Searle's Process

I haven't identified what this picture was made for but I thought it interesting as it gives an insight into Searle's colouring process. There are three parts - the line drawing on art board, a xeroxed overlay and the coloured back-board with watercolour over light blue pencilling. He wouldn't always work like this and it appears to be a late period drawing so colour separations were no longer needed. Perhaps he was getting two pictures out of it (and two payments?). Let me know your thoughts in the comments section below.