There are a few reasons why cast iron kettle is coated.

(i) Prevent the Kettle from Leaking

The structure of cast iron is very porous. The present of some minor holes is inevitable. Usually kettle has minor leakage. Every finished product is inspected and confirmed the position of leakage and the leaking point is spotted and sealed using natural lacquer called Urushi (漆). Urushi is the sap of tree called Urushi. This is the most traditional coating material in Japan. Some wooden furniture coated with Urushi that salvaged from the sunken ship found in deep ocean was remaining intact. The Urushi coating effectively protects the wood from salt-water. Urushi performs like resin when it is applied at high temperature. It hardens and can hardly come out. At the bottom of kettle, the Urushi treated spot appeared in black color while other area remains in blue-gray color.

(ii) Painting Urushi as base coating

Urushi is also applied on the external surface of kettle as a base coating. When the kettle is heated up to 300-400 degree C, the urushi is applied. On the top of base coating, another layer of coating in black or brown color is applied. This coating material is made of Urushi mixed with sand iron. The different brand uses different color and the production technique is kept secret.

(iii) Anti-rust

Occasionally some artists like to paint urushi inside the kettle in order to protect the iron from rusting. However this coating will lessen the reaction of iron with water, yet some people prefer this since the kettle is hardly becomes rusty.

There are 2 different types of handle, hollow and solid. The making of handle is completely different from casting. Handle is made by forging while kettle is made by casting.

(i) Hollow Handle

The hollow handle is used for super high-end kettle. This type of handle is made of iron plate. It is rolled and forged into the intended shape. The handle has a few holes which is called insect bite. This is a fashion and also has a function to cool down the handle. The insect bite hole is the symbol of the hollow type handle. The kettle made with hollow handle is much more expensive than solid handle.

(ii) Solid Handle

The solid handle is used for low to intermediate model. The solid handle is made of iron bar. It is forged into the intended shape. Majority of hand-made kettle in the market has a solid handle. The production cost for solid handle is much cheaper than hollow type. Nowadays we use either gas cooker or IH cooker for heating kettle. The handle never gets hot even if it is made of solid material. As a matter of fact, the type of handle is a fashion and it is the major factor in determining the price and superiority of kettle.

Traditionally cast iron tetsubin was heated by charcoal fire. The charcoal fire does not generate moisture and it will not cause rust at the bottom of tetsubin. If using a gas cooker, it generates Carbon Dioxide and water when it is burning. In a long run, the bottom part of iron tetsubin becomes rusty. However it is a very natural change. The rust only appears on its surface and it does not cause any harm to the material. If you do not like it, you can apply green tea on it to reduce the rust and it will turn to dark color. Somehow many Japanese customers rather appreciate the change of color in the long run. It is kind of Wabi-Sab. It will form very classical color which makes your tetsubin very identical.

Please note that the induction heater can not be used for the small kettle which the diameter of bottom area is less than 80mm. The manufacturer recommends not using too strong heat on induction heater. This is because the induction heater gives very localized-heat. When it is heated on the induction heater, the iron locally expands and when it is cooled down, it shrinks. The intense heat will give stress to the metal and the kettle cannot last up to 50 years of usage. In particular, sand cast iron is more brittle than normal cast iron. It must not be heated with intense heat on the induction heater.

 

 

Usually tetsubin has 2 circular spots at its bottom part. It is the trace where “katamochi” was located. Katamochi is the 2 nails that used to fix the internal mold (nakago) during casting. Thus tetsubin has 2 holes on its bottom. These holes are sealed with material that is prepared mixing urushi with iron sands.

When cast iron tetsubin is heated on induction heater, these 2 spots tend to be over heated. Due to the nature of the material used on these spots, it gets hotter than cast iron. Therefore it is necessary to start heating at very low output if induction heater is used.

 

When start using the cast iron kettle, please take note of the following:

• 1)When using the cast iron tetsubin for the first time, pour in water, place it on the heater and boil the water. Once the water is boiled, pour off water from tetsubin, and repeat it with fresh water for a few more times. This will get rid of the interior odor of the new tetsubin. If you use induction heater, you must set the heater with lower output until entire tetsubin is heated up. If tetsubin is heated with stronger fire from the beginning, it causes stress to the tetsubin.

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• 2)  After boiling the tetsubin for a few times, if the interior odor of tetsubin still remained, place ginger or tea leaves and boil with water. These food stuffs contain a lot of antioxidant which also protect the iron from rusting.
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• 3)Each time right after finish using the tetsubin, boil the remaining water and pour out the excess water from the tetsubin, and remove the lid. The remaining heat will evaporate any excess water. Please do not heat tetsubin without water inside. It will damage the tetsubin, especially the 2 urushi sealing points (black spot) at the bottom will come off. As a result, it causes leaking of water and sometimes crack may occur.
• 4)Whenever you replenish fresh water to the tetsubin, please make sure that there is water left inside tetsubin. Never add cool water to a tetsubin that has been heated up. If cool water is added when a hot tetsubin is empty, it causes damage to tetsubin due to sudden shrinkage of the material. If there is water remained inside tetsubin, the temperature on the surface of tetsubin will never go higher than 100 degree C. However the temperature keeps going up higher and higher if no water is left inside while tetsubin is heated.

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• 5)After using the tetsubin for a few days to a week, you may observe red spots at the bottom part of the tetsubin. It will definitely appear on new tetsubin. This is normal. It is the reaction of minor minerals remained on the surface of tetsubin. Please do not touch it, wash it or scrub it.
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• 6)In about 2 week’s time, you may observe some white spots at the bottom part of tetsubin. This is also normal. This is a layer of natural minerals, such as calcium carbonate, that is built up from use. Never try to remove it as this layer also contributes in improving the taste of water and will help to prevent rust. From my observation, the old tetsubin that is kept in good condition always has a layer of white scale as thick as snow.
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• 7) Do not wash or rub the inside or outside of tetsubin with a sponge, brush or detergent.
• 8) Do not leave any water in the tetsubin for a long period of time.
• 9) If accidentally keeps water inside the tetsubin for more than a day, the tetsubin will partially get rusted. However never try to remove it with physical strength, scrub it or wash it with detergent. If rust appears inside the tetsubin, place some green tea or green oolong tea leaves and boil for a while, switch off the heater, let it naturally cools down and leave it for a few hours. Thanks to the antioxidant from tea leaves, the rusted part will be reduced and color will turns dark. If rust appears on external surface or cap, heat up the tetsubin, and then apply tea on its surface. You can soak a piece of cloth with tea, lightly squeezed out excessive water before apply it on the hot surface of tetsubin. Repeat it over and over again as it instantly evaporates tea.
• 10) The surface of tetsubin can be polished with a soft cloth which has been soaked with tea. This will keep the glossy outlook of tetsubin.
• 11)Medically, rusted iron is safe for health. Scientifically, rust is caused by oxidation, which occurs when oxygen contacts with iron for a long time. The oxygen combines with the metal at atomic level, forms an iron oxide and weakens the internal bonding of the metal. In Japan, some traditional cooking is purposely added with rusted nail in order to get an attractive color on bean.

 

 

Q1: What is the Kyoto Style Cast Iron Kettle?

There is a noticeable number of Kyoto style tetsubins in Asia market such as Kibun-Do (亀文堂) and Ryumon-Do (龍文堂). Ryumon-Do (龍文堂) is the very old workshop started in year 1764. It was the first brand who invented wax mold in casting the iron tetsubin. Taking the advantage of wax mold that enables the making 3 dimensional designs, Ryumon-Do’s product has very gorgeous carving on its surface. The Kibun-Do (亀文堂) was set up in Shiga prefecture by the student of Ryumon-Do. Both workshops produced a number of products in the history, yet disappeared.

Many people were told and believed these two workshops were the most prestigious and high-end brand in Japan as these products are very common in Asia. Nowadays these 2 brands always appear in the auction. These products are purchased by Taiwan Company, reconditioned and introduced to the market. Due to the gorgeous carving and silver inlay, people spontaneously take it as a high-end product. In fact, these products are just one of the styles. Usually Kyoto style kettles reaches the end-users at shop after it has gone though too many channels, therefore the price is pretty high.

Q2: Is Old Kettle Better or New Kettle Better?

A number of tetsubin being sold and claimed to be antique piece were often covered with a thick layer of rust in the interior. In fact, used tetsubin seldom gets rusty up to that extent. The tetsubin in such conditions showed that it was not correctly used for a long time or purposely made in such a condition in order to imitate the appearance of an aged tetsubin. Usually under the normal usage, only a thin layer of rust stays on the surface. The excessively rusted interior no longer retains ferric, but ferrous. In addition, it is doubtful that terribly rusty surface has the same porosity. It would give a very different effect in taste compared to the original condition. In this regard, it is not true that old tetsubin performs better.

However there is an exceptional case. There is very limited number of old tetsubin which performs pretty well. In the old days, the casting technique was different. During the Edo era, all tetsubins were made of Satetsu (Sand Iron). As I mentioned earlier, satetsu tetsubin gives a good effect in taste and flavor thanks to its porosity. However those antique satetsu tetsubins are very brittle. Most of them cracked after long period of usage. We could hardly find an authentic satetsu tetsubin that is made during Edo era and remained until today. There is less reason to look for an old tetsubin considering that there are existing brands producing very good quality and also satetsu tetsubin is being continuously produced until today.

Q3: Is the old kettle has a higher value in the market?

The old tetsubin tends to have a very thick layer of scale inside. It was built by the previous user. People appreciate it as they believe it changes the taste more effectively. However the scale must be formed with your own water. In fact, the scale that is formed earlier by another person does not give a positive effect. As a conclusion, it is wise to consider a new model rather than a used model, unless it is for display or decoration purpose.
As I mentioned earlier, old tetsubin does not give a higher value due to its condition, unless it’s a good design made by famous artist and was kept in a very good condition, it is highly valued as an antique piece. At the same time, there are a lot of hidden risks; sometimes unaware leaking or crack is found on old tetsubin. We suggest customer to consider high-end model made by famous artist in modern day. Since you know its origin and the artist better, you can foresee the value of it in future rather than gambling with antique model that its origin information is ambiguous.

Q4: How to know if it is a "kettle" or a "tea pot"?

In general, most of the hand-made cast iron tea ware is a “kettle”. The majority of tea pot is commercially made in mass production process. The major difference is as follow.

• 1) Tea Pot has a strainer, while kettle does not have.
• 2) The internal surface of tea pot is glazed, while kettle is not.

Q5: Is it OK to place cast iron tea pot on fire?

Basically the answer is “No”. The cast iron and glazing material will expand when it is heated. But the ratio of expansion is different between these materials. Sometimes it causes crack on glazing material. In addition, there is always a risk of heating the empty tea pot. The moment the cast iron tea pot is heated without water inside, the glazed material will melt as its melting point is much lower than cast iron. This question is referring to the "teapot". For cast iron tetsubin, of course it is fine to place it on fire.

 

Q6: Can HOJO repair the Kettle if it is broken?

Most of the damages can be repaired, e.g. if the tetsubin becomes very rusty, there is a minor hole, cap becomes dented or lost or some parts are cracked. As HOJO is directly dealing with the manufacturer, we are able to provide professional service after sales. If repairing is required by manufacturer, we need customer to bear the shipping cost and repairing fee. We do not charge any profit on the repairing work.

 

Q7: Is tetsubin good for health?

Recently the medical effect of tetsubin has drawn the attention of people. According to the Ministry of Health, Labour and Welfare of Japan, the necessary amount of iron that our body requires is about 10mg per day for ordinary people and 20-23mg per day for a pregnant woman. Using tetsubin, it provides ferrous ion which is easier for our body to utilize compared to ferric ion. The iron is the main component of hemoglobin in red blood cells. The function of red blood cell is to supply oxygen for respective organs in our body. Sufficient supply of oxygen keeps our health very well. Having exercise, massage or acupuncture is good for our health for the same reason that it improves blood flow and supplies our body with oxygen. In particular, iron intake contributes to the improvement of immune system, as well as improves liver function, constipation problem, beneficial for low blood pressure patients and even for those with infertility problem.

 

Q8: Is it OK to heat up tetsubin until it’s completely dry?

Tetsubin MUST NOT be heated when there is no water inside. The temperature of tetsubin goes higher than 100 degree C if there is no water inside. If water is remained inside, the temperature of tetsubin will be less than 100 degree C no matter how much it is heated. Once the temperature goes higher than 100 degree C, it burns the 2 urushi spots that are located at the bottom of tetsubin. As a result, it causes leaking and in the worst case, it causes crack of tetsubin. Sometimes we receive tetsubin from customer claiming that tetsubin was leaking. If we examine the condition of the 2 urushi spots, we will find out whether or not it is caused due to the excessive heating. If tetsubin is heated without water inside, the 2 urushi spots are peeling off.