The depth of the lines produced by electro-etching is proportional to the etching time and the amount of electrical current flowing through the electrolyte solution (depth ∝ current x time).
Consequently by increasing the current the etching time can be decreased. It is important to understand that the amount of current which can flow depends on how much bare metal is available for etching. This bare metal is a result of the lines made in the ground when the image was drawn onto the plate with a needle or open areas of metal made to generate micro-dots. (see below micro-dot)
The electrical current is directly proportional to the voltage set on the power supply: increasing the voltage increases the current. Voltage is measured in volts and current is measured in amperes (amps). The amount of current flowing is related to the amount of bare metal it is etching as described above. If the voltage is set too high then unwanted effects may arise. Until experienced is gained with a particular electro-etching system it is better to use slower rather than faster etching.
Electro-etching lines and electrotint on copper plate
With any of the metals and concentrations shown on the previous section, I usually use a very low voltage of 0.5 volts. For the small plates shown in this article, the corresponding current is around 0.4 amps. With this voltage and after 15 minutes of electrolysis, we will have a printable line. A plate will need to be etched up to 60 minutes to get deeper lines.
I recommend you make step tests of single and crossed lines at intervals of 15 minutes up to a total of 120 minutes so you can discover the times needed to reach the intensity of etched lines for your work.
You can also etch with a voltage of 1.0 volt. But remember it is better to keep to low voltages (currents): to use higher values may cause the varnish/resist to become detached from the plate.
WARNING: If a voltage as high as 10 volts is used for etching, the conductive solution generates hydrogen at the cathode and oxygen at the anode. It is possible for the hydrogen and oxygen gases to combine and explode on contact with a single spark, such as that which may be caused by a switch. To avoid this simply etch with low voltages.
Some practitioners recommend not going above 6 volts. My first experience with electro-etching was at a very low voltage – 0.5 volts – and even with this I could etch lines of different sizes and depths, and diverse tonal effects. I have also experimented with 1 and 2 volts, but the results have not been so remarkable as to encourage further testing with higher voltages. My work has always been done using a range of between 0.5 and 1 volts, and I have not needed to increase voltage to achieve new or different effects.
Before starting to etching remember that you are going to be working with a low voltage.