Copper Sulphate for Zinc and Aluminium
1 litre of warm water
100 gms of copper sulphate
100 gms of sodium chloride (salt)
Add copper sulphate and salt to water and stir till dissolved. (Always add chemical to water never the other way round.) For aluminium double the amount of salt to copper sulphate.
- When etching, a loose coppery sediment floats off. For use with hard ground, feather this away. When using for aquatint rock the tray gently to dislodge – this is important as a build up will stop the aquatint process happening properly.
- Time guideline. For a light etch 2 or 3 minutes, a deep etch 7 – 12. For aquatints a 2 minute etch followed by a 3 minute etch will get me a Solid black. Temperature and age of mordant will affect these times.
- When decanting the solution back into the storage bottle sieve it through mull to take out any solids. Depending on how you like to dispose of these things, they can be dried, stored and taken to the chemical dept of your local recycling station.
- Aluminium has a film over the metal which will prevent it from etching properly if not removed. Use a fine gage steel wool or Vim (an abrasive household cleaner) to remove film, polish and continue.
- One bonus with aluminium is it will give a light to medium aquatint when simply placed in the copper sulphate solution.