Stainless steel vs. copper boilers - Page 2

#11: Post by **JohnB.** » April 19th, 2013, 8:51 am

another_jim wrote:It would need to be long and finned if it were, since it doesn't conduct heat nearly as well as copper. I wouldn't want the job of designing a stainless HX inside an espresso machine

For the first several years of production the series 2 Speedsters used a plated copper Cimbali HX. There were some issues with corrosion so Kees switched to a custom built stainless HX which I now have in my machine. Like most of the parts that Kees produces it was a work of metal art that I could have displayed on a shelf next to my cups & tampers.

#12: Post by **another_jim** » April 19th, 2013, 9:05 am

Yeah, Kees would enjoy a challenge like that. What did he do to increase the surface area?

#13: Post by **etout00** » April 19th, 2013, 9:12 am

bobmccarthy wrote:Jim,

I think the Cimbali Jr boiler is in stainless. Wouldn't the HX tube also be in stainless?

bob

I briefly owned a La Cimbali M32 Bistro (same boiler/HX configuration as the Junior DT1) and remember that the HX tube was in fact copper, while the boiler itself was stainless.

#14: Post by **JohnB.** » April 19th, 2013, 9:38 am

another_jim wrote:Yeah, Kees would enjoy a challenge like that. What did he do to increase the surface area?

Nothing exotic but but keep in mind these are about 6" long & 1.5" in diameter. The stainless version looked to have a higher volume but I couldn't swear to it. Considering that the brew group assy. & both boilers are stainless & that the Speedster is one of the most temp stable machines on the planet maybe stainless isn't such a poor choice for these applications after all. The massive steam boiler in the Spirit Triple at the Boston show was copper with the stainless brew groups/boilers coming directly from the Speedster.

#15: Post by **bobmccarthy** » April 19th, 2013, 9:48 am

etout00 wrote:I briefly owned a La Cimbali M32 Bistro (same boiler/HX configuration as the Junior DT1) and remember that the HX tube was in fact copper, while the boiler itself was stainless.

I would have thought galvanic corrosion would be an issue.

bob

#16: Post by **Carneiro** » April 19th, 2013, 9:55 am

The HX on Speedster has to pre-heat water for the big group boiler, so it's not so critical... A small HX for a thermosyphon should have more heat transfer capacity. I wonder how does the ECM perform, it seems the boiler and HX are SS, and it's the tradicional 2-2.3L boiler with small HX (120-200ml?).

#17: Post by **spressomon** » April 19th, 2013, 12:58 pm

Related: When drinking wine, coffee, bourbon, etc., from a SS cup there seems to be a flavor component from the SS I don't like. Whereas drinking the same beverages from a titanium cup doesn't impart similar off-putting flavor. Non scientific...yes.

I'd venture to guess copper as well as SS boilers impart some flavors of their own, small or large, to the cup.

Maybe titanium boilers will be next

#18: Post by **another_jim** » April 19th, 2013, 1:36 pm

Steel is traditionally held to be bad for acidic components; salads, for instance, were never made in steel bowls. But I think this may be unfounded; after all, the wine you think gets a taste cast from the steel cup was fermented in a steel vat, and maybe aged in a steel barrel.

April 19th, 2013, 3:11 pm

Carneiro wrote:I don't think Joe is wondering about thermal differences from SS, copper and brass. If I understand he's asking about taste.

Some times I drink espressos from La Marzocco GS/3 or Strada at the importer show room. Just another day I went to the company that has a Kees Spirit waiting for the Brazilian certification, and I confess that those machines, all SS boilers and groups in general excels others I used.

But, the group and dispersion screen of each machine are different... I wonder if a E61 machine with tradicional copper boiler/HX will differ from a SS boiler/HX (new ECM for instance). The only copper part would be the pipes (but it could be SS) and the group is brass...

These days I'm using the Faema Velox I restored, and the little boiler is brass, big heat element is copper. The water always come out with a distinct smell, and if I flush 2-3 times the boiler size, it gets better, but I don't know how much it would improve with something more inert. Just for comparison, the Gaggia Tell I'm using too has now a electroless nickel plated boiler, so only brass inside the group. There is no smell like the Faema or other copper boiler machines I remember. At the same time, the Elektra Semiauto has almost no smell, but the HX is very small and I flush it a lot during a session.

Márcio.

Are there people who have repeatedly sampled espresso or water from multiple machines, stainless boilers and groups (thank you Marcio!) vs copper and brass components vs nickel-plated components, and have not noticed a difference in odor or flavor?

#20: Post by **another_jim** » April 19th, 2013, 3:52 pm

Yes, lots of people have repeatedly and scientifically blind compared the same machine made in copper and steel

. What are you trying to say here other that you are very impressed by steel? Absolutely everyone I know who has ever done blind shot comparisons will be rolling their eyes at these speculations and assertions. Nobody can taste what you are claiming to taste.