Albumen accounts for most of an egg's liquid weight, about 67%. It consists of four opalescent layers of alternately thick and thin consistencies. The white of a freshly laid egg has a pH between 7.6 and 7.9 and an opalescent (cloudy) appearance due to the presence of carbon dioxide. As the egg ages the CO2 escapes which increases the pH. Egg white also becomes thinner as an egg ages because its protein changes in character. That's why fresh eggs broken onto a plate sit up tall and firm while older ones tend to spread out. The albumen of older eggs is more transparent than that of fresher eggs. Fresh egg whites coagulate in the range 62° to 65°C, the temperatures decrease with increasing pH and hence age. This is why very fresh eggs require more time to cook than older eggs.