Slack Jaw – Skull Illustration This pen and ink skull illustration called ‘Slack Jaw’ is simply another skull creation for no other reason than to draw. Who knows maybe after collecting some digital dust it will make an appearance somewhere. Created with pen and ink. Yeah kinda looks obvious. This skull was referenced from a skull photography book called ‘New Life’ by Pale Horse and available to buy from Illustrated Monthly for $14.99 as a digital download.