The provocatively named "naked portafilter" is also appropriately named, because it reveals so much about your espresso shot . To those who are unfamiliar with this device, it is essentially a standard portafilter that has had its bottom cut away to reveal the portafilter basket. As a result, the espresso extraction is not routed through or concealed by a pour spout. Instead, the pour can be viewed in all its dynamics and richness, as it develops, presses through and pulls away from the basket's micro-screen.Recently, Jason Prefontaine and myself have been brewing & watching shots using a naked portafilter we jerry-rigged from a standard issue piece. I think Jason may have made ours using a hacksaw or other tool, although you can buy these pre-cut and nicely finished, at least for LM machines. Anyway, this rough little device is a total arbiter of truth. It reveals for example how evenly we have tamped. If the tamp is uneven, even fractionally, you can see it. The coffee pour will tend to start and concentrate on one side of the basket, before spreading out. Brewing with a naked portafilter also reveals other truths like how hard the tamp was, when the extraction is TRULY complete, and if you are over-extracting from any point inside the basket.
Typically, the quality of ones espresso pour is determined by the look and taste of the extraction in the shot glass. The naked portafilter takes this one giant step forward, allowing an almost complete, albeit qualitative analysis, of your coffee preparation and extraction in situ. It allows the barista or aficionado to watch a live 25 second play-by-play as the extraction develops, coalesces, and falls into the shot glass in all it's tiger-striped glory (hopefully). The naked portafilter is a potentially valuable tool in fine-tuning your skills around a particular coffee's foibles and idiosyncrasies. Knowledge like this is power.Also of note, we have been able to "see" huge differences in shot character resulting from the adjustments we make to pre-infusion. The exact quality, pressure, and volume of our pre-infusion setting changes our extraction results significantly in very particular ways, taking us far beyond the realm of simple progressive pre-infusion. I wonder if anyone else who has used a naked portafilter has any insights on the expanded effects of pre-infusion or has experienced this as well? I found one interesting link that discusses some of this stuff, which I found to be an enlightening primer in terms putting our own experience into context. Check this out!http://www.home-barista.com/naked-extraction.html