Acid Etching
Etching involves use of dilute nitric acid, Dutch mordant (hydrochloric acid plus potassium chlorate) or ferric chloride to etch the zinc or copper (respectively) metal plate. Unetched parts of the plate are protected with resists such as stop-out varnishes containing ethyl alcohol, grounds containing asphaltum or gilsonite and mineral spirits, rubber cement, and rosin or spray paints for aquatinting. Sometimes, soft grounds contain more toxic solvents.
Hazards
- 1,1,1- trichloroethane found in some soft grounds is an inhalation hazard under normal conditions but may cause fatalities at very high concentrations.
- See Acids section for the hazards of acids. In particular, nitric acid etching releases nitrogen dioxide, which can be a respiratory irritant, and has poor odor warning properties.
- Concentrated nitric acid is a strong oxidizing agent and can react with many other chemicals, especially solvents or other organic compounds, to cause a fire.
- Mixing hydrochloric acid with potassium chlorate to make Dutch mordant produces chlorine gas. Potassium chlorate can react explosively with organic compounds, sulfur compounds, sulfuric acid or even dirt or clothing. On heating, it can violently decompose to oxygen and potassium chloride. Storage and use require special precautions especially when mixing.
- Rosin dust (and asphaltum dust which is also sometimes used) is combustible. Sparks or static electricity have caused explosions in enclosed rosin and aquatint boxes. Rosin dust may also cause asthma and dermatitis in some individuals.
- Inhalation of solvents and pigments can result from the use of aerosol spray paints.
Precautions
- Obtain the SDS for all materials used.
- See Solvents and Acids sections for specific precautions.
- Use Dutch mordant with extreme caution. A safer substitute for etching copper plates is ferric chloride (iron perchloride). This forms acidic solutions so should be handled accordingly, but does not have the dangers of handling concentrated acids. Ferric chloride solution might cause minor skin irritation from prolonged contact.
- Application of grounds or stopouts should be done with local exhaust ventilation, (e.g. slot or enclosed hood).
- Acid etching should be done with local exhaust ventilation. See the section on precautions for Acids for more information.
Drypoint, Mezzotint and Engraving
Other Techniques Drypoint, mezzotint and engraving use sharp tools to incise lines in metal plates.
Hazards
- One major hazard associated with these types of processes involves accidents with sharp tools.
Precautions
- Keep tools sharp, store them safely and always cut away from yourself.
- When possible, clamp down plates to avoid slippage.
- Minimize the chance of hand fatigue by choosing tools with wide handles, avoiding tight grips.
Printing and Cleanup
Intaglio inks contain pigments, treated linseed oil and modifiers. Printing involves placing the ink on the inking slab, inking the plate by hand, and then printing. Cleanup of inking slab, press bed, and cleaning the plate is done with a variety of solvents including mineral spirits, alcohol, lithotine, turpentine, etc.
Hazards
- Preparing your own inks from dry pigments can involve a potential inhalation hazard. See Pigments section for the hazards of pigments.
- See Solvents section for the hazards of solvents.
- Lithotine, turpentine, or oil-soaked rags can be a spontaneous combustion hazard if improperly stored.
Precautions
- See Pigments and Solvents sections for the specific precautions for pigments and solvents.
- Ensure local ventilation is utilized. Relief and Other Printing Processes Other printing processes include relief printing, collagraphs, monoprints, and plastic prints.
