 Their roots contain a slimy mucus (called Dak Pul) which helps hold the paper together and give viscosity to the bark.Ancient Koreans usually started making Hanji during the winter, because the mucus from "Abelmoschus manihot" became easily fermented due to the summer heat.Ancient Koreans believed that it was important to choose a good day with a nice sky to start making Hanji, and often gave religious rituals to the spirits in order to wish for a favorable condition and a smooth process.