参考译文：这些泪水在眼睛的表面形成一层薄膜。
因为暴露在空气中，所以在糖浆的表面，形成了一层薄膜。
Because a thin film has formed on the surface of the syrup due to its exposure to air.
难熔金属和贵金属组合的这一层薄膜使刻蚀成为一个艰巨任务。
The combination of refractory and noble metals in a single layer makes etching a formidable task.
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