It was at this time that manuscripts began to be painted in grisaille .

正是在这时候，手稿开始被画在。

Grisaille : painting technique by which an image is executed entirely in shades of gray and usually modeled to produce the illusion of sculpture or relief .

灰色单色画完全用灰色浓淡变化描绘形象，通常多突出立体感，以形成类似雕塑，特别是浮雕的视觉效果的绘画技法。