Boiled eggs are eggs (typically chicken's eggs) cooked by immersion in boiling water with their shells unbroken. Eggs cooked in water without their shells are known as poached eggs. Hard-boiled eggs are either boiled long enough for both the egg yolk and the egg white to solidify, or they left to cool down, which of itself solidifies them, while a soft-boiled egg's yolk, and sometimes even the white, remains at least partially liquid. The egg timer was so-named due to its common usage in timing the boiling of eggs.

    Soft-boiled eggs
    Soft-boiled eggs are typically cooked by placing the eggs in a pan of boiling water and then simmering.[1] British cook Delia Smith suggests placing an egg in cold water, bringing to the boil, and simmering: 3 minutes for a very soft egg, 4 minutes to make sure the white is set, and 5 minutes for an almost-set yolk.

    Soft-boiled eggs are not recommended for people who may be susceptible to salmonella, such as very young children, the elderly, and those with weakened immune systems.

    Serving
    Soft boiled eggs are commonly served in egg cups, where the top of the egg is cut off with a knife or egg scissors, using a teaspoon to scoop the egg out. Other methods include breaking the eggshell by tapping gently around the top of the shell with a spoon.[4] Soft-boiled eggs can be eaten with buttered toast cut into strips, which are then dipped into the runny yolk. In the United Kingdom, these strips of toast are known as Soldiers.[5]

    Hard-boiled eggs
    Hard-boiled eggs are boiled for longer than soft-boiled eggs, long enough for the yolk to solidify.[6] They can be eaten warm or cold. Cold hard-boiled eggs can be chopped up to form the basis for egg salad. Hard-boiled eggs can also be eaten warm in an egg cup.

    There are several theories as to the proper technique of hard-boiling an egg. One method is to bring water to a boil and cook for eight minutes. Another method is to bring the water to a boil, but then remove the pan from the heat and allow eggs to cook in the gradually cooling water.[7] Others prescribe cooking in continually boiling water over heat for a shorter period of time.[6]

    Over-cooking eggs will typically result in a thin green sulfur coating on the yolk. Immersing the egg in cold water after boiling is a common method of halting the cooking process to prevent this effect.[7] It also causes a slight shrinking of the contents of the egg, easing the removal of the shell.

    Hard-boiled eggs in their shells can be stored in the refrigerator for days to weeks.

    白煮蛋指的是未剝殼的蛋（一般指雞蛋）浸沒在沸水中而煮熟的蛋。而水煮的去殼的蛋稱為水煮蛋.煮得老的雞蛋既非煮得足以使蛋黃和蛋清都凝結成形，亦非使之冷卻后自凝;而半熟的雞蛋的部分蛋黃甚至是蛋白是液體狀的。煮蛋計時器也是因去用途而得名。

    半熟的雞蛋

    半熟的雞蛋一般是指放在一平底鍋內沸水慢慢煨而煮出來的蛋。英國廚師迪莉婭史密斯建議把雞蛋放在冷水中煮，到水開時用文火煨，三分鐘后就有一個半數的蛋了，4分鐘能使蛋清成形，5分鐘蛋清蛋黃就幾乎全成形了。

    但是半數的蛋并不適合那些可能對沙門氏菌過敏者，像小孩子，老人以及免疫力低下著。

    吃法

    半熟的蛋通常用蛋杯盛放，蛋的頂部被刀或蛋剪刀切開，然后用一個茶勺把蛋挖出來就可以吃了。還有別的方法，比如用勺子輕敲蛋殼頂部。半熟蛋可以和切片黃油吐司一起吃，因為后者會浸沒在流體狀的蛋黃中。在英國，這樣的切片吐司稱為“士兵”。

    煮得老的雞蛋

     老雞蛋煮得比半熟蛋足夠久，因而其蛋黃能凝結起來，可以趁熱吃也可以做冷菜。它可以冷卻后剁碎做蛋沙拉的料底，也可以趁熱放入蛋杯內享用。

    至于適合煮老雞蛋的方法，這里有多種說法。一個是說把蛋和水一起燒開，煮8分鐘。另一個說是水燒開后移開鍋子停止加熱，用水的余熱繼續煮蛋。還有人給出說法，說是把蛋放入沸水中加熱一小會兒。

    煮過頭的蛋的蛋黃表面通常有薄薄的一層硫磺色的衣，為了避免這層衣的出現，人們常常在煮完蛋后把它浸沒在冷水中，這樣一來蛋白和蛋黃也會輕微收縮，剝起來更容易。

    未剝殼的老雞蛋可以放入冰箱中保存幾天到幾周。