my pick for technika profi series is the boiler is made of stainless steel. Thought this would be better material just like the one in marzocco gs3
Large Ss boiler is also used in synesso, olympia, kvdw , a quite a few other high end brands. Small Ss boilers is also used in some lower end machines like breville I think. Rockets uses nickel plated brass I think to prevent the brass from leeching lead.
A good ss boiler is expensive to make compared to brass and copper. Ss is harder metal to work with. There was some discussion on ss imparting a flavour to the water but very much doubt it matters much.
Whether the brass leeches lead depends on the alloy used.
I worked for a company dealing with pans and pots in Korea.
Pure S/S is actually cheaper than copper and the thermal conductivity is pretty bad, so i believe it's clad with copper. In short terms, copper core or layered copper in between.
If it's heating by just pure S/S, then expect very uneven heating and a much longer heat up time.
Since the job for the boiler is to heat up and keep warm, actually pure copper is better.
In cookware, we prefer stainless steel, because it's tougher , affordable, neat and non reactive. We can control the handle to be not hot though it's S/S because it conducts bad. So overall looks alright as a single piece.
If the boiler is sitting inside the coffee machine, not anyone going to dent and damage it, copper imo is a better material to heat up faster and to keep warm longer. This saves power and quickens at least.
S/S maybe non reactive but copper is not a nasty metal, and it's essential for health, so no clear advantage on that.
Another possible reason, maybe it's to insulate it, which is very unlikely because the S/S will still conduct heat.
I will skip brass totally no matter what grade it is.
I get gassy and all that nasty stuff. Once in a while I'll succumb and drink a small latte. The rest of my latte practice products goes to my long suffering partner haha.
