A kneaded eraser consists is a soft, pliable rubber mass which can be shaped into any desired form in a similar way as dough. However, Kneaded erasers are not used for erasing in the traditional sense. Instead, the rubber mass is pressed onto the spot in order to absorb some of the applied graphite or charcoal particles.
The stronger you press the kneaded eraser onto the paper the more particles are removed. In general the surface is only lightened and not completely whitened because the pencil lines cannot be fully removed with a kneaded eraser.
On the other hand, you will not damage the drawing surface in any way. Even a lot of pressure will not harm it because the eraser is pliable.
How to use the kneaded eraser in drawings
This little tool is often used to adjust dark areas or to create bright highlights. A kneaded eraser is particularly useful for drawings with charcoal and pastel chalk as the pigment only loosely adheres to the paper.
In contrast to conventional erasers it does not lose any volume because it does not rub off.
However, due to the constant reshaping and the absorption of the pigment, it cannot be used for all too long before its efficiency starts declining. When you notice the surface of the eraser turning dark then it is time to stretch the mass, knead it a bit, and form the shape you are using again.
Here is a helpful tutorial on how to do that and when you should notice that the eraser can’t hold anymore graphite or charcoal and thus should be replaced:
Examples of those principles applied
Take a look at the Smile with teeth drawing tutorial. In order to emphasize the accents further I erase the light reflected from the teeth with the kneaded eraser.
Since these areas were only softly filled with a HB pencil and then softened with a blending stump the bright areas on the teeth can be easily highlighted with the eraser.