This information is reprinted from the Beginner Topics column of Hand Papermaking Newsletter #63 (July, 2003).
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Color and Pigments
Summer is such a colorful time of year. I am reminded of being in Walter Ruprecht’s wonderful facility outside of Harare, Zimbabwe, and seeing a rainbow of papers, but no pigments. He made all of his wide variety of colored papers from bright cotton clothing.
This is certainly one method of making colored paper. Whatever fiber color you begin with will remain approximately the same in the finished paper. This approach assumes, however, that you have access to conventional production equipment.
The recycling of papers will also generate color. If you are a “blender” papermaker you can add brightly colored tissue paper which bleeds very quickly, producing vibrant--though fugitive--colors.
But for those of you papermakers who want to understand more about “serious” color, and find the whole subject very mysterious, let’s take a closer look. Papermaking color comes in two primary (no pun intended) types: pigment and dye. The simplest way to understand the difference is to imagine the paper fiber being like a straw. When given a dye, it sucks it up and changes the fiber to the given color. On the other hand, pigments just sit rock-like next to the fiber; the human eye sees the color, but the color is beside--not in--the fiber.
This difference has an impact upon permanence as well. Paper is hygroscopic: it “breathes” in moisture from the environment. Our environmental moisture is charged with chemicals of its own. When these chemicals in the air reach dyed fiber, there is a stronger reaction, or change, than if the moisture contacts a lump of pigment. Therefore, papers colored with pigments are more permanent than papers colored with dye.
Pigments are often dispersed in liquids. These dispersing agents come primarily in two types: water and oil. For example, we have watercolor paints and oil paints. Hand papermakers sometimes use aqueous dispersed pigments available from special suppliers. Artist’s colors that are water based can also be used by simply mixing the tube color with water and adding it to the pulp. Dry pigments are easily purchased, and these need to be ground with water and sieved through fine mesh before using.
Once the pigment to be used is ready, the second major issue comes into play. Paper pulp has a negative chemical charge and so does the pigment. This means they do not want to mix. Papermakers need to add a chemical agent to make the pigment bond to the pulp. This substance is called retention agent. It has a positive charge and will help to hold the pigment to the fiber. It is available from hand papermaking suppliers.
Small amounts of retention agent added to the pulp cause the pigment to hold to the fiber, make the fiber a more intense color, and allow the surrounding water to run clear. The proportion of retention agent to fiber varies greatly. Red and yellow are the hardest colors to retain, while browns and blues are easier. Proportion is a matter of experimentation, but it is worth the effort because the end result is a beautiful palette of colors to use confidently in your work.
I encourage you to experiment with a variety of pigments and create a summer rainbow of color. I will continue this introduction to color by discussing dyes in the next newsletter. So don’t let your subscription lapse!
Copyright 2003 Hand Papermaking, Inc.