Geisha's (engertainer) and Yuujo's (prostitute) painted their teeth black, and this ritual was called Ohaguro.
About the ritual Ohaguro
top from the left：rice syrup, salt, mirin, sugar
bottom from the left: rice mold, rusted metal, tea leaves
I needed 20 pieces of rusted metal nail. I had to get them from our ceiling that was built around 100 years ago.
burn the nails
and throw them in the hot tea water
Let them ferment for 3 mth. When it starts to stink, it's ready! Paint the teeth with this liquid and Fushiko (powder made from urushi tree bump that contains a lot of tannin)
The principle of enamel: chemical reaction of metal & tannin.