A lot of clever heads on this forum so I'm hoping you can clear something out for me:

I've noticed that Isomac has changed the boiler in some of their machines from copper to steel. And 1st-line is claiming that this is "better" than the copper boiler in similar models from competing brands:

http://www.1st-line.com/machines/home_m ... lenium.htm

What is the benefit of a steel boiler - i.e. why is it "better"? Copper has higher density than steel but steel has higher heat capacity. Copper, on the other hand, is a better heat conductor...

So is there some validity in 1st-line's claim?

Cheers,
C

Specifically 1st-line claims:

1st-line wrote:All stainless steel boiler - very heavy duty and thick! This is a much improved version of the copper boilers previously used and even better than what we see than most copper boilers, such as Quickmill.

Stainless steel is non-reactive vs. copper, though it's irrelevant for an HX espresso machine since the brew water is flash heated, not drawn from the boiler. The value of stainless steel for a dedicated brew boiler is more compelling since the water you drink has prolonged contact with the boiler. Even so, the typical consumer double boiler (e.g., Expobar Brewtus) or dedicated brew boiler (e.g., Quickmill Alexia) are small so their contents are flushed frequently enough that I consider claims of "stale" water dubious (see threads 1, 2, 3 and more revealingly 4 for copious discussions of this topic).

That said...

clausbmortensen wrote:So is there some validity in 1st-line's claim?

I agree that a stainless steel boiler is "better" than a copper one since it's non-reactive and stronger.

I've read somewhere that they are easier to descale since they are more flexible. Smack it with a hammer and the steel will flex so the scale will fall off. Copper would just dent.

1st Line IMO is a reputable company and carries a wide variety of brands and types of machines and I would think the statement:

All stainless steel boiler - very heavy duty and thick! This is a much improved version of the copper boilers previously used and even better than what we see than most copper boilers, such as Quickmill.

...is presented as nothing more than an honest opinion on an advantage of the particular machine.

Heckie wrote:...the statement [...] is presented as nothing more than an honest opinion on an advantage of the particular machine.

While I agree with you (and 1st-line), there is no qualification what makes it "better." If they believe it's better than the alternative copper boiler, they should state why. Otherwise such statements, in my opinion, sound like marketing hype.

Just a thought...

Considering the extensive (some might say expansive or excessive) amount of high quality stainless steel in the prosumer/commercial espresso machines, if stainless was indeed better than copper (or brass), why do copper boilers occupy such an overwhelming part of the market?

I realize copper may be easier to work with and has better heat conductivity. Tradition of the Italian shops (conservatism one might say) could also explain this choice.

--
Louis

Heat conduction is a negative as the boiler loses heat more rapidly.
+1 for stainless.

Stainless is more difficult to cut, form and weld without more specialized tools.
+1 for copper.

Should I care, OWOTO?
No.

+1 of course for 1st-Line.

As long as it's suitably thick (heavy-gauge) or wrapped in insulation, stainless steel is safely considered to be better. Stainless always retains heat better than copper. In fact, as temperatures rise, copper conducts heat at a faster rate than it does at lower temperatures.

Additionally, not only is stainless steel easier to descale, it actually resists the build-up of scale. Ever use a dishwasher with hard water? Scale builds up quickly on the plastic tubs but at a much slower pace with stainless. This benefit stems from its non-reactive relationsip with water. Yes, plastic and copper behave differently, but I believe the comparison is still valid.

Copper is a far easier material to work successfully with given the expected level of skill in the workforce.

Properly trimming, forming, and (especially) bonding/welding stainless steel requires a fairly high level of skill, a level not likely to be found at an acceptable price in the typical quasi-mass espresso machine production line.

Copper, on the other hand, is easy to form and trim using hand tools and simple machines. And acceptably brazing (bonding) copper requires no level of skill beyond that of basic plumbing.

While it is true that there's a lot of stainless in the average espresso machine, its use is limited to trim panels which are quite amenable to simple mass-production methods of stamping and forming. Nothing like assembling a boiler assembly.

One of the reason why the Isomac boiler was replaced with a THICKER and stainless steel one
is that THIS particular copper one develops pin holes on the welding
easier then some thicker boiler even in copper.