This is ash from your lye that arises from the wood on the Cham Islands which can be about 12 kilometers with the Coastline of Hoi An. You will discover far more comprehensive workshops where you will learn to make the lantern from the to Z, like developing the frame. https://jeffreygkklj.bloggazza.com/34150088/a-simple-key-for-hoi-in-an-unveiled