Aluminum plates are inscribed through a process that combines etching and engraving. The plates receive a coating of varnish, which constitutes a ground. Plates are then scratched with a sharp object to create an image. The varnish is selectively removed before placing the aluminum plate into an acidic chemical solution. Exposed areas of the plate react to the corrosive solution to produce the desired image.
A burin is a small tool designed specifically for engraving that consists of a sharp metal point. The point is used for etching designs onto metal plates. Because aluminum is a soft metal, a sharp needle will also work.
The etching chemical solution may consist of metal sulfates and an acid source, such as nitric acid. Newer techniques incorporate non-toxic ingredients, such as sodium chloride.
Use gloves and protective eyewear to avoid contact with caustic etching chemicals. Wear a mask to prevent inhalation of fumes. Use sodium carbonate to neutralize small spills of chemical solution. Place used etching solutions in a sealed container and dispose of properly.