The goal of a realistic drawing is to be as faithful to reality as it can. The drawing of hair has a certain degree of difficulty due to its complexity and wide variation and most beginners struggle with it.
1. Learn to see
For a hair to be drawn in a realistic way we must first train our eyes to perceive it properly. If we look close we will notice that although hair is made up of many individual strands, it does not appear that way. That is what our brain is telling us that hair is and that is what we know hair is. But what we see is another thing.
2. Create texture
While some hair strands are visible, most of the hair appears as an alternation of light and dark tones. Their size, intensity and direction give the illusion of hair. That is the foundation we start with. Details will come after we got the shape and the base tones right.
One important thing to remember is that hair is very complex and has a vast variation of appearances depending on person, hairdo, color and length.
3. Blend it
In realism, blending allows us to mask our pencil work and make the appearance softer. This comes in handy for a variety of textures from soft skin to rough clothing. With blending we can make the tonal transitions easier and refine the edges.
In a way, blending works like an airbrush. With the right technique and experience, blending can be a very powerful tool when aiming for realism. I always blend when I try to achieve a realist look to my drawing.
I advice you to blend the hair tones before you start adding the finer details, although sometimes I build multiple layers of blending and adding details and so on.
4. Insert highlights
After everything is in place and I am satisfied with my tones, I begin putting in the highlights. You can do this with either a kneaded eraser or with a crayon.
One thing to keep in mind is that the hair strings that do show, either lighter because they reflect the light or darker, are not of the same tone. For a better realistic effect try and vary the intensity of these visible hair strings.
5. Visible loose strands
The final touch are the loose hairs visible at the edge of the hair. If done right this small detail will enhance the appearance of the hair and make it seem real. I’ve seen lots of drawings of hair where due to the lack of loose hair strings the hair seemed like a solid rigid piece stuck to one’s head.
When drawing loose hair strands try and draw them in different directions. Begin by drawing them thicker at the base and thinner (barely visible) at the tip. Don’t overdo it as this can have devastating results that can compromise your entire work.