In more recent times, the century egg is made by preserving it with sodium and alkaline hydroxide. They gradually raise the pH of the egg to 12 or more, resulting in the breakdown of the complex, flavorless proteins and fats in the egg, producing a number of smaller strongly flavored compounds. The main agent responsible for these transformations in a century egg are the alkaline materials in it.

The egg white too becomes a dark brown colored translucent jelly, having a salty flavor. It also acquires a strong odor of sulfur and ammonia. The lime causes the egg to age faster, and its yolk turns into a dark green to gray color, and develops a creamy consistency. During this period, certain important chemical reactions take place within the egg. The mud in the coating mixture slowly dries and hardens over time. The eggs thus coated are placed inside a cloth-covered jar or wooden basket. Each egg is individually coated with lime, ash and clay, and then rolled in a mass of rice hull to prevent it from sticking to the other eggs.

Traditionally, it is made by preserving duck eggs, quail eggs, or chicken eggs, by wrapping them inside plaster coating made from a mixture of clay, ash, salt, quicklime, and rice hull, for several weeks to several months. The century egg is an ancient Chinese delicacy. Many claim that it has a number of added health benefits too as compared to normal eggs. Though it may seem odd, the century egg is actually considered an exotic delicacy in Asia.

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