Oct 13th 14 2:20 am
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Gunk in teapot?

by sainthurricane » Oct 13th 14 2:20 am

Hello! I joined this community in hopes of getting a question answered. I just bought a new Iwachu cast iron teapot here in Japan. It's lovely. However, if I brew the tea and leave it in the pot for longer than an hour, some black stuff appears inside the pot and turns the tea black. I think there is an enamel coating on the inside, so I'm not sure why this is happening. It does this with any tea I use.

Anyone know what this is?

I tried attaching a photo, but it wouldn't allow me.

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Oct 13th 14 2:56 am
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Re: Gunk in teapot?

by tingjunkie » Oct 13th 14 2:56 am

Welcome to the forum!

Very bizarre situation you got there. Is the inside surface quite shiny? If it's enameled, it should be. Can you shine a light inside and make sure there's not a spot missing its enamel? Even so, I can't imagine why raw iron would turn tea black. What happens if you leave plain boiled water in it for an hour?

Ultimately, I'd try to get a refund ASAP. That shouldn't happen.

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Oct 13th 14 1:02 pm
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Re: Gunk in teapot?

by Fuut » Oct 13th 14 1:02 pm

Tingjunkie's advice is sound. It shouldn't mess up and dirty the water or tea inside. You shouldn't drink it before making sure you know whats going on.

Also if you can't add the photo here (by upload attachement) its probably higher than 1000 pixels or wider than 640 pixels. You can try to upload it somewhere and add it by [.img]link[./img], without the dots:)

Oct 13th 14 1:25 pm
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Re: Gunk in teapot?

by .m. » Oct 13th 14 1:25 pm

Just 2 remarks:
- tea+rust makes a very dark stains, darker than just tea or rust alone (i used it to tint wood in the past).
- some (cheap) cast-iron pots have some sort of matte black paint on the outside, that can often be scrubbed and washed out, but of course this shouldn't affect the tea inside.
Good luck returning the pot.

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Oct 14th 14 2:46 am
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Re: Gunk in teapot?

by kyarazen » Oct 14th 14 2:46 am

sounds like the enamel coating's coming off and the tea is reacting with the exposed iron. :shock:

Oct 31st 14 8:01 am
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Gunk in teapot?

by sainthurricane » Oct 31st 14 8:01 am

Oct 31st 14 8:06 am
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Joined: Sep 9th 14 6:59 am

Gunk in teapot?

by sainthurricane » Oct 31st 14 8:06 am

Hey fellas, thanks for the replies. Here is the pic. I'm pretty sure the inside is enameled,it's shiny and Iwachu teapots are enameled inside.

It's still doing this, even with high-grade tea. I guess it will just be a decorative piece...

Feb 19th 18 1:49 am
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Re: Gunk in teapot?

by Tatsurou » Feb 19th 18 1:49 am

Hi from Tokyo.

The topic is dated by over 3 years but I'm posting for the record.
I checked Iwachu's website, which comes only in Japanese, and found this:
- Tetsubin Kettle: Cast iron, no coating inside for the purpose of adding iron to the boiled water. To be placed on direct heat.
- Tea Pot: Glass enamel coating inside the pot and the lid. Not to be exposed to direct heat.

Now, from my experience of life in Japan, generally speaking, Tetsubin is used for boiling water only and Tea Pot is for brewing tea. (except when making herbal tea for medicinal use where the taste and color is not an issue but the efficacy with added iron is the purpose of using it)

Looking at the attached photo, by the size of it, I'm under the impression that what you got is a Tetsubin. What looks like enamel inside must be protective coating to keep it from rusting during shipment and while on display at shops.

When tea is brewed in Tetsubin, once again it's not a usual practice, the iron in the water reacts with the tannin in tea, making the tea black by oxidation, and the oxidized tannin becomes separated from water through that process and will appear as residual, hence gunk in the tea. Similar blackening of tea occurs when tea is brewed with "hard water", typically mineral rich water often sold in bottles.

My advice will be to use proper pots for boiling water and brewing tea. The shop clerk that sold it to you would have known that and should have given advice as such.

As for the initial preparation of Tetsubin and maintenance thereafter, if needed, I'll post separately.

Best regards,

Jul 5th 18 4:30 am
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Re: Gunk in teapot?

by teapotluck » Jul 5th 18 4:30 am

I'm a newbie, but in my research I've found the following:

Well made tetsubins will have a blue gray smooth finish inside, but that is not enamel. It's the way the pot is finished...

Tea has tannins, and acids that interact with the iron in the pot, and this is why iron kettles or tea pots are desirable.

I found a rusty tetsubin in an antique store, and I've been researching what to do. Apparently tea leaves create a black coating on the inside of a pot that protects the pot from rusting.

You can take it back to the store, maybe they will reassure you that the pot is fine, it isn't doing anything unusual.

A lot of sites recommend wiping the pot out after using it. so, maybe wipe out the pot and get up the "free" black gunk, but basically it may be just fine.