Grandad sketch ?WIP?

Here's a new drawing I'm in the middle of. Well, I say the middle of. Its more that point where I walk away from it and try to forget what I was doing. When I come back to it tomorrow evening, I'll either think, "Oh Goodness! That's not even nearly done" or I'll say, "Hey. That's better than I remember it!"

At the moment I'm stuck because I can't see where to add a line that won't mess it all up and I've got a bit fussy with it. He's got white hair, which is kind of hard to draw, so I've bottled it a bit and ignored the top of his head entirely

Coward

Well, off to sleep. When the light is better I might update the photo, failing that, the drawing itself.

Would welcome your thoughts. I've left the original downloadable so you can get a proper view of it. This was going to be a present for my father (his birthday this weekend, and that's his dad in the pic) but I'm not so sure now I'm looking at the piece.

Ah well, off to see the pillow.