Grey powder inside my tetsubin

[Oni]

I wanted to ask a question from the veteran tetsubin owners, what is that grey powder that keeps forming on the inside of my tetsubin?
When I bought it is had a thick powder coating, I wiped it out with a paper towel, I boiled water 3 times and I started using it, even after a year, after using it for a tea session, when it has dryied I stuck my finger to the wall of the tetsubin and it has a thin grey powder coating, could it be that the activated iron surface is reacting with air and moisture and it forms a kind of white oxidation, in form of a powder.
P.S. I always dry my tetsubin before putting it away in my drawer, and I use clean water with it.

[AdamMY]

It sounds like it could be Mineral deposits from the water. Does something similar happen in any other kettles you may use?

Although while I am not a Tetsubin owner, I do believe people want the build up of minerals on the inside of a Tetsubin as I believe it can help prevent rust.

[MarshalN]

If it's forming from you using your tetsubin, it's coming from your water. I wouldn't worry about it. What kind of water are you using?

[rdl]

P.S. I always dry my tetsubin before putting it away in my drawer, and I use clean water with it.

i don't use or own a tetsubin but this question is related to the OP and something i've wondered about.
it is my impression a tetsubin is to be in constant use, so is the repeated wet and dry (storage) a problem, possibly causing the powder problem and other rust problems?
oni - i hope you'll be able to solve this, good luck!

[Oni]

I am using my tetsubin daily, sometimes twice, I am drinking japanese greens this month, but I used it constantly a year long, and I observed red dots of rust inside, plus this powder.
I am using volcanic spring soft water, 70 mg / 100 ml water hardness, I am using the same brand of water for 4 years.
This grey powder is always present, today I rinsed out my tetsubin 3 times, I had a tea session, and after it had dried and cooled I rubbed my finger inside it has this very fine powder.
I will try to take some photos tomarrow.

[rdl]

i don't think i was clear when i wrote contant use. i was questioning should a tetsubin be constantly filled with water on a heat source, being refilled with cool water as needed after heated water was poured out, rather than filled with water, heated, emptied, cooled and put aside, and sometime later refilled and heated...etc?
is that correct and/or related to the gray powder problem?

[MarshalN]

I am using my tetsubin daily, sometimes twice, I am drinking japanese greens this month, but I used it constantly a year long, and I observed red dots of rust inside, plus this powder.
I am using volcanic spring soft water, 70 mg / 100 ml water hardness, I am using the same brand of water for 4 years.
This grey powder is always present, today I rinsed out my tetsubin 3 times, I had a tea session, and after it had dried and cooled I rubbed my finger inside it has this very fine powder.
I will try to take some photos tomarrow.

I think it's mineral deposits. You haven't had this tetsubin for four years, have you?

Rust is pretty normal. Expect rust.

[Oni]

i don't think i was clear when i wrote contant use. i was questioning should a tetsubin be constantly filled with water on a heat source, being refilled with cool water as needed after heated water was poured out, rather than filled with water, heated, emptied, cooled and put aside, and sometime later refilled and heated...etc?
is that correct and/or related to the gray powder problem?

A chagama at a teahouse, like the one we see on maiko`s site, I assume it functions all day long, but those smaller ones used in homes cannot function all day long, even though I read that they heat their water for soups in a tetsubin, I use it for every kind of tea, I boil water, and I refill it only when it has hot water inside, you just pour the cool water in the hot water, this way it cools the wall of the tetsubin slower, and the risk of cracking is reduced, never pour cool water in a hot kettle, this applys to ceramic kettles too.

[Oni]

I am using my tetsubin daily, sometimes twice, I am drinking japanese greens this month, but I used it constantly a year long, and I observed red dots of rust inside, plus this powder.
I am using volcanic spring soft water, 70 mg / 100 ml water hardness, I am using the same brand of water for 4 years.
This grey powder is always present, today I rinsed out my tetsubin 3 times, I had a tea session, and after it had dried and cooled I rubbed my finger inside it has this very fine powder.
I will try to take some photos tomarrow.

I think it's mineral deposits. You haven't had this tetsubin for four years, have you?

Rust is pretty normal. Expect rust.

How long will it take for it to make a fur, I am using it for a year, but it still looks like new.

[MarshalN]

If you want to artificially make it -- just fill it with water (higher mineral content the better) and let it boil dry