I’ve always been curious to see how a shot pulls from a lever machine using a naked portafilter – so, we rebuilt an old Simonelli ISX lever and drilled out the portafilter. Here’s the vid:
What we noticed is that there is an odd & disturbing cone of foam that forms at the end of the shot (we were using a double PF basket and at the point of shooting the video, hadn’t bothered setting the grind for the lever machine – so, it was a little fine). When I first saw this – I thought there was something clearly wrong. I have just descaled the machine I figured there was still acid or something in the boiler. We later came to the conclusion that there must be air at the top of the column of water in the cylinder that is forced through the coffee after the water and the air must be forcing the abundance of oils/fats through the grounds after the first pull.
Anyway – I find the old lever machines interesting & have been studying the pressure profile of these machines. At some point I’ll post what we’ve learned and try to explain why lever machines deliver a soft & creamy tasting espresso.