Wool is the most common natural yarn used in carpets. It is soft and hard wearing, although it is susceptible to mould. While an attractive option as a carpet material, it is notably more expensive than synethetic options, meaning that it is generally only used in more luxurious carpets. It is the yarn of choice for many handmade carpets; handmade Persian carpets, for example, predominantly use wool for the carpet’s pile, while using cotton for the warp and weft.