Laboratory: Etching Zinc Plates for Embossing and Printing

Purpose: To learn the procedure for preparing a zinc plate to be etched. To consider the factors that affect the etching of a zinc plate. In pairs, to design and execute an experiment to examine one of these factors. As a class to share experimental results and determine optimal conditions for etching a zinc plate. To use optimal conditions to etch the zinc plate to be used for the embossed and printed final image.

See the instructions for printing with the etched zinc plate.

This experiment was largely designed by Carolyn E. Fitz.

Each of the images below can be enlarged by clicking on the image of interest.

1. Obtain three pieces of zinc plate (2 smaller, 1 larger). Peel-off plastic coat from plate. The smaller plates are for experiments with the variable factors; the large plate is for the final image.
2. Bevel the edges of the plates with a triangular file.
3a. Clean off ZnO coating with putz-pomade (abrasive).
3b. The towel will get quite dirty looking...
3c. ...and the plate will become shinier...
3d. ...and shinier!
4. Holding plate at edges, clean plate with isopropyl alcohol.

5a. Lay clean plate on piece of paper toweling in hood.


With a brush, apply an even coat of ground onto your clean zinc plate in hood (try to avoid double thickness, but plate must be coated).


Allow coated plate to stand in hood until ground is hard (dry).

5b. Close-up.

6. Allow coated plate to stand in hood until ground is hard (dry).

Keep the beaker of the ground solution covered to prevent evaporation!
7a. Remove coated plate from hood and using an etching needle selectively remove ground to create your design on the plate.
7b. Another view of working with the etching needle.
7c. The image is emerging.
8a. Immerse plate into etching bath (4M nitric acid) and continue to etch until desired depth of bite is achieved. (There will be some suggestions for experimental options to explore at this point. They will be discussed during the lab period.) While the plate is being etched, NO gas (colorless) and/or NO2 gas (red-brown) will be produced on the surface of the plate. The bubbles should be brushed away with a small brush. Do not let bubbles collect on the surface of the plate.
8b. While the plate is being etched, NO gas (colorless) and/or NO2 gas (red-brown) will be produced on the surface of the plate.
8c. The bubbles should be brushed away with a small brush. Do not let bubbles collect on the surface of the plate.

9.When the zinc plate is etched (bitten back) to your satisfaction, remove it from the acid bath and rinse it with tap water to stop the chemical reaction. Pat the clean plate dry with paper toweling.

In the hood, remove the ground from the etched plate using mineral spirits and paper toweling. Be sure the plate is completely clean. Discard waste towels in receptacle in hood. Important. Do this work in the hood.

Make a final rinse of the etched plate with iIsopropyl alcohol, holding only on the edges. Wipe dry with paper toweling.

10. Store prepared plate(s) in plastic bag (with label) until the next lab period.

  

John Bordley, 2002