Is it better/recommended to dose your coffee into a warmed basket and portafilter, or should they be cool, or does it not matter?

I do a quick flush of my machine in the morning, cleaning the shower screen, into a metal jug and without the portafilter attached, so the basket and portafilter are cold/cool when I dose the ground in and tamper.

I previously did it this way with my Micra Casa Lever as it helped to cool the group head which would get too hot after one pull. With my new LM Micra, is there any recommended practice or is it something to not worry about (not that I worry about much)?

I leave my cleaned portafilter & basket in the machine, ready for using the next day. So, for me, everything is hot. Between shots, I rinse quickly, give the Pf/basket a quick shot of hot water and dry the basket, before grinding in the next dose. So, my Pf and basket are always more or less the same temperature (hot) and dry for each shot. I'd hazard a guess that the vast majority of us do something similar.

"Be consistent"

For me, that has settled into basket is always cold and dry and prepped outside of the PF head. I keep the PF head in the machine so that it is warm. Keeping it uniformly warm seems easier to me than trying to get it down to my chilly kitchen temperature of 16-18 °C.

LondonBunny wrote:I previously did it this way with my Micra Casa Lever as it helped to cool the group head which would get too hot after one pull. With my new LM Micra, is there any recommended practice or is it something to not worry about (not that I worry about much)?

Jeff's advice of "Be consistent" is first and foremost.

That being said, if you want to be precise, then La Marzocco designed the Micra's brew temperature control algorithm to heat the group and heat the water in the group with the portafilter - the Micra's specific portafilter - in the group. You don't have to lock the portafilter in hard - just enough to take up the slack and a little bit further.

Arguably this only matters for the first coffee after cold start-up; however, the Micra's manual is very specific:

NOTE: It is important to leave the portafilter locked in the espresso machine when not in use. The portafilter must remain heated for the brewing process to function correctly.

For my Robot it's a cold basket and portafilter. For my FE-AR La Peppina, my Gaggia Factory, and my Faema Faemina I'll prep the basket outside the portafilter (cold). The La Peppina group is temp stable so I don't worry about the temperature of the portafilter but for the Factory or Faemina I'll dip my portafilter sans basket in a cool water bath for subsequent shots to help cool the group.

John Buckman of Decent Espresso brought up this topic with me about a year or so ago. Seeing how the DE machine can provide very precise measurements of things like temperature in the grouphead space, they dug deep into this question as a team and found that there was no noticeable change in shot outcomes/taste if the basket or pf were hot or cold. So it's possible that it's just another espresso myth that has been busted.

Basket maybe not so much but an E61 type portafilter is typically dense brass. My habit is to lock portafilter with basket into grouphead to let everything come to the same temperature. Guess you could lock in the portafilter only but it's easier to lock both in together. Whether a cold portafilter/basket makes a difference in the grouphead temperature before and during extraction I don't know, never measured it. For what it's worth I don't thermometer track my HX rebound flush either, I go by a set flush then time the rebound based on Scace data from others and listening to what the machine is doing.