Tetusbin and Scale

[JustinW]

From what I have read about tetsubins, you are not supposed to wash them at all, and this leads to scale build up which is supposed to improve taste. If that is so, why is it that we always descale our kettles and such? I find this contradicting.

This is a quote from here:

In about 2 weeks, you may observe some white spots on the bottom of kettle. This is also normal. This is a natural mineral layer build up from use, such as Calcium Carbonate. Never try to remove it as this layer also contributes in improving the taste of water and will help to prevent rust. The old kettle that kept in good condition always has a white scale as thick as snow.

Also on a random side-note:
Right now I boil fresh water for each infusion, and I was thinking it would be nice if I could just boil one large batch and keep it warm. Does anyone do this, and does it sound realistic? How would this kettle work for that? Also, how well does the utilitea hold heat? Would it work for this?

[chingwa]

Well, I am no expert. but the way I see it is that am using a tetsubin for a specific reason and that is too imrove the taste of the tea/water. all the advice I've been given says never wash or touch the inside of the tetsubin... this from people much more intimate with tetsubins than myself.

I think descaling of a stainless steel kettle would carry dfifferent considerations than descaling a tetsubin.

[wyardley]

Right now I boil fresh water for each infusion, and I was thinking it would be nice if I could just boil one large batch and keep it warm. Does anyone do this, and does it sound realistic? How would this kettle work for that?

I have that kettle (from another source), and it will keep the water between the temperatures it's programmed to if you leave it on auto.

This is a controversial issue which (like most things about tea) there's not much agreement on. I think most would agree that it's not wrong to make a single batch for each infusion, but without a really small kettle and a strong fire, it's not usually practical.

Some will tell you to always use up all your water before putting in fresh water (and, I assume, to reboil as necessary if the quantity is more than you use for one infusion); others will tell you that reboiling the water too much will remove too much oxygen and that you should add fresh water to the existing water to refresh it (before re-heating). I usually do a combination of the two approaches... I'll bring the water to a low / medium boil, and use that water once or twice (reboiling as necessary), then add more when the water level starts to get low.

[wyardley]

From what I have read about tetsubins, you are not supposed to wash them at all, and this leads to scale build up which is supposed to improve taste. If that is so, why is it that we always descale our kettles and such? I find this contradicting.

This is a quote from here:

In about 2 weeks, you may observe some white spots on the bottom of kettle. This is also normal. This is a natural mineral layer build up from use, such as Calcium Carbonate. Never try to remove it as this layer also contributes in improving the taste of water and will help to prevent rust. The old kettle that kept in good condition always has a white scale as thick as snow.

Keep in mind that this is one opinion. I haven't heard one way or another, but my guess is that there are competing opinions on this. And, more to the point, there may be other reasons that it's undesirable to descale iron kettles. For one thing, I don't think you'd want to use an acidic substance like vinegar on iron. I don't know about those descaling tablets and whether or not they're suitable for use with cast iron.

So while I would definitely descale a stainless steel kettle that had a lot of buildup, I don't know if I would on a cast iron kettle or not.

[Intuit]

http://www.springhillatcanfield.com/taste.html

Mineral deposits do not add desirable flavor qualities to tea making, guaranteed. The exception might be carbonation degree of the source water, as it can shift the mineral chemistry, pH and resulting complexes formed with tea flavor components.

If you like scummy/soapy water that may add favors or alter the chemistry of the resulting liquor, go for it!

The suggestion that a thick layer of mineral deposit can act as corrosion insulator may hold true, except that I've seen evidence to the contrary, in large water supply conveyance mains (pipes) that failed due to corrosion. The pipes featured a thick concentric deposit of minerals that reduced the active flow interior diameter to a tiny fraction of the original pipe ID. The corrosion occurs because the mineral is highly conductive and hydroscopic, that is, it attracts and holds water deep within the crystalline deposit layers and can become charged due to corrosion chemistry. If the corrosion inhibition is a function of salt barrier effect, I wouldn't think it very effective, because even months after a large slug was cut from the aforementioned pipe for use as a demonstration aide (teaching university water quality courses), the salt deposit was 'wet' due to atmospheric humidity and retained molecular (bound) water.

[Intuit]

Commercial descaling of cast iron requires electrolytic hot baths. Most of the descaling solutions are highly acidic and probably aren't suitable for a kettle.

http://www.kamco.co.uk/FX.htm

Some descaling solutions leave a passivating phosphate film on the metal.

However, there maybe descaling solutions for home use that are safe for cast iron., for cookware and kettles. I found a web page that suggests using a boiling white vinegar solution soak to safely remove scale buildup from cast iron.

http://www.fantes.com/kettles.html

It also says that a deposit of minerals will delay rusting (in this case, of humidifier kettles).

[JustinW]

Keep in mind that this is one opinion. I haven't heard one way or another, but my guess is that there are competing opinions on this. And, more to the point, there may be other reasons that it's undesirable to descale iron kettles. For one thing, I don't think you'd want to use an acidic substance like vinegar on iron. I don't know about those descaling tablets and whether or not they're suitable for use with cast iron.

So while I would definitely descale a stainless steel kettle that had a lot of buildup, I don't know if I would on a cast iron kettle or not.

I figured it wouldn't be a good idea to descale the cast iron kettles for reason of ruining them. I was inquiring because several people in this thread said the water boiled in the cast iron improved the taste of tea, but I always figured the scale(which you will eventually have in the iron kettle) make crappy water.

@Intuit
Thanks for the interesting read.

[snafu]

I was inquiring because several people in this thread said the water boiled in the cast iron improved the taste of tea, but I always figured the scale(which you will eventually have in the iron kettle) make crappy water.

A simple blind taste test of water boiled in a tetsubin vs. that from another non-iron kettle is pretty revealing. I've done this more than once, both to satisfy my own curiosity and to convince skeptical friends, with both a clean newish tetsubin and an older one with a fair amount of carbonate build-up. To me the difference in flavour is quite noticeable, and objectively most people I've tried this with can pick out the tetsubin water. I think it is an improvement in taste - it seems sweeter, lighter somehow. Tradition has it that the reason for this is that trace amounts of iron are present in water boiled in a cast iron vessel - this is also one of the reasons traditionally that iron-rich shudei clay from Tokoname is promoted by Japanese tea experts. I don't know enough about the chemistry of iron in tea/water to accept or reject that explanation, but I won't doubt my taste buds unless I have a good reason to.

I'm assuming you are referring to an unlined true tetsubin kettle and not one of those enamel coated tetsubin-shaped tea pots.

[JustinW]

Interesting. I'll just have to try it myself if I ever get a chance. And yes, I was referring to the real unlined tetsubin.

[joyfulwoogie]

After each tea session, I let the testsubin dry out with heat. Then before use, I rinse the tetsubin for any unattached particles from the previous heat drying. Sometimes I see chrystal calculm particles. In about a year or so, I am starting to get a good calcium build up.

[nada]

Mineral deposits do not add desirable flavor qualities to tea making, guaranteed.

I've found this to be the opposite. Tasting water from 10-20 different antique tetsubins, the water from ones with mineral deposits inside was sweeter and better for tea. Too many minerals gave a lighter water, which didn't have the deep flavour I was looking for from a tetsubin, but the water still tasted good.

Also I note the use of Maifan stones & certain stonewares to add minerals to the water for tea brewing.

That's quite a strong statement I quoted above Intuit - have you tried this out to verify it for yourself?

[Intuit]

If water deposited minerals form a crust on the inside of the kettle, the point of having an iron tetsubin with a REDUCED iron layer (as the better Japanese kettles feature), is nullified because the water won't contact the surface, will it?

If your water supply is LOW in dissolved minerals, you may find the addition of *certain minerals* from the stones you mention will enhance the flavor by altering the extraction or by chemical interaction with tea acidic components (mild buffering).

However, certain types of dissolved minerals can and do complex the flavor components of tea and so may affect the ability of the complexed components to bind to taste and odor receptors in the oral cavity.


Per the side note, original post: Previously boiled water that has lost its dissolved gases results in tea tasting flat when the reboiled water is used for making tea.

It's probably better to use freshly drawn water for smaller repeat batch infusions, rather than use a kettle that heats water and then holds it to temp for hours.

Standard caveat: YMMV

[joyfulwoogie]

If water deposited minerals form a crust on the inside of the kettle, the point of having an iron tetsubin with a REDUCED iron layer (as the better Japanese kettles feature), is nullified because the water won't contact the surface, will it?

If your water supply is LOW in dissolved minerals, you may find the addition of *certain minerals* from the stones you mention will enhance the flavor by altering the extraction or by chemical interaction with tea acidic components (mild buffering).

However, certain types of dissolved minerals can and do complex the flavor components of tea and so may affect the ability of the complexed components to bind to taste and odor receptors in the oral cavity.


Per the side note, original post: Previously boiled water that has lost its dissolved gases results in tea tasting flat when the reboiled water is used for making tea.

It's probably better to use freshly drawn water for smaller repeat batch infusions, rather than use a kettle that heats water and then holds it to temp for hours.

Standard caveat: YMMV

I like your reasoning a lot. I sometimes think about how my water will taste when my tetsubin gets a thick white mineral build up. It is not a slight whitening after a year usage.

The water boiled from tetsubin for sure tastes better. This is no placebo effect. I did several blind tasting to make sure and others confirmed in their blind tasting as well. It's just no room for contradicting hypothesis when you own a tetsubin and you taste the difference every time you drink tea from its boiled water.

However, I somewhat agree with you in that the build up of mineral may not add taste to the tea or add unwanted taste. Tetsubin definitely change the taste. Tetsbuin mineral build up, I am not sure. I only have one 30 years or so old iron cast tetsubin.

More than often, though, the experiences of old time tea drinkers beat the highly educated hypotheses of maturing tea drinkers.

[orguz]

The tetsubin I own has been used for 10 months now and the interior has rusty spots dots all over which is fine. The color of the boiled water is clear and not brown, however I only use distilled water and a piece of gypsum as it boils, so far no thick mineral build up and my water is sweet and not flat. I previously placed bamboo charcoal inside the kettle along with the gypsum, but coal particles broke off and ended up in my tea.

Excessive mineral build up interferes with the properties of cast iron imho, at the same time a little does prevent over rusting. Once white vinegar was used to clean my tetsubin this only worsened the rust process, I kept getting cloudy brown water.

Using rice flour and water only if I decide it needs cleaning, and it does the job.

2 cents worth

[Jayaratna]

Using rice flour and water only if I decide it needs cleaning, and it does the job.

This is interesting: which kind of rice flour and how much? Do you mix it with cold water before?


A second question: do you think it's safe to add cold water once you finish the lot you've boiled without waiting for the pot to cool down? I'm afraid of doing this because I fear this could cause the walls and, most of all, the hole at the bottom to split open,


A