Learning to blend is another one of those skills you need to master to become a good pencil portrait artist. Once you have a line drawing and once you have laid down the different values based on, for example, a five-value scale, bilder malen lassen nach vorlage

you can start blending the different value areas. To blend, you can use a pencil, a tortillon, a paper tissue, and even your fingers.

Here are a few blending guidelines:

Soft Edges

A soft edge occurs in a situation where an object surface gentle curves away from the light source. Such edges change values gradually and you should blend them accordingly.

Always blend parallel to the edges of the subject area. Follow the curves of, for example, a cheek. This allows you to blend into the edges and gives a more natural and rounded look.

Hard Edges

Hard edges occur where two surfaces touch or overlap. The edge looks more defined. Do not actually draw lines to depict such edges. Rather, create a hard edge laying down two different values next to each other.

Strictly speaking, there is no such thing as a line in nature. We become aware of lines only because of the contrasting values of two adjacent surfaces. And this is the way lines should be created in your drawings, i.e., by using contrast. Anything that has an actually drawn outline will look flat (i.e., planar) and will detract from the three-dimensional look of the subject.

Contrast

Contrast is a good thing. It gives life to your pencil portrait. Use your ingrained knowledge of the five-value scale to discern the correct values. An excellent trick to better perceive values is to look through squinted eyes. I also found it beneficial to draw in dusk-like lighting conditions.

Uneven Values

If you see uneven blending you can use your kneaded eraser to take off some of the darker spots and use your pencil to darken the lighter spots if needed.

Darkest Darks

If you need to create a really dark area you can build it up in layers. Start with a dark layer and spray it with workable fixative. Then put another layer on top. And, if necessary, you can repeat this process until the area is dark enough.

Kneaded Eraser

Your kneaded eraser is also a very useful  bild nachmalen lassen tool at this stage. You can use it to draw with into a penciled area. For example, the kneaded eraser is ideal to introduce highlights on noses and hair.

From Dark to Light

Always try to blend from dark to light. Blend from the shadows into the light. Remember, the highlights are the white of the paper while the cast shadows are the blackest black you can muster.