He knew that this undercoat would be better at reflecting light.

他知道这种底涂层会更好地反射光线。

He then applied a series of undercoats, letting them dry before applying another.

然后，他涂一系列底漆，等它们涂另一层。

But for many mammals, hair grows in two layers consisting of a shorter undercoat of ground hairs covered by longer guard hairs.

许多哺乳毛发生长为两层，由较短毛作为底层毛发，上面覆盖较长保护毛。

For Mona Lisa, he used a thin-grained piece of poplar tree and applied an undercoat of lead, white.

在创作《蒙娜丽莎》时，他使用一棵纹理很薄白杨树，并涂一层白色铅底漆。

The lead white undercoat reflects the light back through his glazes, giving the picture more depth, and in essence, lighting Mona Lisa from within.

铅白色底漆将光线通过釉料反射回来，使这幅画更有深度，从内部照亮《蒙娜丽莎》。