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I have been acquiring these kyusu since production began and thus have 2 generations of each. Victoria suggested a topic directly comparing the tea brewed using these kyusu. I will be starting it off and will add future comparisons with other sencha in the very near future.

If you have been on this forum for any length of time, you likely already know that these are proprietary clays produced under direct supervision of Akira Hojo who is among the most fanatical students of Japanese clay for brewing tea ... not just Japanese. However, my personal comparisons will be limited to Japanese sencha.

For each clay, I have 1st generation kyusu. For the Junzo Kobiwako I also have the most recent generation. For Tachi Shigaraki I also have a later generation.

For this round I brewed the same sencha in all 4 kyusu.

The primary focus of this topic, how do these clays (seemingly) affect the flavor profile of tea. Although, I anticipate rabbit trails.

"Shall we begin?!?"

Yes! Let the fun begin!

Paying attention...

I begin this test with a new bag of Sae Midori fukamushi from O-Cha.com. I purposely chose this selection for this comparison. Sae Midori is typically a milder clone. Subsequent selections will be quite different from this selection.

Should be a fun ride!

Again, the primary focus of this comparison test is on taste alone

All 4 kyusu were used in this first round. Going from first generation to a later generation did not produce any discernable or significant changes. So I can keep this less confusing by focusing on 2 kyusu, one for each clay/potter.

For each clay, I used 10 grams of leaf per about 7 ounces, 210 ml water.

First up, 1st generation Kobiwako kyusu by Junzo.
As has been my experience with this clay, it predictably produced a sweet liquor devoid of bitterness and astringency. Umami was assertive and very pleasing.

It was flavorful yet exhibited some mildness that is to be expected from this clone. Yet it was more flavorful than most clays ... virtually all clays I have used over the years. It was outstanding!

This clay combined with this sencha ... it is almost too easy to produce steep after steep, session after session of great sencha.

There is a joining of clay and leaf ... they are simply natural together. I sense that I could really amp up the leaf.

The aroma coming from the kyusu after the first pour literally made me smile, so appealing and pleasing.

I rate it a perfect 10 for this sencha selection.

Next up, 1st generation Tachi Shigaraki.

Please forgive me for saying first off, for some reason either consciously or subconsciously despite owning this kyusu for around 12 years, I have only reached for it maybe 6 times ... despite the fact that it is gorgeous and so skillfully crafted.

Still, i just never felt a symbiosis of clay and leaf.
Again 10 grams per around 7 ounces, 210 ml.

Clearly for this taster, this clay seems to AMP UP ... EVERYTHING! ASSERTIVE, BOLD are adjectives that come to mind.

There is generous sweetness and umami present, but surprisingly there is bitterness and astringency also competing for my attention. Sae Midori is not known for bitterness nor astringency ... quite the contrary. Its assertive presence is directly competing with the sweetness and umami.

... and there is ... is it ... could it be ... a hint of iron. Yes. Ok, Iron is in this clay, but I am not used to tasting iron in my sencha.

Overall, this is a crazy menagerie of competing, somewhat disharmonious ... flavors. It is a bit ... bizarre to me. It is definitely assertive!

The aroma is not as ... pleasant as the Kobiwako. There is a hint of iron even in the aroma.

Anyone who is sensitive to bitterness would likely have an issue.

Yet, this is unique and interesting. No other clay I have tried is so reactive. But symbiosis between the clay and leaf? Not sure that is what is going on here.

I don't sense that I could really up the leaf like I sense with the Kobiwako.

I find myself asking, do I like this? I find myself answering yes AND no. I am left teatering ... er teetering on the fence.

Still, I'll give it a 7 out of 10.

One other observation.

Kobiwako brewed perfectly right out of the box.

Tachi Shigaraki ... maybe a break in seasoning would tame this beast.

Boil the teapot in clean water for 2-3 hours, change the water, repeat 3-4 rounds or more.

When I first got it a few years ago, it made very bold tea like you said. It was like using double or tripple amount of leaves. At one point there was also strong cheese smell, probably mozzarella. Ha ha ha

After the heavy boiling my pot has made nice and clean sencha.

Chip wrote: ↑

Mon Sep 30, 2019 12:13 am

One other observation.

Kobiwako brewed perfectly right out of the box.

Tachi Shigaraki ... maybe a break in seasoning would tame this beast.

Chip, thanks for doing these comparisons. Will be interesting to see how other results present themselves. Since you have owned these pieces for some time you’ve most likely developed opinions about them individually. Did you try a side by side blind comparison between clays?
Also, looking at your picture of Tachi’s Shigaraki kyusu, the clay looks less textured than the one I have, is this just the photo, or are older ones using more refined clay?

For the comparison between Shigaraki and Kobiwako clay kyusu I chose as a benchmark a sencha I’d been having all summer, an award winning 2018 Kabusecha Sae Midori from Kagoshima Seicha (Organic Sencha 2018, Smile Tea by Birouen Tea House). I did side by side comparisons, so I could taste any differences back and forth, during each steep. To double check results, I did two separate side by side sessions with each kyusu; one filling each to capacity, the next session using the same amount of leaf and water with each kyusu. Unfortunately, my kyusu are not equal in size, so I adjusted to accommodate this difference proportionally in the first round. Both of my kyusu are pretty new additions; the Tachi Shigaraki kyusu April 2019 (used by previous owner), and the Junzo Kobiwako kyusu early September 2019 (unused). I have used Tachi’s Shigaraki at least once per week since getting it, and Junzo’s Kobiwako pretty much non-stop since getting it.

The Shigaraki clay kyusu produced better results overall, with richer umami profile and no bitterness, whereas the Kobiwako clay kyusu brought out bitterness and higher citrus notes I had not tasted using Shigaraki or Yamada family Shudei clays. I was actually surprised by the results, having enjoyed using the Junzo Kobiwako clay kyusu in earlier sessions with this same sencha. I think doing a side by side comparison really brought out the differences between the two. Differences in size and form between kyusu probably had some effect on results also. I will conduct the same test between clays using Lishan next time.

1st side by side session - filling kyusu
5g/100ml/155f/1.30 in Shigaraki clay Masaki Tachi 120m, filtered tap. Aromatics on heated dry leaf richer, may be because of shape of kyusu to smaller opening size. Perfect fast pour, no dripping. Tastes smoother, better.
10g/200ml/155f/1.30 in Kobiwako Clay Maekawa Junzo 240ml, filtered tap. More bitter. Strange because I had not noticed any bitter notes prior to this comparison. Thinking bitterness is a function of relative conditions. So since Shigaraki clay results are smoother Kobiwako bitterness coming through is relative / comparative.

2nd side by side session - using equal leaf and water
5g/100ml/155f/1.30 in Shigaraki clay Masaki Tachi 120ml, filtered tap. Smooth! Umami rich silky. Warming sits in cup comfortably. 2nd steep thinner, but tastier than Kobiwako clay.
5g/100ml/155f/1.30 in Kobiwako Clay Maekawa Junzo 240ml, filtered tap. Rich tasty -higher notes accentuated. Almost more citrusy notes, less umami. Some warming umami notes are reduced, doesn’t sit as cozy in cup. 2nd steep thinner, flavor profile reduced.

@Victoria I think it might have to do with the size difference. Although you adjusted to compensate, the larger Kobiwako will produce more sustained heat than the Shigaraki, so the bitterness as a result?

What about wall thickness? Are the two equal? I was also under the impression that the Shigaraki is less dense than Kobiwako, which will probably result in faster heat loss?

@Chip and @Victoria, would be interesting to compare the mineral contents of the waters being used, in case that could account for the different experiences...

Yes, size difference will make a difference even though I compensated for this in my second side by side using equal leaf and water. The wall thickness between kyusu is pretty similar. My filtered city tab water was working fine with other teas the day before, that day, and a few days after also. Brita filtered has180 TDS (unfiltered 260TDS, 8.2 pH, 109 Alkalinity, 154 Hardness, 37 Calcium, 16 Magnesium). I’ll use Icelandic Spring bottled water next time, 53 TDS.

@Chip what water did you use?

@Victoria Yet equal leaf and water ratio does not compensate for heat retention. For that the larger would probably need slightly shorter infusion times.

Water Test: Glass, Shigaraki & Kobiwako clay


Using filtered tap water, in the glass I could taste a slight amount of very fine particles in the water, slightly less so in both Shigaraki kyusu, but less so again in Kobiwako clay. In Kobiwako clay the water was smoother, texture is silkier, as if particles are filtered out. Shigaraki by Tachi Masaki water was more filtered than that in Tani Seiuemon shiboridashi. It is interesting though to compare how they brew tea differently.

Left to Right: Ton Haas wobble glass, Tachi Masaki shigaraki clay, Tani Seiuemon shigaraki clay, Maekawa Junzo kobiwako clay

Would be nice to have a kettle made of Kobiwako clay.

p.s. this comparison was done last week, before kabusecha test above. Comparison Kabusecha with Shigaraki Tachi Masaki vs Kobiwako Maekawa Junzo clays .

Aw, dangit... I may have to buy another pot from HOJO

@tjkdubya It is interesting that you bring up water in this post and in the Hokujo/Kobiwako/Iga post. I finally got around to looking at the mineral content of the water I use. The TDS is 149 mg/L, PH is 7.74, magnesium 1.6mg/L, potassium 0mg/L, calcium 51.4mg/L. I wonder if that high calcium is greatly affecting my results.

I've only used this water, so I have nothing to compare it against with tea (anyone got any lower calcium brand suggestions I can pickup at a store?), but I used to roast my own coffee and switched to this water after it was very apparent that using the unfiltered tap water in my city yielded much poorer results when brewing it.