I'm trying to figure out, in very general terms, what the variables in tea production are (e.g., not varieties of tea leaf or tea growing regions, and not brewing variables). For now, I am leaving Pu-er out of the picture, because that seems to add a seperate layer of complexity. From various sources, and especially Hou De's video on the manufacture of Formosa Oolong (easily found on You Tube), I have narrowed things down as follows:
- Tea is picked -- this can be mechanical, or hand-done, and can be done at several different times of year, or in different conditions, or at different stages of tea leaf growth. This variable is huge and there are a lot of parts to it.
- Withering -- to me, this looks like some sort of abbreviated drying process, where leaves are given lots of air and frequently "stirred". It can be done indoors or outdoors, but no heat other than sun is added. Tea still has significant moisture afterwards and the leaves remain very pliable. I really don't understand what this step does. It seems like this is almost a sub-step of the next variable.
- Fermentation -- I'm not sure I fully understand how this differs from withering, though it may be that the leaves are left in a pile and stirred less frequently (or not at all?). This does not appear to involve any particular heat sources. I would guess this step would be skipped in green or white tea production, because my understanding is that this step is what seperates oolongs and red/black tea from the green and white tea. Afterwards, I imagine the leaves still have a lot of moisture and are still very pliable. Degree of fermentation is a huge variable, but there are no other real additives in this step so this is a pretty easy variable to identify.
- "Kill-green" -- this can involve pan-frying or oven roasting (steaming seems unlikely given the overall goal of reducing moisture) but seems to be the first time that a heat source other than the sun is added to the mix. I would guess that the tea would have to reach a certain temperature to stop the fermentation process. From the Hou De video, it is apparent that the leaves can remain flexible after this process, though I've seen some other video on long jing production that seems to show a finished product after the kill-green step (maybe because this step combines the next steps into one for this particular tea?)
- Shaping/Further Drying -- after the kill green, the tea may still have moisture in it and the leaves may still be pliable. So I guess this is when leaves are twisted or rolled, and I imagine that shaping process is interspersed with various drying efforts that use some sort of heat sources. The variables here that may affect flavor or aging potential would be shape and perhaps the drying source (e.g., charcoal, electric heat?). I would guess the goal of all tea production is to reduce moisture levels to similar levels, no matter the tea, so extent of drying is probably not a variable here. Maybe speed of drying process and temperature are variables.
- Roasting? -- the Hou De video doesn't appear to show tea roasting, but tea roasting is clearly a factor in some tea production. I'm not sure what that process would do other than further reduce moisture and perhaps change the flavor somehow (I imagine you are basically cooking the tea, which would change the flavor of anything). The variables here would be similar to the drying variables above -- charcoal or electric heat, as well as temperature and time. Maybe the drying is a type of roasting.
I hope this doesn't repeat too much anything that has previously been posted. Seems like I never see this information in one place. If anyone has comments on the above steps in the form of additions/ subtractions/clarifications, I would be appreciative.
-Charles