Etching the Zinc and Copper Plate
Created | Updated Oct 14, 2002
AN INTRODUCTION TO ETCHING
Aside from relief and engraving, etching is one of the oldest printmaking techniques. To create an etching, an artist first bevels the edges of a zinc or copper plate with a file or a scraper. After those edges are polished, the plate is briefly degreased with ammonia and whiting and washed with water. After the plate has completely dried, a variety of acid-resistant ground solutions can be applied to the plate.
CREATING AND APPLYING HARD GROUND
For linework and crosshatching, the plate should receive a hard ground. Hard grounds are available from most graphic and printmaking supply companies such as Rembrandt, Graphic Chemical and Ink, and Daniel Smith. However, the best hard ground mixes are made by hand. To make a quality hard ground, mix a high quality solvent (Lithotine or mineral spirits) with asphaltum. The mixture should be 1 part solvent to 1 part asphaltum. After the ground has been applied, it should be immediately placed on a hot plate until it begins lightly smoking. This is a vital step in the application of any hard ground, as too much smoking will lead to chipping of the hard ground, and lack of smoking will leave the ground unset, meaning that it may come off the plate at the lightest touch. After the hard ground begins smoking, the plate should be set aside for approximately 10 minutes, depending on atmospheric conditions.
LINEWORK
After the plate is completely dry and cool, it is ready to receive linework. Linework is applied with an etching needle, usually a sharpened piece of stainless steel in the shape of a pencil. Traditionally, etching lines are very orderly and uniformly spaced according the the desired value structure of the artwork as this makes for the longest editioning capability and the most easily read visual structure.
AQUATINT
Aquatint is the preferred method for creating tonal and gradated values. Several methods can be used to apply an aquatint. The zinc or copper plate should be prepared through degreasing with ammonia and whiting, and then thoroughly washed and dried. The most even tonal structure is achieved through a rosin-box aquatint. A rosin-box is a simple box that uses gravitational forces (by spinning the box) or air compression to circulate rosin molecules within that box. After the rosin particles are circulating in the box, the metal plate is placed in the rosin-box and checked periodically until it is approximately fifty percent covered with rosin. A spray-lacquer aquatint is second to a rosin-box aquatint in terms of tonal consistency. This form of aquatint is applied by spraying black enamel spray lacquer over a plate with the can in an upside down position. This method should also cover approximately 50 percent of the plate. The most inconsistent and cheapest aquatint method is ball-ground or bag aquatint, wherein rosin is sealed into a fabric of some sort and shaken over the plate. Different fabrics provide differing dispersions of rosin over the plate. The rosin should be broken up and placed inside the fabric, which should be wrapped around the rosin and tightly tied together. Specifically, the rosin is applied to the plate by shaking and hitting the bag against the wrist to force the rosin particles out of the bag and into the air. Regardless of the chosen method of aquatint, the plate is moved to a hot plate after the application of rosin. When the rosin becomes liquid in form and bonds to the plate, it is removed and set aside to cool.
ETCHING A PLATE IN AN ACID BATH
Different acids must be used on various metal types. Zinc plates require the use of a nitric acid bath almost exclusively, while copper plates can be etched with a traditional Dutch Mordant bath, or a phosphoric acid bath. While zinc is a harder metal than copper, it reacts faster to acid and thus etches more quickly. To contrast, it is not unusual for a copper plate to etch for 24 hours. Zinc baths are generally between 5, 10, or 15 parts water to 1 part acid. Copper baths are usually 10, 15, or 20 parts water to 1 part acid. The strength of the acid will affect how much the plate is etching in a given period of time. Whether the artist is etching linework or aquatint, he should etch the plate in stages, or steps. The longer a line is exposed to the acid, the deeper and wider that line will be. A step bite traditionally involves doing a first etch, applying hard ground where the lightest values are, doing a second etch, and et cetera. When all etching is done, the plate should be cleaned with a rag/toothbrush using mineral spirits or kerosene to remove the hard ground, and denatured alcohol to remove the aquatint rosin.
Aside from relief and engraving, etching is one of the oldest printmaking techniques. To create an etching, an artist first bevels the edges of a zinc or copper plate with a file or a scraper. After those edges are polished, the plate is briefly degreased with ammonia and whiting and washed with water. After the plate has completely dried, a variety of acid-resistant ground solutions can be applied to the plate.
CREATING AND APPLYING HARD GROUND
For linework and crosshatching, the plate should receive a hard ground. Hard grounds are available from most graphic and printmaking supply companies such as Rembrandt, Graphic Chemical and Ink, and Daniel Smith. However, the best hard ground mixes are made by hand. To make a quality hard ground, mix a high quality solvent (Lithotine or mineral spirits) with asphaltum. The mixture should be 1 part solvent to 1 part asphaltum. After the ground has been applied, it should be immediately placed on a hot plate until it begins lightly smoking. This is a vital step in the application of any hard ground, as too much smoking will lead to chipping of the hard ground, and lack of smoking will leave the ground unset, meaning that it may come off the plate at the lightest touch. After the hard ground begins smoking, the plate should be set aside for approximately 10 minutes, depending on atmospheric conditions.
LINEWORK
After the plate is completely dry and cool, it is ready to receive linework. Linework is applied with an etching needle, usually a sharpened piece of stainless steel in the shape of a pencil. Traditionally, etching lines are very orderly and uniformly spaced according the the desired value structure of the artwork as this makes for the longest editioning capability and the most easily read visual structure.
AQUATINT
Aquatint is the preferred method for creating tonal and gradated values. Several methods can be used to apply an aquatint. The zinc or copper plate should be prepared through degreasing with ammonia and whiting, and then thoroughly washed and dried. The most even tonal structure is achieved through a rosin-box aquatint. A rosin-box is a simple box that uses gravitational forces (by spinning the box) or air compression to circulate rosin molecules within that box. After the rosin particles are circulating in the box, the metal plate is placed in the rosin-box and checked periodically until it is approximately fifty percent covered with rosin. A spray-lacquer aquatint is second to a rosin-box aquatint in terms of tonal consistency. This form of aquatint is applied by spraying black enamel spray lacquer over a plate with the can in an upside down position. This method should also cover approximately 50 percent of the plate. The most inconsistent and cheapest aquatint method is ball-ground or bag aquatint, wherein rosin is sealed into a fabric of some sort and shaken over the plate. Different fabrics provide differing dispersions of rosin over the plate. The rosin should be broken up and placed inside the fabric, which should be wrapped around the rosin and tightly tied together. Specifically, the rosin is applied to the plate by shaking and hitting the bag against the wrist to force the rosin particles out of the bag and into the air. Regardless of the chosen method of aquatint, the plate is moved to a hot plate after the application of rosin. When the rosin becomes liquid in form and bonds to the plate, it is removed and set aside to cool.
ETCHING A PLATE IN AN ACID BATH
Different acids must be used on various metal types. Zinc plates require the use of a nitric acid bath almost exclusively, while copper plates can be etched with a traditional Dutch Mordant bath, or a phosphoric acid bath. While zinc is a harder metal than copper, it reacts faster to acid and thus etches more quickly. To contrast, it is not unusual for a copper plate to etch for 24 hours. Zinc baths are generally between 5, 10, or 15 parts water to 1 part acid. Copper baths are usually 10, 15, or 20 parts water to 1 part acid. The strength of the acid will affect how much the plate is etching in a given period of time. Whether the artist is etching linework or aquatint, he should etch the plate in stages, or steps. The longer a line is exposed to the acid, the deeper and wider that line will be. A step bite traditionally involves doing a first etch, applying hard ground where the lightest values are, doing a second etch, and et cetera. When all etching is done, the plate should be cleaned with a rag/toothbrush using mineral spirits or kerosene to remove the hard ground, and denatured alcohol to remove the aquatint rosin.
