All,
Here is an example of 4 layer gum print on PVA sized Fabriano Artistico extra white paper. paper was sized with a 1:2Gamblin PVA/water mix and another layer of size was applied before last indanthrone blue layer was applied. Overall 4 layers were used with PBr25, carbon black (lamp black), PB60 and PO73. The last one is limited to the background. PBr 25 from Daniel SMith is an outstanding pigment that is perhaps to gum printing what burnt sienna is to oil paiting. It makes an outstanding combination when cooled with a second pass of indanthrone blue