The purpose of this post is not to talk about drawing as a whole. It is to talk about pencil drawing as it relates to watercolor painting.
Any artist will tell you that it’s better to be discriminating with how you lay down your lines than it is to just draw them all the same way, like a bad Sunday cartoon. What that means is that any line you lay down will have a certain weight, darkness, or boldness, depending on how hard you press your pencil. Look at my final drawing of the rhinoceroses: just above the baby’s back, you see wrinkle lines much fainter than the line between the two rhinos. This creates a hierarchy of importance, and helps push the baby rhino forward.
Line weight serves another function in watercolor painting. Because watercolor is transparent (meaning you can see through a layer to what’s beneath it) pencil lines will stay visible in the finished painting…unless you only draw the lines where there are hard edges between light and dark. In that case, the masses of dark/light, positive/negative, and background/foreground make the pencil line disappear.
So, if you have an edge between two contrasting masses, that can be a dark, hard line. But if you have a line delineating a soft edge, like a form shadow, that line should be lighter so that it won’t appear in the final painting. By consciously controlling your line quality, it will be possible to improve your painting, because the lines signal your brain to treat different edges different ways.