Bhutanese produce special manuscripts with illuminations. The paper for the illuminated manuscripts are often dark blue or black in colour according to the need. For illuminated manuscripts, at least two sheets of paper are glued together to create a thick and durable sheet. This is then either dyed in paint or applied dark blue or black paint with a brush. The colour used is often indigo but a range of materials including azurite, myrobalan, nutmeg, borax are also used and torquoise and lapis are also said to be used for colouring the paper. The coloured paper is then polised using a conch shell or a smooth stone.