Akadama types of fired clays

Wich is the differences between akadama Jirushi, Kobayashi, Ibaraki, tripple line, Tokoname… Please anyone can to explain in details the characteristics of all these types of fired clay… Temperature, hardness, etc


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Well what I can tell you is I have purchased Ibaraki and it seems to be of good quality, not crumbly or dusty, and survived the winter better than a cheaper product I tried.

Yes, I support this, I’ve been trying to gather more information on different kinds of Akadama and firing temps. Here in Guatemala where I live I have been buying some “Akadama” from a Bonsai store, it is mined here, we have also a super volcanic terrain and many many volcanoes around the country. That being said it has been really hard to get information out of the Bonsai store owners (People here are super jealous about knowledge and sharing information), and I don’t really know much about it just yet, I plan on getting it analysed as soon as I have a chance but it looks very similar to the japanese stuff, albeit a bit harder. I have two groups of trees that were just repoted, some into the “guatemalan Akadama” and some into japanese Akadama, will post information as soon as I see the progress, and I’ll also post some photos tomorrow once the light is back.


I tried finding more information on Akadama a decade ago. I found references to it in a rather dry book called “Clays and Clay Mineral of Japan”. Technically Akadama is Imaichi pumice, the leftovers of a pyroclastic event a long time ago.

I will take the example of the Kanuma quarries as they are the most documented in scientific literature.

The uppermost part of the pyroclastics in this area, the Shichihonzakura Pumice and the Imaichi Pumice, which both derive from the Nantai volcano, is distributed only in the northern part of the area.
A volcanic ash bed underlies the Imaichi Pumice, and then comes the Kanuma Pumice. Both beds are distributed throughout this area. The volcanic ash overlying the Kanuma Pumice is composed of Clays and halloysite associated with allophane and vermiculite, when it is covered by the Shichihonzakura and Imaichi Pumices.
On the other hand, it is composed of allophane associated with imogolite, gibbsite, and vermiculite-chlorite intergrades, when it has no overburden.

There are usually 4 strata in the Kanuma quarries. The top-most strata is black soil that will either be put back in place or sold for gardening (depending on the company). The second strata is Shichihonzakura pumice, a yellow pumice. There is a layer of ashes then a strata of Imaichi pumice, a red/orange pumice. There is another layer of ashes before reaching the Kanuma pumice, which is light yellow to white depending on the local conditions and the depth.

The two strata that interest us are of course the Imaichi and Kanuma stratas. Some producers (Heiwa is one) do dry those pumices in a 300C kiln, as they are more likely to crumble when humid. Drying them reduces losses in the packaging and transport activities.

This is probably what gets confused as “fired” but if Akadama was really fired it would lose all its interesting properties (CEC being one).


Akadama isn’t fired. I personally like Double Red Line (not sure if that’s the brand, but that’s what’s on the bag). Not much dust and doesn’t crumble too much…hence not much dust.


Thank you for this, I find it incredibly hard to believe though that this is the only place in the world where this kind of “pyroclastic event” has happened. I’m really putting a lot of hope on this “Guatemalan Akadama” It looks and feels exactly like Akadama, maybe it has not been dried in any kiln or anything… no idea so far… Really wanting to dig into it but it’s really hard with the people selling it here atm, they don’t like to share much… lol… understandably… if it has the right properties they are sitting on a gold mine.

That being said, does anybody know a place where they would analyse this stuff properly to know how similar or if completely different it is to japanese akadama?

There were indeed pyroclastic events all around. That’s where pumice, zeolite, chabazite, basically most of the mineral components for bonsai soil come from. It is my understanding that a lot of the differences come from both the rock composition in the area and the rate of cooling down after the event.

I’m with you on the “they don’t like to share much”… there was a lot of the same with the Chabasai guys in France. I’m 99% confident it’s just chabazite-ca, which is available in a lot of quarries around the world (including 2 in Costa Rica) but they like to claim that their product is the only chabazite that is usable for bonsai. Of course, they also keep the exact quarry under wraps to avoid people bypassing them.

The geology department of your closest uni may be able to help with the analysis if you bring samples of both :slight_smile:

Yeah, I was planing on bringing it to the geology department of the national University, accordingly to the guys selling it this university has already made studies in their behalf and of course its even more “nutritional” as they put it than akadama. Of course this might actually mean that the CEC is better. I’ll be bringing some samples as soon as I get my hands on really good quality akadama.

Makes sense that it would be exactly the same situation as with Chabasai. I’ll be in europe next month and I’ll try to procure some Chabasai as well.

Getting Chabasai may be problematic because almost no shops carry it right now… it may be related to the high amount of people disappointed with it after 3 years of use or it may be that the distributor prefers selling it abroad for an even higher price.

From repeated posts on French forums, it seems that the pH of chabasai is too basic which leads to nutrient assimilation issues so the plant grows like normal in the first year, starts stalling in the second year then declines in the 3rd year. A high CEC is only one part of the equation :slight_smile:

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Oh, this is interesting. so that means that the actual pH of akadama is imporant, what’s the average pH on japanese akadama? Do you know the geological term for the “pyroclastic event” they refer to in all this literature you read?

And do you really think that the pH is the variable making the difference or the fact that this minerals e.j. Chabazie do not decompose in the same manner as akadama? creating the complexity in the root system that ensures growth perpetuation…

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Well to put it simply… plants tolerate a pH between 6 and 7.5 as it’s the sweet band where most nutrients are available to them.

In highly acidic soil, aluminum and manganese can become more available and more toxic to plant while calcium, phosphorus and magnesium are less available to the plant. In highly alkaline soil, phosphorus and most micro-nutrients become less available. Calcium is required for cell walls and is only readily available to the plant if the pH is between 6.5 and 7.5… there’s some availability between 6 and 6.5 and between 7.5 and 8, there’s close to no calcium available below 6 and above 8. Iron is only readily available below 6, and becomes unavailable from 8… it is required for chlorophyll production (along with magnesium and nitrogen).

In the case of chabasite, the consensus on the French forums seems to be that the difference is in the pH… the price also didn’t help as it is/was very expensive.

I have personally tested all kinds of alternatives to akadama and they all worked to some extent… small size lava, baked clay (Seramis), baked clay (MaxIT Clay AS), crushed granite, crushed basalt, pumice, sepiolite and various mixes of those.

The only one I wouldn’t recommend is sepiolite as it tends to clump back once roots have grown between the particles… but the growth I had in it was impressive. I had to use a hammer to free the cuttings that were growing in it.

I’ve used Seramis for ages, long before doing bonsai and it’s a great soil component with an ugly color (bright brick orange). As it doesn’t break down, it can be washed and reused.

MaxIT Clay is dirt cheap and you probably have local equivalents… it’s a small particle size baked clay used for insulation and as concrete ballast. It doesn’t break down at all so you can leave plants in it as long as you want/need, you can also wash it and reuse it. I’ve grown Picea abies seedlings in it, they’ve been in it for 10 years and gave me tiny needles without any work on my side. I’ve also grown a super-dwarf Japanese maple (Acer palmatum ‘chiyo-hime’) in it and got very reduced leaf size without any work. I did test pinching the buds one year and the result was leaves smaller than my pinkie nail with internodes so short that the buds were touching.

Crushed basalt has close to no water retention… which is nice for the winters around here but you need to water several times a day in the summer. I had great growth with junipers using this one.

Lava works nicely for conifers but may not offer enough retention for deciduous if used pure.

All those absolutely require using an organic fertilizer that leaves humus behind or a mineral fertilizer (or adding some peat or composted bark).

I’m currently using an akadama/lava/pumice mix.