Painting on water also known as Paper Marbling

Source: youtube channel funfunfunfunfunfive, wikipedia

"Paper Marbling is a method of aqueous surface design, which can produce patterns similar to smooth marble or other stone. The patterns are the result of color floated on either plain water or a viscous solution known as size, and then carefully transferred to an absorbent surface, such as paper or fabric. Through several centuries, people have applied marbled materials to a variety of surfaces. It is often employed as a writing surface for calligraphy, and especially book covers and endpapers in bookbinding and stationery. Part of its appeal is that each print is a unique monotype."

The history of Paper Marbling is said to originate in different parts of East Asia. Known to be used in China, Persia, Ottoman Turkey, in Islamic Empires then Europe.