alternatively with the wand on the surface, and that made no real difference - I still had the entire jug full of microfoam!!
And it still gets better. I had paid no attention to latte art yet, since I never had a jugful of microfoam to pour. Today, when I realised I had a full jug of the thing, I carelessly poured it into a cappa cup, and by mistake got an apple!!!! This really is the lucky monkey method working...
