A note on the plastic steam tube:

The Micra has a world class double-walled no-burn steam wand that stays cool to the touch and has the same powerful steam flow you'd expect from a La Marzocco. With no PTFE tube inside limiting the steam flow, LM has achieved comfort without compromise. However, upon removing the group cover, it is hard to miss that the tube running from the steam boiler to the steam valve is not copper like it is on the hot water side. Instead it is clear plastic.

I was commenting to a friend on how nice the steam is on the Micra, and that I appreciate the smart use of what I assumed was a "Poly" tube between the steam boiler and the steam valve. The tubing provides a heat break between the boiler and the steam valve and is very effective at keeping steam condensation at the steam valve to a minimum. My observations with the group cover removed was that there was no more than a gram or two of liquid condensate in the clear tube and that when purging the wand, those couple of grams were all that needed to be purged. The steam has such great velocity through the double-walled wand that there doesn't seem to be any additional moisture generated as the steam valve comes up to temperature, which is a wonderful thing.

The response was "Poly? As in Polyethylene? That's concerning, as steam temperatures seen in the Micra are right at the upper temperature limit of Polyethylene." Well, fair question:

So I looked up the part info in the Micra parts list, and it is listed as PFA tube. Turns out PFA is a resin in the same family as other perhaps better known flouropolymers, such as FEP and the ever-present PTFE. PFA has "the best of both worlds" with respect to the other two, and is an excellent choice for this application. Two sources I found list the following as key attributes PFA tubing is known for:

https://holscot.com/what-is-pfa-tubing/ is a great resource for learning more and has this executive summary on the product:


Another resource I found was https://www.fluorotherm.com/products/fl ... fa-tubing/ which has the following list of key properties:

Great stuff, and nice to see LM choosing wisely when it comes to material choices, especially when it looks like it could be a simple cost saving measure. It is miles better than the conductive tube that runs to the low-mounted steam valve in my GS/3, which condenses what seems like several tablespoons of water in the tube every time I use it.