Princeton Quill Brush - #8Princeton Quill Brush #8 (Synthetic Squirrel) Princeton has done it again. A few years ago, Princeton gave artists a synthetic version of sable that was almost the equal of Kolinsky and is still the standard for performance for its rivals. When they set out to create a synthetic version of squirrel they developed a brush that may actually out perform the natural version. Neptune is their thirstiest brush ever delivering oceans of colour to the sheet.