The boys saw a stream of chemicals shoot out of the machine and spray the metal ball.

男孩们看见一股化学试剂从机器喷里喷出，洒在金属球上。

To ensure the conditions are safe, every evening after closing, Navy Pier staff spray the plastic balls with a special cleaning solution.

为确保安全，每天晚上闭馆后，海军码头的工作人员会用特殊的清洁剂喷洒塑料球。