Use either a scrapbook page or prepare a paper of appropriate thickness. You may also adhere two papers together to create your single scrapbook page. Fit on gloves if you wish to avoid walnut ink staining your hands; the water-soluble solution is easy to remove with warm water.
Mix the walnut ink. If the package you have is pre-mixed, proceed to the next step. For walnut crystals, place a couple crystals in your designated mixing container. Mix them with warm water in the container in accordance to the directions on the walnut crystals package. The more water added, the more diluted the solution will become. Stir with your stirring stick until the crystals are dissolved and the solution is an even, solid color.
Dip the paintbrush tip into the walnut ink solution and apply a light first layer to your liking. The paper will likely warp; thicker scrap paper or two sheets adhered together will warp less. Wait for the paper to completely dry.
Repeat the previous step if you would like a darker shade and wait for it to completely dry. Use a paper towel to sop up too much walnut ink. Try flicking or spilling splotches walnut ink onto the paper for an authentic looking spotting effect of antique documents. Use a spray bottle for a similar effect.