Etching is a common technique used by artists to prepare a printing plate and obtain prints. Various metals may be used to prepare printing plates, including copper, zinc, aluminium or steel. Steel is an inexpensive, durable metal that is ideal for large edition prints. Both mild steel and stainless steel are used in printing projects. The acids used to etch steel may include hydrochloric acid, ferric chloride, nitric acid or sulphuric acid. Sulphuric acid is a slower etching agent than nitric acid or ferric chloride.
Prepare the steel plate. Remove any dust, debris and impurities from its surface. Use paint thinner to remove grease.
Sand the steel plate. Start with a coarse-grit sandpaper. If you want to obtain a cleaner and a whiter background with fine details, sand the plate with a finer-grit sandpaper as well.
Remove any fingerprints from the surface of the plate using paint thinner.
Prepare a liquid solution of bitumen, using crude bitumen and paint thinner. Use 0.227kg. of crude bitumen in 4 cups of thinner and stir vigorously until the bitumen is melted. Apply the solution on both sides of the steel plate, especially the sanded side. This is the front of the plate.
Draw on the front of the steel plate using a metallic needle. Keep in mind that everything you draw will be reversed when you print on paper.
Prepare the sulphuric acid bath in a plastic container. Use one part sulphuric acid to five parts water. Don't stir the solution.
Immerse the steel plate in the container filled with sulphuric acid. Keep it in for 10 to 30 minutes.
Remove the plate from the acid bath and place it under running water for two to three minutes.
Wipe off the bitumen using a rag dipped in paint thinner. The plate is ready for the printing process.
Experiment etching with less toxic substances: try using copper sulphate mixed with salt to obtain a saline solution.
Sulphuric acid is extremely dangerous and shouldn't come in contact with your skin; don't inhale it. The working space should be well-ventilated. Use only sulphuric acid solutions with concentrations below 25%. Leave the room while the steel plate is in the acid bath. Don't use metallic containers for the sulphuric acid, because the solution will melt the container. When sanding the steel plate, don't forget the corners, because otherwise the printing press may cut off the corners of the paper due to the high pressure.