A nice essay about Frankenthaler’s breakthrough technique here:
Through her soak-stain technique the canvas and paint became one, emphasizing the flatness of the painting even while they conveyed great space. Through the thinning of the paint, “it melted into the weave of the canvas and became the canvas. And the canvas became the painting. This was new.” (2) The unpainted areas of the canvas became important shapes in their own right and integral to the composition of the painting.
There is also a brief discussion of whether or not “beauty” is an asset in a modern work:
Frankenthaler responded, “People are very threatened by the word beauty, but the darkest Rembrandts and Goyas, the most sombre music of Beethoven, the most tragic poems by Elliott are all full of light and beauty. Great moving art that speaks the truth is beautiful art.”
Abstract Painting: Concepts and Techniques has a chapter on various stain techniques and practitioners.