Degrease the metal plate to ensure you are starting with a clean surface. Grease on the plate will deter the adhesion of an aqueous solution, which is comparable to how oil repels water.
Dampen the plate with a rag soaked in straight white vinegar to begin the design and application of the etching. The final etching design will reflect the natural tendencies of the vinegar as it begins to rust the plate at this point. After applying the vinegar applied but before it appears dry, creative manipulation of the etching can be achieved through the use of materials like plastic bags or sponges, allowing for artistic touches in the overall design.
Remove the tarnish obtained from the plain vinegar with a clean rag and then set the metal plate aside. Pour the hydrogen peroxide into a large jar and add the vinegar and salt. If using the animal blood, add this to the solution as well. Mix vigorously until the solution becomes homogenized. Using a small brush, apply the mixture in a thin layer over the total area of the plate. The design will begin to appear in the areas that have been covered.
Leave the solution on for up to one hour; the time the solution remains on the plate determines the depth of the etch. Dab the metal plate with a clean rag, but avoid wiping the plate, as this will create smears in the design. Using a stationary press, put the plate to paper. The rust will transfer to the paper, revealing the design as a print.