Applying Gesso to the Vellum: My desk set up for the application of gesso. The places that have already been gessoed on the manuscript are plainly visible as being pink. At top is my practice strip of vellum. On the right side, the mortar contains freshly reconstituted gesso with the application brush. Medieval scribes typically used a quill pen cut with a long tip and slit for flexibility to apply gesso instead. There is also a glass of distilled water for adjusting the gesso's fluidity as the moisture evaporated from the batch—many scribes' gilding sessions have been ruined by not accounting for the evaporation of water or separation of glue from filler as the gesso sits out.