Appropriate line thickness depends very much on what sort of drawing you want to do. If you are aiming for realism, lines should be eliminated to the greatest extent possible, as there are no lines in real life only blocks of different values or colours either gradually gliding into each other or starkly placed next to one another.
If realism is not your goal, and you want to have a more graphic approach then thouhts about line thickness, or line weight as it is often called, are essential. In the words of Tom Richmond, cartoonist on the MAD magazine:
"Certain stylistic approaches aside, there is very little that is more boring than a line with no variation. It’s flat and lifeless. We discussed using line thickness to help establish a light source and to help separate forms in part one, but line variation is so much more than that. It’s visual interest and dynamics. It gives a drawing life, movement and energy. Line wieght adds mass, form and a substantial quality to a two-dimensional image.... Total logic with respect to line variation isn’t necessary. Sometimes you add weight to a line to make something seem heavier or more substanial, or to place it solidly in front of another object, or to emphasize a light source… but sometimes you do it just to add some interest to the drawing. Ink blobs, too-wet-lines and other accidents can often be “happy accidents” because the spontaneously add some interest to a drawing that might otherwise be very sterile. Where you place your thick and thin lines depends greatly on your own drawing style and sensibilites. "
From his blog.I love the line - and I love to see drawings and paintings done with lines. Like this one:
Click to view attachment(
Copyright Catherine Karina Chmiel)
See how the line comes and goes? And how it is thicker in some places, like on the woman's neck and the child's fist, to underscore their characters, but also appropriate to where the lightsource is. And this is, I feel, actually a rather subtle use of line, you can be far more heavy with the lines and still get away with it. There are no rules. It can be a stylistic choice to outline everything in thick heavy lines, but it does seem that many agree that it is useful to vary the line weight because it helps guide your wiever's eye around the drawing. You can manipulate with it, suggest light and shadow, and areas of interest. If you like lines, by all means use them! Experiment, and if you like, come back to show us what you have done, and if you need help we're here for that too.
Happy drawing.