Suppose someone is doing a buffet or an event with an espresso machine that is single group like a Linea Mini. Since it is a single group, how do you handle the portafilter cooling off with back to back shots? I would imagine after you rinse it after a shot, it can't really sit that long in the grouphead before the next shot to fully heat up.

Either use a damp cloth or a brush rather than rinsing with cold water. Personally, I just remove the basket to fill...easy peasy.

This. ^^

linuxAndJavaScript wrote:Suppose someone is doing a buffet or an event with an espresso machine that is single group like a Linea Mini. Since it is a single group, how do you handle the portafilter cooling off with back to back shots? I would imagine after you rinse it after a shot, it can't really sit that long in the grouphead before the next shot to fully heat up.

You could use the hot water spigot to rinse (just a brief burst of hot water) and then wipe the PF dry. The steam boiler autofill may kick in briefly while you are prepping for your next shot, but with a large boiler like the LMLM has, that should not hold up your workflow significantly.

One solution for mass production, such as a coffee cart or a party at home, is to have a container of hot water, into which the portafilters are put after rinsing. One of those little induction heaters would be ideal, as you could set the temperature. Pull a PF out of the pot, dry the basket, and you're good to go. This would, obviously, not be practical for only a couple of back-to-back shots. As already mentioned, at home, where we just have a few shots in the morning, I sometimes just hit the PF with a bit of water from the hot water wand when I'm feeling, particularly fussy . Really, though, the mass of the PF is so huge compared to that of the basket, that I question whether doing anything is necessary. As long as the basket is rinsed out with a quick slosh of water, the retained heat from the PF is going to transmit to the basket. What's more, we put room temp coffee into the basket anyway.

That technique posted by HB would certainly work as regards maintaining portafilter temperature, but I'd worry that just wiping the grounds out that way would eventually lead to build up of coffee schmutz (I just coined the term) on the sides and in the holes of the portafilter that would adversely affect the taste of the espresso...though probably not so much for milk-based drinks.

That problem might be minimized by the use of a nanotech coated basket or bottom-of-the-puck filter paper. Or just knocking out the puck and rinsing the basket in very hot water...

Butane torch to reheat the basket and expel moisture at the same time after rinsing?

I'm probably wrong here, I don't think the temp of the portafilter matters as much as the temp of the basket.
Is it the hot portafilter that keeps the basket warm between shots?

For me, I just toss the old puck, turn the pump on for a few seconds to rinse, wipe with towel and on to the next shot (3 per morning).

Bottomless portafilter, knock, hot water rinse, wipe, and go.

Yeah, but unlike a bottomless PF, a spouted one presents a mass of metal (usually plated brass) that gets in contact with the coffee and if cool enough could cool down the coffee enough to adversely affect its taste, but that's a whole other subject for discussion.