Tonight in Drawing Class I gave a brief explanation of what all those numbers mean on the ends of your pencils, why you would choose one over the other and why it matters. I touched briefly on the concept of surface "tooth" and grain.
To illustrate the point, I used one of Boy2's toy cars with different pencils clipped to it to draw lines across a page. This demonstrates how the darkness of the pencil varies while the working pressure remains relatively constant, thus preserving "tooth".
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