I'm a fan of modernist cooking, and its emphasis on precise measurements and consistency. I'm curious how to apply this to tea preparation - in particular, several things:   It seems to be well established that different types of tea should be prepared at different temperatures - black tea and fruit infusions with boiling water, green tea at 80 degrees centigrade, and so forth. Where/when was this established? How do we know it's optimal for each tea? Likewise, durations to steep tea seem fairly well established. Is there any research on this? People seem a bit fuzzier on this than on temperatures, with some variation. There's a lot of variance on the amount of tea leaves per litre of tea, varying between 2 grams per cup (8 grams per litre) and 15 grams per litre! Obviously, this depends on how finely cut the tea is, too. Is there any way I can determine this more objectively than just trying different amounts and tasting? There seem to be several theories on how best to prepare iced tea. Some suggest using more tea and steeping for longer, some suggest preparing it cold, and so forth. Has anyone determined objectively which are better?   I realize this my come across as rather pedantic, but given the huge variation in preparation suggestions, I'm interested in trying to figure out which work best. Most of the questions above could be answered to some degree, too, with an explanation of what it is - chemically - that makes one batch of tea better or worse, providing a foundation for making these sort of decisions. 
There is an ISO standard for tea preparation.  To quote the summary:        The pot should be white porcelain or glazed earthenware and have a partly serrated edge. It should have a lid that fits loosely inside the pot.   If a large pot is used, it should hold a maximum of 310 ml (±8 ml) and must weigh 200 g (±10 g).   If a small pot is used, it should hold a maximum of 150 ml (±4 ml) and must weigh 118 g (±10 g).   2 grams of tea (measured to ±2% accuracy) per 100 ml boiling water is placed into the pot.   Freshly boiling water is poured into the pot to within 4-6 mm of the brim. Allow 20 seconds for water to cool.   The water should be similar to the drinking water where the tea will be consumed   Brewing time is six minutes.   The brewed tea is then poured into a white porcelain or glazed earthenware bowl.   If a large bowl is used, it must have a capacity of 380 ml and weigh 200 g (±20 g)   If a small bowl is used, it must have a capacity of 200 ml and weigh 105 g (±20 g)   If the test involves milk, then it can be added before or after pouring the infused tea.   Milk added after the pouring of tea is best tasted when the liquid is between 65 - 80 °C.   5 ml of milk for the large bowl, or 2.5 ml for the small bowl, is used.     