LOS ANGELES — Volunteers began launching thousands of hand painted vinyl balls into the lake at MacArthur Park Friday as part of a large-scale public arts installation spearheaded by a local arts organization.

The volunteers will be working through the weekend to piece together “Spheres of MacArthur Park,” which involves filling up the 8.39-acre lake with about 3,000 balls, each 4- to 6-feet in diameter and covered in bright floral and fish patterns.

Ed Massey, co-founder of the Santa Monica-based nonprofit Portraits of Hope, which organized the effort, estimates the installation will be ready for public viewing by Monday. He said the group could use some extra volunteers this weekend, preferably high-school-aged or older, to help with prepping and installing the balls.

The spheres will be in place for a four-week run, during which time another 3,000 balls or so will be introduced into the lake every five days or so to relieve the first set of spheres being installed this weekend, Massey said.

After the exhibit closes, the spheres will be donated to schools, hospitals and other organizations, he said.

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The vinyl, beach-ball-like orbs were painted by hand earlier this summer by about 10,000 volunteers, including hospital patients, students from nearby schools and youth who took part in the Special Olympics, Massey said.

Portraits of Hope has done similarly ambitious public arts projects over the past 15 years, including a painted blimp that was flown over 10 states, thousands of New York taxicabs decorated in bold florals, and lifeguard towers splashed in colorful, geometric patterns along 31 miles of Los Angeles beaches.

Massey said these massive, public arts installations and the latest one at MacArthur Park give youth who “normally don’t have an opportunity to transform a cityscape” an opportunity usually reserved for well-known architects.

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He said he hopes the spectacle of the cheerfully painted, giant balls floating and turning in the lake will bring “a little tender love” to MacArthur Park, an iconic but occasionally forgotten public space in Los Angeles.

“This will be the launching of good energy and good vibes,” he said.

Massey noted that previous such projects have drawn out musicians, and he hopes the same will happen at MacArthur Park, possibly with jazz musicians adding a soundtrack to the moving spheres.

Anyone interested in helping with this weekend’s installation can reach the nonprofit by emailing poh@portraitsofhope.org or by calling 310-951-5936.