The aim of dyeing is to make uniform colouration of a substrate. The colour should be uniform; it means that it should be a solid shade with no change in the shade over the whole substrate. There are many parameters affecting the appearance of the final shade including substrate’s texture, physical and chemical construction of substrate, pretreatments and post treatments applied after the dyeing process.

The substrates may be divided into two major classes: hydrophilic and hydrophobic. Examples of hydrophilic fibres are cotton, wool, silk and etc. synthetic polyester, acrylics, polyamides and polyolefin fibres are some examples of hydrophobic substances.