A painter in orange overalls touches up the image of a hand holding a rifle while an artist perched on scaffolding painstakingly places bits of colorful ceramic in a mosaic of a guerrilla fighter.
The artists aren't just decorating a wall: Together, they are helping to revive muralism, a movement that put Mexico at the vanguard of art a century ago.
Just as their famous predecessors did shortly after the Mexican Revolution, teachers and students of the Siqueiros School of Muralism are on a mission to keep alive the practice of using visual imagery to share messages of social and political importance.
The mural in progress is on three walls of a municipal building in San Salvador, a small town of about 29,000 people north of Mexico City in Hidalgo state. The Siqueiros School is based in a converted elementary school in the nearby hamlet of Poxindeje, and one of its co-founders is Jesús Rodríguez Arévalo, a pupil of disciples of Mexico's three muralism masters: Diego Rivera, David Alfaro Siqueiros and José Clemente Orozco.
"The school is small, a humble space, but it is very serious, and it is professional," Rodríguez said.
One hundred years ago, Rivera, Siqueiros and Orozco also started out at a colonial-era school-turned art laboratory. It was 1922, and they were charged with fulfilling the then-Mexican education minister's mission to take art out of the galleries and into public spaces. The plan, part of a national literacy campaign sponsored by the national government, transformed Mexico and permeated the entire continent.
The artists' manifesto was to make "ideological propaganda for the good of the people" and give art "a purpose of beauty, of education and combat for all."
They identified with the agrarian and proletarian revolutions and mingled with European artists who fled to Mexico from both world wars. Sponsored by the government, they had access to the country's most majestic buildings and the necessary resources to experiment with new techniques. Eventually, they began to paint in other nations: Argentina, Chile, Cuba and the United States among them.
Despite the backing of Mexican political leaders, their work turned out to be too provocative in some places outside the country: A mural Rivera painted in New York's Rockefeller Center was censured and then demolished because it glorified communism.
"We are a bit more cowardly," said Ernesto Ríos Rocha, 53, a muralist who is currently trying to found Mexico's first muralism university in the Pacific coast state of Sinaloa. "We talk more about peace."
The murals being created in San Salvador and other small towns today still have much in common with those created in the early 20th century, however: They encapsulate themes of war, injustice and oppression — as well as 21st century issues such as climate change and violence against women.
But Rodríguez and his students don't anticipate monumental reverberations from their work. Their aspirations are lower and their income more modest, coming mostly from local governments that commission them to paint murals and support from community members who donate meals and house foreign students.
The Poxindeje school bets on recycling and reusing discarded materials donated by glassmakers or flooring manufacturers, said Janet Calderón, who co-founded the Siqueiros School with Rodríguez five years ago. They're even making murals from garbage.
Luz Asturizaga, a 36-year-old sculptor from Bolivia, has enjoyed every moment of her stay in the iconic home of muralism. She wasn't able to learn much about the art form in her own country, where she said professional artists' circles are very closed. In Mexico, "they give you opportunity, they teach you," she said.
Few students have completed training at the school — about 40 since it opened five years ago — but all leave with clear ideas instilled by their instructors: "Go to the communities, teach, carry out a comprehensive work of historic themes, of social content, of criticism of everything that oppresses man," Rodríguez said.
The first step for the artists is to decide what elements they want to include, what metaphors to lay out. Then they build a sort of collage of portraits and photographs of historical figures whom they want to immortalize.
Composition and perspective are key. Dressed in paint-splotched jeans, his black hair tied back in a ponytail, the 54-year-old Rodríguez closes one eye in front of the mural in progress in San Salvador, and with the other glances through a transparent sheet of paper containing sketches of figures intended for the wall. The goal is to calculate the right scale, taking into account from where and what distance people will be viewing the work.
"You have to know local history and then begin with the sketches," said Luis Manuel Vélez, 52, a worker for Mexico's national oil company who spends his weekends painting murals.
Sometimes models for the work come from the neighborhood. A 6-year-old girl passing by the mural in San Salvador pointed and smiled before exclaiming: "That's me and my grandpa."
Purists have long lamented that starting in the late 20th century, muralism was replaced by urban art or short-lived graffiti.
Ríos Rocha agrees but is still optimistic.
"Muralism is in intensive care, but it is not going to die," he said.
Historian David Martínez Bourget is a researcher at the 88-year-old Bellas Artes Museum, a palatial art nouveau performing arts center in Mexico City whose interior walls are graced with famous murals by Rivera, Siqueiros and Orozco.
Martínez Bourget said the art movement that the fathers of muralism began in the 20th century is over, but its spirit remains — not just in Poxindeje and San Salvador — but also in marginalized Chicano communities in the western United States and in Zapatista villages in southern Mexico. In both places, public art displays capture the communities' history and rebellion, he noted.
As long as people are fighting for social justice, this kind of artistic expression will exist, Martínez Bourget says, because in difficult moments "art is politicized."