Question: What was strongest in the early movement with Rivera, Orozco and Siqueiros all avowed communists?
About the article "Mexican muralism", section "Artistry".

Candidate passages:
Orozco Rivera was a student and apprentice to David Alfaro Siqueiros, a later proponent of the Mexican muralism movement, faithfully adhering to the aesthetics and ideology of social realism.
His artistic work; oils, sculptures and murals show strong influence from Siqueiros, with the most common themes being the struggles of common and marginalized peoples, done without portraying anyone in particular, using composite faces.
He considered painting to be a social contract and preferred painting murals over easel works “which are sold in galleries like merchandise.” He did not believe in art for its own sake, rather that it was fundamentally social and communicative.
He stated he painted to express what he had inside, not for pleasure. 
Mario Orozco Rivera (b. January 19, 1930 – d. November 20, 1998 was a Mexican muralist and painter, a later proponent of Mexican muralism, and whose work was particularly influenced by David Alfaro Siqueiros.
He created a number of murals, mostly in the state of Veracruz before becoming an assistant to Siqueiros, directing the Taller Siqueiros in Cuernavaca and working with the artists on projects such as the Polyforum Cultural Siqueiros.
While preferring mural work, which he considered less commercial, Orozco Rivera also created oils and sculptures.
Many of these works were exhibited in Mexico and abroad and can be found in many major collections.
His work received recognition in various countries. 
José Clemente Orozco, Fernando Leal, David Siqueiros and Diego Rivera the famous Mexican artists, renewed the art of fresco painting in the 20th century.
Orozco, Siqueiros, Rivera and his wife Frida Kahlo contributed more to the history of Mexican fine arts and to the reputation of Mexican art in general than anybody else.
Together with works by Orozco, Siqueiros, and others, Fernando Leal and Rivera's large wall works in fresco established the art movement known as "Mexican Muralism".
Among contemporary artists, Fernando Leal Audirac has developed a technique of transportable frescos. 
Mexican populist art production from the 1920s to the 1950s is often grouped under the name of “Escuela Mexicana de Pintura (y Escultura) (Mexican School of Painting and Sculpture), coined in the 1930s by art historians and critics.
The term is not well-defined as it does not distinguish among some important stylistic and thematic difference, there is no firm agreement which artists belong to it nor if muralism should be considered part of it or separate.
It is not a school in the classic sense of the word as it includes work by more than one generation and with different styles that sometimes clash.
However, it does involve a number of important characteristics.
Mexican School mural painting was a combination of public ideals and artistic aesthics “positioned as a constituent of the official public sphere.” Three formal components of official Mexican muralism are defined as:1) Direct participation in official publicity and discourse2) Reciprocal integration of the visual discourse of the mural to an array of communicative practices participant in defining official publicity (including a variety of scriptural genres, but also public speech, debate and provocative public “event”)3) The development and public thematizing of a social-realist aesthetic (albeit multiform in character) as the visual register for the public sense of the mural work and as the doxic, or unquestioned, limits for public dispute over the representational space of the mural imageMost painters in this school worked in Mexico City or other cities in Mexico, working almost uninterrupted on projects and/or as teachers, generally with support of the government.
Most were concerned with the history and identity of Mexico and politically active.
Most art from this school was not created for direct sale but rather for diffusion in both Mexico and abroad.
Most were formally trained, often studying in Europe and/or in the Academy of San Carlos.
A large quantity of murals were produced in most of the country from the 1920s to 1970, generally with themes related to politics and nationalism focused often on the Mexican Revolution, mestizo identity and Mesoamerican cultural history.
These served as a form of cohesion among members of the movement.
The political and nationalistic aspects had little directly to do with the Mexican Revolution, especially in the later decades.
The goal was more to glorify it and its results as a means to legitimatize the post Revolution government.
The other political orientation was that of Marxism, especially class struggle.
This was strongest in the early movement with Rivera, Orozco and Siqueiros all avowed communists.
The political messages became less radical but they remained firmly to the left.
Much of the mural production glorified the indigenous aspect of Mexican culture, considering it an important factor in the creation of modern Mexico.
This was added with the idea of reexamining the country’s history from a different perspective.
One other aspect that most of the muralists shared was a rejection of the idea that art was only for the elite, but rather as a benefit for the masses.
The murals took on monumental status because of where they were situated, mostly on the walls of colonial era government buildings and the themes that were painted.
The mural painters of Mexico freely shared ideas and techniques as they were a closely knit group.
However, the work of each was distinctive as the government did not set style and artists can generally be deduced without looking at signatures.
Techniques included the revival of old techniques such as the fresco, painting on freshly plastered walls and encaustic or hot wax painting .
Others used mosaics and high fire ceramics, as well as metal parts, and layers of cement.
The most innovative of the artists was Siqueiros who worked with pyroxlene, a commercial enamel and Duco (used to paint cars), resins, asbestos, old machinery and was one of the first to use airbrush for artistic purposes.
He pored, sprayed, dripped and splattered paint for the effects they created haphazardly.
By far, the three most influential muralists from the 20th century are Diego Rivera, José Clemente Orozco and David Siqueiros, called “los tres grandes” (the three great ones).
All believed that art was the highest form of human expression and a key force in social revolution.
Their work defined the movement taking over from Vasconcelos.
It created a mythology around the Mexican Revolution and the Mexican people which is still influential to this day, as well as promote Marxist ideals.
At the time the works were painted, they also served as a form of catharsis over what the country had endured during the war.
However, the three were different in their artistic expression.
Rivera’s works were utopian and idealist, Orozco’s were critical and pessimistic and the most radical were those of Siqueiros, heavily focused on a scientific future.
The differences among the three have much to do with how each experienced the Mexican Revolution.
Rivera was in Europe the entire time and did not fight.
He never depicted the horrors of the war but what he perceived to be the social benefits from it.
The other two did and both did express the horrors of war in their work.
There was resentment to Rivera by the other two because of it, especially from Siqueiros.
Of the three, Rivera was the most traditional in terms of painting styles, drawing heavily from European modernism.
In his narrative mural images, Rivera incorporated elements of cubism His themes were Mexican, often scenes of everyday life and images of ancient Mexico.
He originally painted this in bright colors in the European style but modified it to more earthy tones to imitate indigenous murals.
His greatest contribution is the promotion of Mexico’s indigenous past into how many people both inside and outside of the country view it.
Orozco also began with a European style of expression.
However his art developed into an angry denunciation of oppression especially by those he considered to be an evil and brutal rules class.
His work was somber and dire, with emphasis on human suffering and fear of the technology of the future.
His work shows an "expressionist use of color, slashing lines, and parodic distortions of the human figure."
Like most other muralists, Orozco condemned the Spanish as destroyers of indigenous culture, but he did have kinder depictions such as that of a Franciscan friar tending to an emaciated indigenous period.
Unlike other artists, Orozco never glorified the Mexican Revolution, having fought in it, but rather depicted the horrors of this war.
It caused many of his murals to be heavily criticized and even defaced.
Siqueiros was the youngest and most radical of the three.
He joined the Venustiano Carranza army when he was eighteen and experienced the Revolution from the front lines.
Although all three muralists were communists, Siqueiros was the most dedicated, as evidenced by his portrayals of the proletarian masses.
His work is also characterized with rapid, sweeping, bold lines and the use of modern enamels, machinery and other elements related to technology.
His style showed a "futurist blurring of form and technique."
His fascination with technology as it relates to art was exemplified when he emphasized the mass communications visual technology of photograph and motion picture in his eventual movement toward neorealism.
His radical politics made him unwelcome in Mexico and the United States, so he did much of his work in South America.
However, his masterpiece is considered to be the Polyforum Cultural Siqueiros, located in Mexico City.
The Big Three struggled to express their leftist leanings after the initial years painting murals under government supervision.
These struggles with the post-revolution government lead the muralists to create a union of artists and produce a radical manifesto.
The Secretary of Public Education under Obregon contracted Rivera, Siqueiros, and Orozco to pursue painting with the moral and financial support of the new post-revolutionary government.
Vasconcelos, while seeking to promote nationalism and “raza cosmica,” seemed to contradict this sentiment as he guided the muralists to create works in a classic, European style.
The murals became a target of Vasconcelos’s criticism when the Big Three departed from classical proportion and figure.
Siqueiros was dissatisfied with the incongruity between the murals and the revolutionary concerns of the muralists, and he advocated discussion among the artists of their future works.
In 1922 the muralists founded the Union of Revolutionary Technical Workers, Painters, and Sculptors of Mexico.
The Union then released a manifesto listing education, art of public utility, and beauty for all as the social goals of their future artistic endeavors.