Use of dyes as a colorant has the advantage of penetrating the fiber, resulting in a somewhat more flexible and translucent sheet than paper colored with pigment. Because dyes to not interfere with hydrogen bonding, the resulting sheet is also stronger. However, dyed paper will generally fade over time as the chemical elements continue to react to sunlight and oxygen. Dyes require a mordant to set the color. Natural dyes can be made by macerating plant materials, soaking overnight, boiling, straining, then adding fiber to the colored liquid.
Dyes are also available commercially.
Pigments are the colorant of choice for most papermakers. Synthetic pigments have similar properties. Professional pigments available from papermaking suppliers come with suggested formulas for the amount of pigment and retention agent to use based on the quantity of dry pulp. When properly pigmented, the pulp should be colored, and the water should remain clear. A little pulp placed on a blotter should not bleed color into the blotter.