How to reflect the material of plaster sketching

First of all, we need to understand the material characteristics of plaster: delicate, white, hard, light and brittle, so the heart should be fine when drawing, the hand should be careful, try not to draw too rough. Lines should be fine and neatly arranged, with a hard pencil, do not draw too gray, try to bright surface, bright gray surface do not draw over, light and dark in the structural line and the intersection of light and dark line, to contrast strongly and surely, reflective surface is also the key, pay attention to the treatment of reflective surface. The most important thing is to carefully observe the contrast when painting, paint more, observe, naturally show the material of the plaster.