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Yixing theory

As a tea noob, I'm starting to ponder the differences between gong fu brewing with a gaiwan and a yixing. Consider with me, if you will:

1. Heat loss: Gaiwans are commonly made with thinner materials which don't hold temperature very well (perhaps most commonly, porcelain). Yixings as a breed are made of clays which do hold their temperatures better (here ignoring that there are those which hold heat better than others). That means that the temperature at which your leaves are steeping is nearer your starting temperature for a longer period of time in a yixing than in a gaiwan. This was "smack in the face" obvious when I did my first infusion with a yixing which I had pre-warmed.

2. Pouring times: I can empty my gaiwan with very little mess in about 5 seconds (as in, it's barely dripping anymore). My first yixing takes 12 seconds or so to completely empty. Consideration number one here is that you adjust your timing accordingly - you start pouring sooner. However, what you then end up with is tea which is slightly stronger later in your pour. If the tea you pour in the beginning infused for about 20 seconds, then the tea you are finished pouring infused for 30! It occurs to me that you're getting flavors from a wider range with a yixing, and thus, the resulting cup of tea is different. Perhaps not as strong as if it were somehow all evacuated at precisely 30 seconds. Perhaps more complex. I don't really know.

3. Material Absorbency: Simply put, the porcelain neither imparts nor absorbs any flavors worth noting. However, yixings are known to absorb and impart flavor. I'm not sure if the nuances of a particular sheng are going to "rub off" on my next tea, or if it's more of the general commonality of shengs at large that lingers in the walls of the pot. But something's going on there, and I imagine it's another flavor-changing component.

Now, I'm not saying I can detect the effects of all of these nuances - I just have a mean engineering streak that forces me to consider them. I can say, however, that it seems as though I'm getting hotter, yet smoother tea from my yixing right now than I ever did with my gaiwan. I wonder if that's because the pot is still absorbing and not yet imparting. I wonder if it will become stronger tea once the clay is quenched.

I wonder if I'm just a little nuts. :blink:
 
Well, I left out another major consideration, which is tea ratio. My gaiwan is 125ml, and I gather this is measured to the rim of the bowl. In typical use, it's actually less than 125ml of water, though. I have yet to actually take measurements, but I'd like to get a beaker to use as a cha hai. In fact, I might be able to pull that off today... we'll see. Let's just say I have access to scientific glassware.

My yixing for sheng is 150ml, and I gather that's measured full to the rim as well. I usually lose a little spillage when I put the lid on. In either case, i get noticeably more tea out of the pot. However, I haven't ramped up my tea amounts, as I'm finding 7-7.5g very enjoyable at this point. I don't run into the "WOW that's strong" cups in the early to middle infusions like I did with my gaiwan. Could be attributed to more water, could be the clay nerfing my tea. I use it 2-3 days per week (I only do gong-fu at work right now, so 5 days a week, and I also drink shu and oolong from different vessels). I think it's still seasoning.

I bought a cheaper yixing for shu. Doesn't seem to seal as well as I get some dribble from the lid while pouring. It's also about 150ml, and I'm noticing fewer differences in how my shu is turning out. I have re-tried some varieties I first drank from the gaiwain, and the results are far more similar.

As to the "longer pour consideration" I'm not noticing that this makes a huge difference in how the tea tastes, to me. Perhaps it balances - you get weaker tea from the top because you pour early, and stronger tea from the bottom because the pour takes longer. Tea is still hotter coming out.

I'd like to get an yixing for oolongs, but I'm afraid one won't do. There's so much variety amongst oolongs that I'd probably want at least two to cover the range of roasting.
 
Dont forget about the shape of pot to the heat retention ratio, the expansion of leaf types to shape of pot , the softness of your water, density and mineral composition of the clay :ohmy:

:laugh: as long as youre enjoying your brew :thumbup1:
 
Dont forget about the shape of pot to the heat retention ratio, the expansion of leaf types to shape of pot , the softness of your water, density and mineral composition of the clay :ohmy:

:laugh: as long as youre enjoying your brew :thumbup1:

I was figurin' it was about time for you to chime in... :lol:

Right you are, Jose.
 
OK, 250mL Pyrex beaker = solid cha hai :thumbup:

I was feeling like shu today, so it was the cheapo yixing we were analyzing for actual output.

Water volume (no tea): 162mL

With 7.5g '06 Menghai V93, after...

60s rinse: 150mL, bang on
First 3 infs: 147mL, +/- a mL

So, to me, it looks like the tea absorbed some moisture and/or expanded to occupy approximately 15cc, or just under 10% of the volume of the vessel. Which is weird, because to look at it, you'd swear it were more. Suppose there's a lot of room in and amongst that pile of leaves at the bottom of my pot.

Now, re-reading some of the logs I've taken from when I used a gaiwan for shu, I was tending toward 7g of tea. I just did a water-only volume measurement with the gaiwan filled to about the point I normally would, and got just over 100mL (bear in mind, this is advertised as a 125mL gaiwan, which I take it is "to the rim" - I can't recommend filling it up that far, as pouring would be precarious). That's a lot less water!

So a big part of the differences I'm seeing is at least somewhat attributable to using less tea/more water, but apparently offset by better maintained brew temperature.
 
Same methods as yesterday, but with my sheng pot, advertised as 150mL.

Water volume (no tea): 162mL (same as cheapo "150mL" yixing)

With 7.5g '07 Xi-Zhi Hao 7542, after:

15s rinse: 145mL
First 3 infs: 130mL

Fairly startling results, as it were - it swelled even more so than the shu did. I think this explains even more why my first experience with sheng (in a 125mL gaiwan, actually only holding about 100mL of water) was so harsh; I still have some of that same tea, and it's a very different animal in the yixing.
 
...
1. Heat loss: Gaiwans are commonly made with thinner materials which don't hold temperature very well (perhaps most commonly, porcelain). Yixings as a breed are made of clays which do hold their temperatures better (here ignoring that there are those which hold heat better than others). That means that the temperature at which your leaves are steeping is nearer your starting temperature for a longer period of time in a yixing than in a gaiwan. This was "smack in the face" obvious when I did my first infusion with a yixing which I had pre-warmed.
...

Going on a little bit of tangent, but when I first read this comment about heat loss I disagreed on the basis that when I pour a cup of hot coffee into different mugs that I have, it seems to be a little hotter when I drink from a porcelain cup versus a stoneware cup. I tried to think of the factors involved, and speculate it could be for a number of reasons unrelated to the insulating properties of the cup's materials. For starters the cups are at room temperature and are not preheated, so the thinner porcelain cup provides a smaller heat sink to cool down the contents, so the coffee is initially hotter. Secondly if the cup is drawing more heat away the contents, then it could be directly transferring more heat from the cup to the mouth when drinking, creating the illusion of a hotter drink. Much like an iced drink seems cooler in a glass versus a Styrofoam cup. And finally my stoneware mugs have a wider mouth, while the porcelain ones tend to be taller and narrow, leaving less surface area on top to cool off as quickly. All helping to provide the experience that the porcelain cup is better.

Anyway none of that matters here, as the teapot is preheated which changes the dynamics. I actually spent some time trying to find a technical answer on the internets, but did not find anything easy to quickly digest. IIRC I did find one report that showed stoneware is slightly a better insulator per unit weight, but the difference was not huge and was hard to pin down as it also depended on what kind of material it really was. Here is one link, but it is doesn't mention stoneware directly: Thermal conductivity of some common materials
 
Three things for consideration, well two and a half really; porosity, mass and volume. Stoneware pots tend to be thicker than porcelain, therefore they displace a greater volume than a porcelain pot that will hold the same quantity of liquid. The greater resultant mass of the teapot creates a sort of heat battery when preheated, in addition earthenware and stoneware are more porous than porcelain acting as a better insulator as well.
 
I can tell you a lot more about how this is working in practice than I can about the theory. My yixing pots are cooler when I first pick them up, but remain hotter once warmed. What causes this, exactly, beyond "the nature of the material", I can't quite articulate. I believe it has a lot to do with material density and porosity, but I haven't done a great deal of extensive study. However, even the cheaper clay seems to do a better job of retaining heat.

That said, soon enough I'll have a new gaiwan to test in this regard - and as far as I can tell, it's thicker (though advertised as having the same volume).
 
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