Do you believe clay-specific heat retention contributes to brew quality?

[teatray]

One often reads that some clay has superior heat retention compared to alternatives. It's said about zisha in general, about duanni/luni compared to other Yixing clay, etc. Such qualities (whether measured or taken for granted) are then used when considering tea pairings: e.g. best to have a "cooler" clay that doesn't cook your greens/oolongs, or a "hotter" one to support your later steeps of aged heicha, etc.

Now, I'm (obviously) convinced that brew temps&times matter and also that clay taste/interaction influence the tea quite a lot. But I'm skeptical about the heat retention part--as far as the material goes; thickness is another matter, probably best discussed in a separate topic. I guess heat retention could mean different things:

1. When filling two otherwise equal tea pots with same temp (e.g. boiling) water, the one made of "hotter" clay will have a less steep downward temp curve and contain measurably hotter water before both reach room temp.
2. When you fill and drain two otherwise equal pots using boiling water, the "hotter" clay will keep more heat for longer and make a subsequent steep start hotter.
3. both of the above

Would it be wrong to say that (1) is mainly a question of thermal conductivity, while (2) is mainly about specific heat capacity (though both play a role in each case)?

I'm skeptical that differences in specific heat capacities matter much, because the possible range is probably quite narrow, and is in any case dwarfed by the specific heat capacity of water (which is also >50% of the mass of the full pot). Thermal conductivity may be a factor, esp. for flatter pot shapes that touch a lot of solid surface, but is also easily compensated by a small amount of added water due to its high specific heat capacity (increasing overall starting heat).

This would mean that, if you believe some tea would really benefit from the hottest possible treatment, and your choice of pots is an 80ml and a 90ml (of the same shape & wall thickness), you should definitely prefer the 90ml, regardless of what clay the two are made of (even if the 90ml is made of the "coolest" and the 80ml is made of the "hottest"). Conversely, if you feel like starting with boiling water but are afraid of "overcooking", your best bet is to use the smaller pot (apart from other interventions like opening the lid). Clay-specific "heat retention" would only come into play when using the same volume, as a very minor factor (best ignored in favor of larger volume).

If you disagree, I'd be interested in what you believe to be the main meaning of heat retention--(1), (2), or something else--and whether you feel like confirming your perceptions with thermometer & scale.

Vid: Comparing a 120ml luni (72g w/o lid) to a 140ml zhuni (81g w/o lid). When filled, the zhuni beats the luni handily, as expected, ~2C hotter after 5 mins.

[buullon]

Your experiment is neglecting a few things.

1. More water take longer to cooldown
2. Shape and volume of clay to heat
3. The temperature of the water after being filled (some of the heat was absorb by the clay to reach maximum temperature)

[teatray]

Your experiment is neglecting a few things.

1. More water take longer to cooldown
2. Shape and volume of clay to heat
3. The temperature of the water after being filled (some of the heat was absorb by the clay to reach maximum temperature)

I agree that my experiment is not to be taken seriously. I lack the pots to gather the best data to compare, so this was just a quick demo, not intended to serve as basis for the considerations I wrote about.

(1) is what it was intended to (very roughly) show, my overall hypothesis being that water volume far outweighs any temp-related clay considerations, maybe to the point of complete irrelevance vis-a-vis other factors such as clay taste
(3) is actually in favor of the luni ("hotter" clay) pot: its water to clay ratio (by weight) is higher, so there was less clay to heat per unit of water (yet it still got colder faster)
(2) but yeah, pot shape is completely unaccounted for

[Baiyun]

Since we rarely choose from a lineup of identical pots with the luxury to nitpick only one or two variables, I would generally think about pot-specific, rather than clay-specific, heat retention and its effect on tea.

I personally take volume out of the equation to begin with, despite its important effect on heat retention, because I base this solely on the amount of tea I would like to make per infusion. I am not going to buy a 150ml+ pot just because it stays that much hotter for longer if it makes too much tea.

The shape may also have more to do with what leaves easily go intact into the opening and can fully unfurl and be retained nicely within at a given volume, when it comes to pairing. I am not going to mismatch this for the sake of heat either.

Which leaves us with clay and wall thickness, and here I am more inclined to align clay with the type of tea and the notes I wish to retain (more of a focus for me) or subdue (never been a real focus for me), and wall thickness with heat control, because I think this is how these factors most noticeably interact.

So effectively, wall thickness is the only remaining thermal property influencing factor, the way I think about it, once everything else has been more closely associated with other aspects of the brewing process, so I think that clay-specific heat retention is too easily overridden to significantly affect brew quality.

Even thick or thin walls can be worked with based on whether and by how much they are preheated, meaning that while there are more or less ideal combinations, if all else works out nicely, it does not mean that a pot is unsuitable just based on wall thickness.

Still, I find this highly theoretical and would be surprised if things work out as intended when shopping based on such considerations. I think in the future I am just going to buy pots that I think bring an interesting new dimension to my brewing and then see how this plays out by trying all sorts of things.

[Bok]

I think in the future I am just going to buy pots that I think bring an interesting new dimension to my brewing and then see how this plays out by trying all sorts of things.

That’s the gist of it. Unless one has already amassed dozens of different pots it’s next to impossible to judge a pots performance based on specs only.

[LeoFox]

I think in the future I am just going to buy pots that I think bring an interesting new dimension to my brewing and then see how this plays out by trying all sorts of things.

That’s the gist of it. Unless one has already amassed dozens of different pots it’s next to impossible to judge a pots performance based on specs only.

100%

[teatray]

@Baiyun good points, but regarding volume, I believe even a choice within a narrow "preferred drink range", for example between a 90ml and a 100ml pot, completely overrides clay-specific temp considerations (leaving aside clay taste, shape, wall width and other considerations that may be deemed more important anyway). I think the arguments presented necessarily lead to that conclusion, but I may be mistaken, and don't have the pots to experimentally check anything. I imagine many collectors have very similar pots (~same capacity, weight, shape, just diff clay) and it may be interesting to hear from them, esp. if they hold the opposite view & would like to share measurements.