When an oolong has been over-roasted, time and patience are necessary for it to have a chance to recover. Weeks or years may pass before the fire subsides and one can taste the tea base again, but all too often, the fire remains long after the roast. Some of the aged oolongs that one may come across were once over-roasted teas that have been set aside to rest and recover over the years; they’re sometimes forgotten about. Some of these teas have been roasted to death and the tea will never recover.
Those searching for a pleasant aged oolong should recognize the difference between an aged tea with potential and one that has been roasted to death. Irrecoverable over-roasted teas are especially shiny, have a particular taste that can seem nutty/smoky/caramel-like, and fail to open when brewed. There are several retail and online shops that pass such tea off as premium, aged tea (with the lofty prices to match), but don’t fall for it!
A simple way to understand the differences is through some experimenting. Ten to 20 grams of a hardy, well-oxidized oolong like a traditional TGY or Wuyi oolong would work nicely. If you have a mini-roaster, set it to 90+ degrees and intentionally over-roast the tea over several hours until it smells like it may be burnt. If using an oven, set it to over 200 degrees. Loosely wrap the tea in foil and leave it in the oven for at least several hours. This is not enough roasting to kill the tea, but it will be enough for you to taste significant changes to the tea. You can try it shortly after and note how different the base of the tea is from the pre-roasted version. Better yet, wait several days or several weeks for the roast to subside and taste the tea again to see what’s changed.
As usual, buy small quantities to sample before making a bigger purchase. You may end up with little baggies of junk this way, but that’s way better than big bags of crap!