Use of cast iron teapot/kettle

.m.
Posts: 877
Joined: Wed Oct 11, 2017 3:26 pm
Location: Prague

Thu Sep 16, 2021 3:54 pm

DailyTX wrote:
Thu Sep 16, 2021 2:59 pm
.m. wrote:
Thu Sep 16, 2021 1:46 pm
DailyTX wrote:
Wed Sep 15, 2021 4:04 pm
This maybe off subject regarding tetsubin. Anyone has seen or encountered a Japanese tetsubin with copper inner wall and iron outer wall? I was curious if those design was to boil tea or for the purpose of better heat transfer.
Do you have any pictures or references to that?
It sounds impractical: the iron has lower thermal conductivity the copper and slows down heating, while copper is said not to have the best effect on water for tea (which is why i never tried so it's just a hearsay). And the fusing of the two layers sound kind of tricky, unless the tetsubin was electroplated with copper?
Here are a few photos I took. It's been a while since I tried to look up this kettle. Actually only the handle and the base have content of iron. Most of the kettle maybe made from copper. The metal was magnetic. If you zoom into the base, the inner ring can see red copper. The two side spots outside of the inner ring have rust.
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Beautiful piece. Looks old. Is it yours? From the photos it looks like it is all made of one metal alloy, at least i cant see any seams, maybe some kind of bronze or iron-copper alloy? According to wikipedia: " Bronze is usually nonmagnetic, but certain alloys containing iron or nickel may have magnetic properties."
DailyTX
Posts: 882
Joined: Wed Jul 03, 2019 4:43 pm
Location: United States

Thu Sep 16, 2021 4:20 pm

.m. wrote:
Thu Sep 16, 2021 3:54 pm
DailyTX wrote:
Thu Sep 16, 2021 2:59 pm
.m. wrote:
Thu Sep 16, 2021 1:46 pm

Do you have any pictures or references to that?
It sounds impractical: the iron has lower thermal conductivity the copper and slows down heating, while copper is said not to have the best effect on water for tea (which is why i never tried so it's just a hearsay). And the fusing of the two layers sound kind of tricky, unless the tetsubin was electroplated with copper?
Here are a few photos I took. It's been a while since I tried to look up this kettle. Actually only the handle and the base have content of iron. Most of the kettle maybe made from copper. The metal was magnetic. If you zoom into the base, the inner ring can see red copper. The two side spots outside of the inner ring have rust.
Image
Image
Image
Beautiful piece. Looks old. Is it yours? From the photos it looks like it is all made of one metal alloy, at least i cant see any seams, maybe some kind of bronze or iron-copper alloy? According to wikipedia: " Bronze is usually nonmagnetic, but certain alloys containing iron or nickel may have magnetic properties."
Thanks .m.
You give me an idea to look into bronze. It never came across my mind that the material could be bronze because I was so focus on the red copper showing on the bottom. It is a beautiful piece that I have been admiring it from time to time.
Andrew S
Posts: 704
Joined: Sat Jan 30, 2021 8:53 pm
Location: Sydney, Australia

Thu Sep 16, 2021 5:02 pm

Thank you @.m.: perhaps I'll try drinking some green tea boiled in a tetsubin next time I need to clean one, and see how bad it tastes.

And @DailyTX: I may be mistaken, but yours just looks like rusted iron to me, and not copper or bronze. Perhaps it was caused by leaving the lid on while there was still moisture inside, since the outside looks dark. It might clean up a bit and go back to a darker colour if you boiled some cheap green tea in it.

Andrew
DailyTX
Posts: 882
Joined: Wed Jul 03, 2019 4:43 pm
Location: United States

Thu Sep 16, 2021 6:02 pm

@Andrew S
The metal is pretty sure not iron due to lack of magnetic responses. If you use a tetsubin to boil green tea, the broth will turn black. This kettle boiled green tea, and the color looked like typical green tea. I can try to use acid or vinegar to clean the inside but taking the white stuff which I believe is calcium off, it may expose the metal to further oxidation. Like .m. Said, it’s beautiful as it is, I don’t want to damage what’s already beautiful to satisfy a curiosity ;)
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