They only painted the first layer fo poaint.

他们刚刷了第一层油漆。

Taking small samples from the added and original paint layers, they analyzed the compositions of each.

他们从添加的和原始的油漆层中抽取少量样本，分析了每个油漆层的成分。

This is particularly challenging as the inner paint layers may have already dried when adding a new wet layer on top of them.

这项功能非常有挑战性，因为可能会出现底层的颜料已经干了，用户才画新的一层湿颜料在上面。

If you see the underlying paint layers for example, the underpaint, he really put on kind of fast and rough brush strokes to define light and shadow.

如果你们看下面的油漆层，比如底漆，他其实用了一种快速且粗糙的笔触来定义光与阴影。