Tetsubin Seasoning

[S_B]

Posting this one up because I am either one of the dumbest tetsubin owners there is, or perhaps this isn't common knowledge out there for Western users and I think either way it is important to share depending on the water they use, where they live, and how they use their tetsubin.

I decided to do some upkeep on my tetsubin today. It has a fair amount of rust (as shown on pictures below) but nothing that ever concerned me, since water comes out tasting just fine, and comes out nice and clear.
Most of the time I am pretty lazy, and just use filtered tap water when making tea with the tetsubin. Where I live, water is pretty soft, going near 50 tds give or take in slow-usage months, and somewhere around 120ish in higher use months with some well-water blended into our surface water.

I have always been a "disciplined" user of my tetsubin. I never let it sit with water (minus one occasion when rushing out the door), and make sure to dump out water whenever I finish my tea session, making sure the tetsubin is still hot so that it can fully dry. What I didn't realize is that my caution MAY have caused my rust problem. Through my tetsubin use, I would generally bring it to boil, then pull it off the stovetop and use it for a few steeps before refilling back to "full" and carrying on. Rinse and repeat that process.

Fast forward 4 years later and we are here:

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So...I went about brushing off the surface rust, as it was nowhere near a threatening level, and proceeded to boil some tea, allowing it to sit for 2 or so hours. I repeated the boiling process twice, and after all was said and done, rinsed out and ready to go, my inside looked like this:

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For those who may have somehow missed the message, or may have similar water or silly habits like mine, I want to add this post as an additional advice post for those picking up tetsubin and looking to keep them nice and cared for. Season your tetsubin with minerals! Through normal use, keeping your tetsubin water boiling and not refilling until maybe...1/3 or 1/4 full, and allowing for water to evaporate, you should naturally reach a nice initial mineral crust within your first few weeks of use. For those looking to accelerate that process for whatever reason, dedicate a few hours of your day to doing the following simple step: Boiling water. Since my water is pretty soft for most of the year, I don't think I was using my testubin in such a way that allowed for enough evaporation to occur, thus never creating an adequate mineral barrier inside my kettle. My hypothesis is that it was my day to day use - constantly refilling the tetsubin because I didn't want to let it get too low inside (for thermal mass or whatever silly reason) and seldom letting it simmer on the stovetop between steeps, and never reboiling without adding fresh water that probably caused my circumstances despite 4 years of constant use.

Today I took some spring water (I used Crystal Gyser Olancha since it is what I had on hand) and boiled it down over the course of maybe 3 or 4 hours. As the water evaporated to about 1/4 of the tetsubin full, I would just add more water in and wait 45 minutes or so to keep adding more water. 1.5L of water later, and I had this:

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You'll know you've started an initial coating of minerals once you get this interesting sparkly rainbow effect inside your kettle. Pictures never quite show it all...what I see in person are blues, and purples, and violets, with both solid white spots and sparkly spots all over. While it may not look as frosty as you might expect, there is already a coat of mineral formed on the inside, keeping your tetsubin nice and safe from too much water exposure. While I used spring water to start with a higher tds to speed things up, even with soft tap water like mine (or possibly yours) this process is completely possible to do no matter your water source. So long as you are reducing the water through evaporation, those minerals will eventually bond.

I only have one other anecdotal data point to report, however, I think it is still useful to discuss. I have a fellow tetsubin-using friend that I discussed my tetsubin situation with this morning before geting to work on this project that shared some interesting info with me. Their tetsubin has been used for a similar number of years as mine and has not seen but a few tiny places of minor rust. This friend even leaves water in their tetsubin overnight somewhat often (never intentionally but more frequently than might be expected), with no rust forming at all due to the protective crust layer their tetsubin has naturally formed over the years that mine so sorely lacked. Obviously, I'd say in general not to recommend doing so just for fun, but if your tetsubin is seasoned up correctly, this shouldn't be an issue.

I hope this helps one or two other folk out there that may be in the same situation as myself, and may not have yet sought out solutions to their problem. My dedication to treating my tetsubin "well" was misplaced....hopefully others can avoid my mistake! Cheers

[.m.]

Thanks for sharing!
The way I see it it's always a struggle to keep rusting under control, it's just part of it.
My question: Would a layer of scale protect the testubin from rusting to some degree or would it rust as much underneath hidden from sight?
I hypothesize that the composition of water could play significant role in how quickly the rust forms, the pH, amount of oxygen or other gases dissolved, amount of iron dissolved, etc.

[S_B]

Thanks for sharing!
The way I see it it's always a struggle to keep rusting under control, it's just part of it.
My question: Would a layer of scale protect the testubin from rusting to some degree or would it rust as much underneath hidden from sight?
I hypothesize that the composition of water could play significant role in how quickly the rust forms, the pH, amount of oxygen or other gases dissolved, amount of iron dissolved, etc.

Interesting...that probably does factor in, too!

I guess my next question would be - once your tetsubin has a coating on it, should it keep rusting, how do you go about cleaning the rust that is underneath the mineral layers?

[Balthazar]

Would a layer of scale protect the testubin from rusting to some degree or would it rust as much underneath hidden from sight?

Schrödinger's tetsubin!

[S_B]

Would a layer of scale protect the testubin from rusting to some degree or would it rust as much underneath hidden from sight?

Schrödinger's tetsubin!

Though I suppose if this were the case and it could still rust, then treatment would still reach the rust the same, no?

If water is contacting it to cause rust...so too would tea water or whatnot used to stop it