1. Paint the paper with Pu 'er tea, and it will turn yellow and old in a few days.
2. Soak or spray new paper several times with 1% ferric chloride solution. A week later, the color of the paper turned yellow. After a period of time, the paper turns yellow, slightly gray and feels like old paper.
3. Irradiate the new paper with ultraviolet rays for 2-5 days to make the new paper feel similar to the old paper, and then dye it with gamboge to become the old paper.
4. Boil a pot of boiling water, tie the four corners of the paper firmly, 20 cm away from the water to make it evenly wet, and repeat it two or three times on both sides. Dry in the sun.
Squeeze into old books for two days, and then put them in humid air for two days, so they look old after drying.