The pulp used as the raw material of paper is generally bleached, for otherwise paper would not be white and colour printing would result in muddy colours. Traditionally, pulp has been bleached with chlorine, but because it is regarded as harmful to the environment, other methods have also been developed. Chlorine bleaching is only used in making EFC pulp (Elementally Chlorine Free), which means that the bleaching uses chlorine dioxide instead of elemental chlorine. TCF pulp (Total Chlorine Free) means that no chlorine or chlorine compounds have been used in bleaching. Oxygen bleaching is a method in which the bleaching is started with oxygen, which is followed by 4 to 5 other bleaching stages. In enzyme bleaching, the pulp first undergoes intensive boiling and oxygen bleaching, after which it is first bleached with enzymes and only after that comes the actual bleaching with other bleaching chemicals. In peroxide bleaching, the pulp is bleached with hydrogen peroxide, which reduces or completely eliminates the need for chlorine bleaching.