Artists from the Abstract Expressionist movement were known for their 'expression of emotions'. I'll discuss the replicas of Clyfford Still and the series of Motherwell, de Kooning, and others.

The roots of the art movement known as Abstract Expressionism (aka the New York School) began in post WWII America during the 1940s-1950s.

Artist Clyfford Still (1904-1980) created 'replicas' of his work because he wanted a 'personal record' of paintings sold, lost, or destroyed, and to provide additional versions.
The definition of replica is an "exact reproduction" as it was executed by the original artist.

An exhibit, "Repeat/Recreate: Clyfford Still’s 'Replicas'" displaying 16 of his paintings and replicas side-by-side, were shown at the artist’s museum in Denver, CO.

There presently exist 59 sets of Still’s replicas (some in US museums) which appear to be painted in difference size canvases.
In 2011 Sotheby’s auctioned four of Still’s paintings. Two of them: "1949-A-No 1" sold for $61.6 m, and "1947-Y-No.2" sold for $31.4 m. The CS Museum has a replica of both.

Clyfford Still Museum director Dean Sobel stated, "Replication is the basis of Abstract Expressionism as a whole."

Still’s paintings "1944-N No 2" and "1944-N No 1" are identical in character and quality. You can view "1944-N No 2," also titled "Red Flash on Black Field" at the Museum of Modern Art, NY.

Note: 'copies' of paintings (by someone other than the primary artist) are required to be of different dimensions than the original to insure it is not sold as the original.

Although Robert Motherwell’s "Elegy to Spanish Republic" series - 100 black and white paintings (1948-1967) refers to the Spanish Civil War (1936-1939) – the artist claims they are not political.

Willem de Kooning's "Women Series" can be simply described as 'caricatures' of women. They are a far cry from the classical paintings of Odalisque by Ingres.
His first painting in the series, "Woman I" (1950-1952) can be viewed at the Museum of Modern Art, NY.

Serial paintings by Barnett Newman (1905-1970) all contain what is known as the "zip" - a vertical band of color in the center of the painting - meant to merge both sides, not separate them.

The "zip" has been compared to Alberto Giacometti’s slender figures in his sculptures. [That is a stretch of the imagination].

Cy Twombly’s "Blackboard Series" (1966-1970) were meant to represent a classroom chalkboard with white swirling markings.
The last in the series, "Untitled" (1970) was auctioned at Sotheby’s NY in 2012 for $174 m.

As the museum goer, you may not understand what the abstract expressionist artist is trying to convey, but you must respect the mood and work behind the paintings we have known to love.

You can own the hardcover book, "Robert Motherwell" by H.H. Arnason, available here from Amazon.com.