Century Eggs being peeled on a wooden board
You Can Actually Make Century Eggs In The Comfort Of Your Home
By Annie Hariharan
Century eggs, a.k.a. millennium eggs or black eggs, are traditionally made by curing raw duck, chicken, or quail eggs in a paste of salt, quick lime, and ash before rolling them in rice husks. To make them in your home, you can either stay as close as possible to the traditional ingredients or break out those protective gloves and household chemicals. 
For the traditional approach, mix rice hulls, clay ash, lime powder, and salt in an earthen pot, then add the duck eggs, covering them completely with the mixture. Cover the pot, and keep it in a dry, dark area for six to eight weeks — if you do not have clay ash, use a mix of clay or wood ash.
Option two requires making a pickling solution from salt, lye (aka caustic soda), and water, then submerging the eggs in the pickling solution for about 10 days. Remove and pat dry before encasing it in modeling clay that won’t break when dry for another two to three weeks to prevent oxidizing.