SAFETY PRECAUTIONS

The list of basic precautions listed below are mostly ones that an experienced printmaker who uses electrical equipment of any kind will know, but as this is all about safe printmaking, they are repeated here together with some that are specific to galv-etch using the equipment I have described.

A special warning is added here about using salt solution (brine) as an electrolyte because a number of books and recent websites have suggested using salt or adding salt to electrolytes. Using brine as an electrolyte generates chlorine gas, hydrogen gas, and produces caustic soda. Different toxic chemicals are produced when etching metals like zinc, aluminium, and steel. Free copper deposit produced by etching zinc plates in saline sulphate etch forms a 'zinc copper couple' which generates a current and produces chlorine, hydrogen and caustic soda. Free chlorine and hydrogen gas in a confined space like a covered etching tray can form an explosive mixture. If the chlorine gas is not channelled and collected, but mixes freely with the caustic soda, then sodium chlorate is produced . Sodium chlorate is a very toxic chemical banned since 2008 in the European Union where it was used as a powerful weed killer. (see the Appendix C for further information about the processes of electrolysis of brine) .

  1. The area where you do galv-etch should be free of solvent fumes of any kind (as the whole working space should be). Make sure all your electrical connections from battery charger to the mains are correctly made and that the whole system is protected by a mains switch which is easily accessible. If you are using a time switch on the mains input, it should be switched.

  2. On the low voltage direct current output from the power supply (battery charger) you will usually find a pair of large crocodile clips, the positive on a red wire, negative on a black wire. While the system is not in use clip these both to an insulating strip of plastic or card so that they cannot touch accidentally. If you make any new leads always use wiring of the same type and weight, and make all joints mechanically with screwed junctions, not with soldered joints.

  3. When you are preparing to start a galv-etch, put the plate and cradle or connecting bar into the electrolyte and make all the connections before switching on. Do not make or unclip any connection while the current is flowing or you may create a spark - if you have to stop the etch quickly, turn off at the mains switch.

  4. Take great care using a flat tray with a cathode in the form of a grid of wires, and do not try to control the current by lowering the grid into the electrolyte. If you are using a vertical tank and lowering the cathode into the electrolyte to control the resistance, start off with it just touching the surface and clipped to the side, switch on and then unclip it, lowering it slowly while watching the ammeter, and re-clip it when the right level is reached. To avoid an uneven depth of etch, check that the immersed part of the cathode is opposite the centre of the plate.

  5. If the power supply is overloaded, switch off quickly and first check that you don't have a short circuit somewhere - a plate bar strap touching a grid support for instance. If not, use another method like a vertical tank, a diluted electrolyte, or use a different power supply like a rechargeable battery or solar cell array, or include a resistance like a 12 volt lamp in series in the circuit, or a control box as (shown elsewhere). Note that adding a resistance reduces the voltage and produces a more gentle galv-etch which takes much longer.

  6. If you use a lead acid rechargeable battery (12 volt car or 6 volt motor cycle battery) you must have very heavy duty connecting wires - I recommend car jump leads to be on the safe side. Wire a mains switch into the positive (red) lead. Make all the connections with the crocodile clips first, then switch on, and keep an eye on the progress of the etch. Plating or galvanoplasty puts a much heavier load on the power supply, partly because the cathode - this time the plate on which you will be depositing metal (-ve) - will probably have a large conducting surface, and the anode (+ve) must be solid and not a grid.

  7. If the rate of etch seems too fast or vigorous, include a resistance like a 12 volt halogen lamp in series in the circuit. Mount the lamp in its socket with a two-way switch to cut it out if you don't need it. I have made a little control box with a 12 volt 50 watt lamp, a 2-way switch, and a 50 watt, 5 ohm variable resistance, wired in series on the positive lead from the power supply, which can be instantly switched in if the ammeter on the power supply indicates an overload, and then used to regulate the voltage (shown elswhere). Note that this resistance in series reduces the voltage and the amperage, and in consequence a longer time is required for the galv-etch, which may be necessary if you are using traditional soft ground or producing textures by pressing oily materials onto a bare plate.

  8. At any time that your hands might be in contact with the electrolyte, wear thin waterproof gloves because the sulphate solutions are slightly acidic, and in particular with zinc sulphate, take care to avoid any contact with skin or eyes, and keep all the solutions out of the reach of children Store it in a safe place, well labelled to avoid anyone having an accident or drinking it, as it is a clear liquid. No special precautions are required for copper sulphate, except perhaps wearing gloves to protect the skin from drying out and staining blue.

  9. Before lifting a grid cathode or the etched plate out of the galv-etch tray, make sure the current is off - cut by the timeswitch or off at the mains. If using a battery charger or mains rectified power supply, when you have finished work, switch off the mains supply to the unit. If you are using a battery, remove the leads from the terminals. (TOP).

Details of 2 of "Nine Variations on a back" - galv-etched and fractinted zinc plates

 

 



May 17, 2015