Question

how many years was silk
kept as a secret by Chinese​

Answer 1

two thousand years

For more than two thousand years the Chinese kept the secret of silk altogether to themselves. It was the most zealously guarded secret in history. Chinese legend gives the title Goddess of Silk to Lady Hsi-Ling-Shih, wife of the mythical Yellow Emperor, who was said to have ruled China in about 3000 BC.