It starts with a rough outline to get the size of the head and the features in the right place.
With the outline done, as always, I start with the eyes. I'm drawing on a flat white cartridge paper, there's no texture to the paper, and I'm using a mechanical pencil with a HB lead.
The reference image I'm using for the portrait was taken in bright sunshine, and Carl's smiling, so the light and his facial expression makes his eyes seem smaller than if his face was relaxed and in softer light. This bright lighting is going to be a challenge!
Even with the eyes smaller I still need to capture the intensity in his facial expression, so I start right in the middle of the eye. The pupil is going to be the darkest part, but it needs a spot of reflection, a highlight, otherwise the eyes will look flat.
With the darkest part down, I start building up the tonal detail around the eye. The nose guard of the helmet is casting a shadow over the other eye, and blocking out any highlights within the iris and pupil, so this is going to be tricky not to make the eye look flat and lifeless.
I'm using the pencil to make soft cross-hatching marks that blend into each other and I'm building up layers of darker pencil to suggest the 3-dimensional form of the eyes. As I work, I sketch on both eyes, building up each a little at a time so that the tonal qualities work together.
The bright sunlight is on the right side of the face as we're looking at it, and at this stage I'm think of leaving the paper completely white to show the brightness.
So I'm just slowly mapping the tonal changes on the face as it transitions from shade to sunlight. I'm not worried about the range of tonal depth, just mapping the shapes out loosely.
I'm not decided yet, but I'm thinking of making the details around the edge of the face a little out of focus, or more sketchy, so there's more emphasis on the main part of the face.
But it's early days yet, I still have an enormous amount of work to do, and the feel of the portrait may change as work progresses. It's certainly going to be a challenge though!