Care for your Tetsubin!

Finally something important I feel I can contribute to the tea world — my poor habits of caring for my iron kettle (tetsubin)

I am starting to develop some bad habits when it comes to caring for my tetsubin. When you boil water inside the kettle, the water will regulate the temperature so that it doesn’t exceed 100 degrees. When it is time to empty the kettle, the method is to bring it to boiling point, pour out the water and open the lid so that the heat from the kettle can evaporate all the remaining moisture inside and quickly dry the interior.

I am getting accustomed to putting the kettle on a burner and walking away to do some tasks eventually returning to it to empty the contents. This is about the 5th time I’ve walked away and the water inside has boiled off. If there is nothing to regulate the heat it can quickly reach some scorching hot temperatures. My worst case of this was probably around 15  minutes of heating without water inside.

There is a smell created when it gets so hot which is really nauseating for me. The problem is that I don’t know if it’s the smell of the lacquer burning/melting, the smell of the calcium buildup on the interior of the kettle burning, or just the aroma of extremely hot iron.  Whatever it is, it will change the flavor and aroma of the water. The water will take on a ‘hot metal’ or ‘burned’ aroma and metallic bitterness.

The thing is, I’ve had this kettle for years and this issue of it superheating is rather new because I used to be a lot more careful with it. There is a silver lining to all of this: with already 5 instances where it has happened, I can shed some light on how I’ve found I can remedy the situation.

I think its logical to infer the nasty burned aroma and flavor is caused by the burned calcium carbonate buildup inside the kettle. It’s a shame to remove it as the carbonate scale helps to prevent rusting of the interior, but it must be done to return to a neutral flavor. The small information booklet that came with the kettle, and nearly every ‘care and use guide’ I’ve read about the kettles mentions that you should never scrub the inside of the kettle. So I’ve never done that, but I have done other things!

The last time this happened I boiled the kettle in a large stockpot  of oolong tea (the tea becomes quite black). Once the tea cooled down I removed the kettle, rinsed it off with water, filled it with fresh water and boiled it. It helped a bit, but not really as much as I was hoping. This technique is great for darkening the oxidized areas of the pots exterior which rusts from heating it using compressed gas burners (they create water vapor when they burn)

This time I am doing an experiment. I will be bringing a full kettle of filtered water from cold to a boil and emptying a tea cups worth for tasting while  dumping the rest and repeating the process until I don’t sense the burned/metallic aroma anymore.  I’ll see how many kettles of water I need to go through to return to neutrality.

Ultimately I am not worried about returning to neutral because as I stated this is not the first time this has happened and I’ve managed to fix the problem every time so far. What I am worried about is the melting of the lacquer on the bottom. Apparently there are pin-sized holes on the base which get sealed with urushi (a type of natural lacquer) during the manufacturing process. While they are heat resistant up to a point, eventually they would melt.

There are very fortunately no signs of that having happened yet as no water is leaking through the metal. Although I am noticing 2 spots on the bottom of the kettle which seem to be ‘flaking off’. I somehow doubt these are the urushi spots and that it’s just a coincidence that there are 2.  Those spots coincide with dark red rust marks on the inside. While this is a worrying sight, somehow I don’t feel it’s related to the problem we are discussing but rather my choice of heating method which is unfortunately unavoidable.

Let’s talk about the water. For the record starting this at 11:45pm.

Cup A) Standard filtered water, unboiled
Cup 1) First time off the ‘superheated kettle’. Definitely visual difference between the filtered water and this. There is a light brown tinge. It definitely doesn’t taste healthy. I’d go on the record to say it tastes burned, and like hot metal. I’d say it has toxic qualities to it.
Cup 2) honestly… the flavor is pretty netral. The ‘toxic’ aspect is not there, I don’t get any unusual flavors.
Cup 3) same
Cup 4) same
The aroma of hot metal is still very apparent when opening the emptied kettle and smelling the steam.
Cup 5) didn’t bother drinking, I feel the flavor is normal, its just the smell of the kettle now
When I poured out the 5th the metallic aroma is nearly gone, it smelled like a slightly unusual steam (but not metallic), I feel that once more should do it.
Cup 6) didn’t bother drinking,
When I poured out the 6th the metallic aroma was actually a bit stronger than the 5th? Strange.  Although I said it last time I feel that once more should do it.
Cup 7) Still a little bit metallic in the smell
Cup 8) Still a little bit metallic in the smell
Cup 9) Seemingly normal
Cup 10) Seemingly normal
Cup 11) Normal

So it only took about 2 1/2 hours to fix the problem, not a big deal. Now that the flavor has returned to normal, I can finally start to worry about whats going on with the bottom! \o/