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Testubin: How to Use and Care for Your Japanese Tea Kettle

Posted by Boyka Mihaylova on

In a previous blogpost we uncovered the secrets behind Tetsubin's history and production. Today, we are looking on the practical side of things. We'll provide you with step-by-step instructions on how to use your Japanese tea kettle. We'll also answer some of the most (and some not so) common questions that may arise in the process. Ready?


How to use a Tetsubin: A Step-by-Step Guide

Using a Tetsubin, the traditional Japanese tea kettle from cast iron,  involves a specific procedure to maintain its integrity and enhance its tea-brewing capabilities. Here's a step-by-step guide to properly use and care for your Tetsubin:

Initial Rinse: Begin by rinsing the kettle with water or lukewarm water. Avoid using detergents or sponges, which can damage the kettle's interior.

Boiling Water: Fill the kettle with water to 70-80% of its capacity to prevent boiling over. Heat the water over low to medium heat. If needed, adjust the lid slightly or remove it to avoid overflow.

Pouring Water: Once the water has boiled, if the handle is hot, hold it with mittens or a cloth, and pour the water out slowly.


The heated iron kettle becomes very hot, so use a trivet mat to avoid damaging the table.


Post-Use Drying: Empty the kettle completely and place it back on the stove on very low heat to evaporate any remaining water. This should take about 30 seconds to 1 minute.

Prolonged exposure to extreme heat without any water inside will damage the kettle. If you have heated the kettle for a long time without water, be careful not to pour cold water into it (which will burn you with steam) or place it on a wet cloth as it can cause cracks. Leave it as it is to cool down.

Cooling and Wiping: After evaporation, turn off the heat and allow the kettle to cool. Wipe any remaining droplets off the kettle and lid with a soft cloth.

By following these steps, you ensure your Tetsubin remains in optimal condition, ready to brew the perfect cup of tea every time.


japanese tea kettle cast iron


Caring for your Tetsubin: Tea dyeing

Tea dyeing is an effective method to maintain the interior of your Tetsubin. It utilizes the tannin in tea leaves to react with and neutralize buildups of rust and dust. This process not only prevents further rusting but also addresses issues like rust coloration of boiled water or the presence of strong metallic odors. Here's how to do it:

1. Preparation: Depending on your Tetsubin's size and the extent of rust, measure the required amount of tea leaves. Use the ratio of approximately 1g:20-30ml. However, this is only a generally suggested ratio. Each kettle and its particular condition is different, and you have to make your own judgment. The tea you are using shouldn't be expensive. The important factor is that it should contain lots of tannins. Opt for Black, Dark Oolong, or Raw (Sheng) Pu-erh teas. 

2. Brewing: Place the tea leaves into the kettle, add water, and heat. Once boiled, turn off the heat and let it steep for approximately 10 hours (or leave it overnight).

3. Cleaning: Discard the darkened water and tea leaves after steeping, then rinse the kettle lightly.

4. Drying: To finish, dry the kettle on very low heat without water until completely dry.

By repeating this process 1 to 3 times, you'll notice a reduction in water turbidity and metallic taste. For external rust spots like the lid's back, spout, or handle, gently rub with a cloth soaked in tea. Be mindful of potential staining on light-colored cloths. This simple, natural method keeps your Tetsubin in prime condition, ensuring a pure tea flavor.


japanese cast iron tea kettle

Still have questions? 

Here are some of the most common questions about using and caring for your Tetsubin answered.

Rust appeared inside the iron kettle immediately after usage. Is it okay to use it as it is? 

The inside of the iron kettle is prone to rust. It is a proof that iron elutes, so please use it with confidence. If you try to scrape off the rust by force, you will ruin the thin oxide film on the inside and damage the vessel. 

The rust spread in the kettle's interior, turning the hot water reddish-brown and cloudy. It also has a metal smell. Is it okay to drink? What should I do to clean it? 

A reddish-brown turbidity indicates an excess of iron. There is no harm in drinking it, but if the boiled water or brewed tea doesn't taste good, try "tea dyeing". 

The interior, the spout, and the back of the lid have become white. Should it be washed off? 

It is probably due to limescale residue. Limescale is harmless for cast iron kettles. It also prevents rust, so be careful not to scrape it off by force. You can switch from mineral water (hard water) to spring or purified water (soft water). 

The inside bottom of the kettle has a blue-greenish glow. Is it okay to use it?

Sometimes, you may notice a thin oil film on the inside of the cast iron kettle or the water's surface. This is due to the iron reacting with the water and is generally harmless. 

Does the outer color of the iron kettle fade with usage?

Due to the heating on gas or induction, the outer color gradually changes from the bottom. If you continue to use the kettle on high heat, the color will fade quickly, so it is recommended to heat it slowly over low to medium heat. In addition, the color of the handle, the spout, and the back of the lid, which are exposed to steam, will change, and occasionally rust might appear. It is safe to use if you clean it regularly. Enjoy the changes over time as part of the wabi-sabi philosophy. 

Is it okay to leave the kettle on the stove? 

It's fine, as long as there is water inside the kettle and the stove is on low heat. Boiling the kettle without water for a long time will damage the thin oxide film on the inside. It will also deteriorate the outer color and cause premature aging. 

Can I use the Tetsubin with an induction cooktop?

Yes, you can. However, strong heating accelerates deterioration over time, so use it over low to medium heat (the same applies to all heat sources, such as a gas or electric stove). 

When boiling water, black residues form on the bottom of the kettle. Are these pieces of iron? Is it okay to drink it? 

These are thin scales of the inside oxide film. In rare cases, the oxide film may peel off due to water pressure. The film is light gray, but it becomes black when peeled off. Also, if you have done "tea dyeing" or brewed tea, the fine tea powder may dry out and fall into the boiling water, coming out as black residue. There is no harm in drinking the film or the remains of the tea powder. It will gradually disappear as you use the kettle. 

How do I store the cast iron kettle when not in use for a long time? 

 First, boil the empty kettle until all the water evaporates. Set aside (always use a mat or plank) and let it cool naturally. After cooling down completely, wrap it in a newspaper and store it in a dry and cool place. 

The kettle has an ink smell that doesn't go away even after boiling water in it. What should I do?

The ink-like smell comes from the outer paint. You may notice this smell for a while after the initial usage, especially when heating it. It will eventually disappear. Regular usage, as well as boiling water without the lid, will accelerate the process.

How do I know if my ironware is an iron kettle or a teapot? 

Check the inside of your kettle's body. If it is uncoated, gray-black in color, you have a tea kettle. If it is glazed (ceramic), it is a teapot.

While cooking, a drop of oil fell into the Tetsubin iron kettle and formed a stain. How can I get it off?

Due to the uncoated interior, oil stains cannot be removed. When not in use, we suggest storing your Tetsubin away from the cooking area.


Our journey through the world of Tetsubin has offered us a glimpse into its history, craftsmanship, and role in Japanese tea culture. These cast iron kettles are a part of Japan's rich tradition and dedication to the art of tea. The Tetsubin cast iron kettle enhances both the water quality and the overall experience of tea drinking, making it an exemplary piece of practical beauty. We are invited to appreciate these traditional vessels more deeply, from admiring their elaborate designs to mastering their care and everyday usage. The Tetsubin transcends its functional use; it's a cultural symbol, enriching our tea experiences and connecting us to Japan's artistic and philosophical legacy.