What is the name of the red paper used to write riddles

Chengdan paper, this paper is dyed with red dan color, which is characterized by not easy to fade, the red dan used by grinding, plus glue color, two people together dyeing, baked with charcoal, baked when the fire surface covered with grass ash, to prevent the flames from roasting the paper. This paper with jade buckle paper is good. Fine workmanship, strict requirements, production is not high. In the past, the average person a day only 400 ~ 500 sheets of dyeing, this paper is generally used for more refined supplies, such as book covers or paintings bookmarks and so on. Chinese antique wire-bound books with this paper for the title page, in addition to decorative, but also anti-moth-eaten function, the protection of books has a special effect. Bright red color is not easy to fade. Sprinkled with silver foil or copper and tin foil on the surface of Zhengdan paper is called "silver doped", which makes the paper dotted with gold stars and is more distinctive. The "silver mixed" Zhengdan paper is mostly used for covers or couplets. As long as the color is not easy to fade, there is a "perpetual red" or "never fade" of the name.