Acid Metal Etching Science Projects
Datetime:2013-10-09 Hits:
In acid metal etching, an image or pattern is obtained by coating part of a metal plate with a protective “ground” before submerging the plate in acid. Where exposed, the acid dissolves the metal slowly while the ground-covered portion is left unaffected. This produces a pattern. There are many variables in the process that can be developed into unique science fair projects.
Choosing a Metal
Although almost any metal can be etched by acid, the most commonly used are copper and zinc. Plates are commercially available through art supply stores. Although zinc is cheaper, it can produce pitting in the etching process that may make quantifying results difficult. In contrast, copper yields a much smoother etched line. Consider varying the metals (more than just zinc and copper) used to explore the reactivity of different metals with the same acid.
Selecting Grounds
Traditional wax-like “grounds” are difficult to work with. A number of other substances can be used repel the acid: fingernail polish, acrylic paint and varnish can provide a wealth of possible project focuses. How thick must the layer be, is there a time limit on using them, does brand matter—these are all interesting starting places for a science fair project.
Etching With Acids
To do the etching, metal plates are submerged in an acid bath, traditionally filled with nitric acid, although other acids can work. This part of the process should be done in a chemistry lab with a functioning fume hood since the reaction produces toxic fumes. Your teacher can order one (or several) acids, set up, supervise and dispose of acids for you. Since the etching is a chemical reaction, different metals with different acids will produce different results. Keep in mind that the concentration of the acid, as well as the length of time the plates remain in the bath, will alter the outcome.
Non-toxic Alternatives to Acids
Alternatives to using acid in etching have been developed to avoid acid's toxicity, although otherwise the procedure is exactly the same. Ferric chloride is commonly used instead of acids, and may provide an interesting comparison to acids in your project. If you choose to use it, be aware that ferric chloride, although not as bad as nitric acid, is still toxic and should be handled by your chemistry teacher.
Using Additives
The artist Friedhard Kiekeben has experimented with improving etching effects by introducing citric acid to his ferric chloride bath. Experimenting with additives may produce some interesting results. Selection of additives should be done together with your chemistry teacher, as adding some things to acids or ferric chloride may produce dangerous products.
Safety
Working with acids is dangerous. Although applying grounds may be done at home in a well-ventilated area, do not do the actual etching at home. Acid work should be done in a chemistry lab with a qualified professional supervising. The mixing and pouring of acid should be done by a qualified adult. Always be extremely careful and wear protective clothing, gloves and chemical goggles.
