What does it mean to collect ash from tea leaves?

This is a process of making tea. That is to say, the fried Longjing tea is wrapped in paper and put in a lime jar for half a month. This is not a simple release, but let lime absorb the astringency of Longjing tea and increase the fragrance. It can be said that Longjing without the ash collection procedure is not the real Longjing in the traditional sense.