The original of the girl with the pearls is by Henry Tonks. He taught at the Slade over 100 years ago. I remember being struck by his forensic studies of facially disfigured soldiers from WW1. My grandfather served in the Royal Medical Corps, so Tonks' drawings held a personal resonance. Tonks used red chalk and wash on white paper. His treatment of tone is amazingly sensitive. I have attempted this crude copy in chalk and charcoal on coloured paper.
The 1897 original of Ursula Tyrwhitt's profile is by Augustus John. This is also in red chalk, but with a grace of line and a sureness of pressure that are quite amazing. I used HB and 6B pencils to try and echo the delicacy of outline and the softness of tones. I had to stand and squinny up-close to the picture, holding my sketch-book so my legs and left hand went numb with the effort. But truthfully, it's a poor excuse: even if I'd been comfortable I would still have fallen short. John's draughtsmanship is stunning, and attempting a copy made me painfully aware of that.