|This teapot has a cute nickname, "little dumb"|
Here are some methods that I could think of at this moment, including some methods that I'm reluctant to use but being used by a lot of experienced yixing collectors.
All the methods mentioned here are for legitimate yixing teapots. They are not useful to detect any harmful chemicals in the teapot or "cure" the teapot from any permanent harmful contents. Some of the methods may help to reveal the clay quality to some degree, but this is not a practical aim of preparing teapots. Whatever flaw that could be reflected in these method, could be detected in other observations before hand.
As usual, I know I will be too wordy to control the reasonable length of the post. So I would divide the contents in 2 posts. Part one is about the routine and popular methods. And part two discusses some more controversial method and some "queer" methods.
1. To judge if a yixing teapot is ready to use.
To judge whether a newly obtained yixing teapot is ready to be used for tea brewing, other people may have more decent ways, but to me, there is a very important test, which doesn't sound very decent ;-) This very important test to me is... Sniff Test! Basically I would sniff a teapot around to decide whether it's ready to be used for tea brewing or it would need more "preparing" work.
The purpose of the sniff test is to see if there are dust residues hidden in the pores of the clay texture. This is not a test for any additive harmful chemicals, though, because many harmful chemicals are odorless.
The key to the sniff test is to sniff the teapot when it's moist but not holding water or having a lot of water on the clay surface. When the clay is moist, the dust odor is most prominent, if there is any. But when the teapot holds water, a lot of the odor is dissolved by water and can't be detected as easily. For a new pot, it's almost ready if it still has some hint of pleasant, aromatic odor of clay (shouldn't be strong though). It wouldn't be good if the odor is heavily soil-ish (need more rinsing, or the the teapot didn't have enough firing in the kiln).
2. Simple rinses may work sometimes.
In the most ideal situation, "preparing" work is minimum to none. For some high quality, high fire modern teapots of certain clay textures, the only thing needed in preparation work is to rinse it for a few rounds with tap water and then with boiling water. It takes 1 minute and the teapot is ready. Some vintage teapots could be ready with some simple rinse too, but considering the time the teapot might have spent in a dusted warehouse or an unknown place, probably more preparation work is necessary.
If the user would like to have some fun to go through more tedious preparing work, as described in this blog post, it is fine. But it's not always necessary.
In my experience, a lot of zhu ni teapots, ben shan green clay teapots and red clay teapots would get ready with such simple rinses. High-fired purple clay and duan ni teapots with relatively smooth surface may belong to this category as well. Usually, after simple rinses, if I don't see tiny piles of clay dusts inside the teapot, and if the teapot passes sniff test, then I would start using it if I'm very eager to start using it.
3. Rinsing with boiling water.
For most of my new teapots, I would rinse them with boiling water for many times. I don't spend extra time rinsing a new pot, but just rinse it when drinking tea. The teapot is filled with boiling water, and then rinsed some time later, and filled with boiling water again, and rinsed again. This could last for a few dozen rounds and a few weeks. I would give the teapot a "sniff test" from time to time, to judge how ready it is. But usually the rinsing time is more than the teapot needs to get cleaned. The rinsing helps to season the teapot anyway, although it's just plain water. So I wouldn't mind over do it.
I like this method much better than boiling a teapot in a pot of water, which is also a popular method of preparing the teapot. This method takes longer time, but it's fun anyway, and for many of you who've already got more than enough teapots (admit it!), you are not in a hurry to get a new teapot ready anyway.
Some new teapots has small piles of clay inside the pot, semi powder and semi clay, but removable. Many high end teapot makers would be careful enough not to leave such small piles, or remove them in the quality control step - that's partially why teapots from high end makers are often very easy to prepare and method #2 would be enough. But having left over clay powder in the teapot doesn't necessarily mean the teapot is low quality. Sometimes a relatively careless potter is even more skillful than a relatively careful potter. For teapots with left over clay, I think multiple rinsing would work much better than boiling the teapot, because it takes both hot water and repetitive rinsing to get rid of the left over clay.
Many commercial grade factory-made teapots in 1990s and before would have tiny piles of dust and clays inside when they are new. Many higher grade of factory-made teapots in 190s and before would have piles of white, fine sands or even aluminum powders (both used to file the teapot opening) inside when they are new. In these cases, repetitive rinsing with hot water would work more effectively to remove the dusts and powders than boiling the teapot just once.
Sometimes, I would put some spent tea leaves in a teapot with water, and let it sit over night. This is because tea leaves are very absorptive, and could help to remove dusts hidden in the pores of the clay. I would prefer spent tea leaves to unused tea leaves, because the purpose is to use the absorptive feature of the tea leaves, and not to let the tea leaves "scent" the teapot - such scenting may disguise any residual dust odor and interfere with "sniff test".
4. Boiling the teapot in water.
Compared with method 3, boiling the teapot in water may get a teapot ready sooner (sometimes repetitive boiling and rinsing are probably necessary). It could work well on most new teapots (although many of the teapots don't need it), as long as carried out with caution. There are a few things that help to keep the teapot safe while being boiled:
a. Put the teapot in cold water before boiling starts;
b. Let all parts of the teapot completely submerged in water;
c. Leave lid off the teapot;
d. Use one or two towels to cushion the teapot in the boiling pot;
e. Use low heat when boiling;
f. After the heat is turned off, let the pot of water naturally cool down before taking out the teapot;
g Boiling the teapot for 30 minutes and 3 hours may do just the same work on the teapot, while 3-hour boiling induces more risk;
h. Some yixing teapots are waxed on the outside surface. Boiling (combined with scrubbing afterwards) could remove the wax relatively efficiently (compared with rinsing with hot water). But in such cases, you may need to spend extra time cleaning your boiling pot afterwards to get rid of any residual wax. If you are not sure whether the unusual shine on a yixing is caused by wax, you could try to scratch the teapot surface with fingernail and see if there is white wax accumulated.
When boiling a teapot, besides taking all above cautions, one should also be ready to take risk and, sometimes, take the consequences in following situations:
i. A high quality, well made zhu ni teapot may still have one or two tiny crackles (sometimes invisible by naked eyes or hidden in some invisible corner inside the teapot) that could be extended into severe damages by boiling
ii. Some older teapots could have tiny crackles or other tears-and-wears that could be extended into severe damages by boiling.
iii. Very often, boiling would remove a lot of (although not all) the "patina" on an older teapot. If your goal is to thoroughly remove all patina, boiling is not enough (harsher methods will be introduced in Part 2). On the other hand, if you don't want to lose a lot of the patina (given that it's known to be clean patina), then hot water rinsing would be better than boiling.
Chances of damage of the above two types could be minimized by taking cautious, but can't be completely avoided.
In part two, I will discuss:
4. rinsing cloth, luffa scrubb and tooth brush
5. tough detergent - bleach, hydrogen peroxide and other commonly used detergent for... toilet bowl...
6. relatively friendly detergent