I remember some eggs which the egg yolk is solid and black, but forgot the source(seems like preserved), what is it?(if any)

  • 1
    Probably spoiled?
    – Robert
    Sep 9, 2015 at 3:23

1 Answer 1


The current most common term in English appears to be "century egg", but it's also been known as a thousand-year egg or hundred-year egg.

It's typically produced by aging in a solution of table salt, calcium hydroxide, and sodium carbonate, but traditional methods involved less refined versions of those chemicals wrapped in clay (and some quantity of rice bran).

More details in this Wikipedia entry.

Century egg

Image: Wikipedia/Wiki commons

  • Is this that Asian egg that is fermented in urine?
    – Davor
    Sep 9, 2015 at 11:01
  • 3
    @Davor, this is the same egg. Except it was never produced using urine. It's a common misconception due to the fact that it smells like ammonia which is commonly associated with urine. It is traditionally made using ash as the agent that lowers its pH. Century egg needs a pH of 9-12 while urine can only raise it to about 7.5-7.9.
    – Jay
    Sep 9, 2015 at 12:55
  • Hence the dark, ashy color.
    – logophobe
    Sep 9, 2015 at 21:31
  • @Jay - I think that the fact that it's called "horse urine egg" in Thai has more to do with the misconception than the colour...
    – Davor
    Sep 10, 2015 at 10:42
  • @Davor You might be thinking of Virgin Boy Eggs en.m.wikipedia.org/wiki/Virgin_boy_egg
    – Preston
    Sep 12, 2015 at 2:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.