Equipment for Galv-etch and Galv-On electrolytic etching methods; power supplies: control box; diagrams of equipment setup for tray/grid process. Extracts from GREEN PRINTS by Cedric Green published by Ecotech Design, Sheffield, UK. - a handbook on new methods for non-toxic intaglio etching and metal plate printmaking, featuring the technique of Galv-Etch, a modern development of the 19th century electrolytic techniques of Electro-Etching and Galvanography, and introducing Fractint and other alternative methods for avoiding the use of solvents and chemicals harmful to health and to the environment .

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EQUIPMENT FOR GALV-ETCH

what to buy

This guide assumes that someone using galv-etch for the first time will be making medium size prints - from plates up to about 40 cms on the longest side, and will be wanting to etch needled grounded or tinted plates (see fractint later)or etch areas of open bite. Larger plates can obviously be made, and the methods and equipment recommended will be described later. To start off you may not want to invest a lot of money and can make use of existing equipment like acid etching trays. In particular the galv-on semi-dry process described later can be done with the simplest equipment of all. Nearly all the equipment needed can be bought from DIY stores, electrical and electronic suppliers, motor spares suppliers or hardware shops. Some readers may not be printmakers at all and will want to etch other objects like badges, name plates, dials, knife blades etc. I hope these pages will be helpful to them too, and I would only warn that if very small areas are to be etched, the voltage and current required are small and the resists required must be very robust (

power supplies

The most important piece of equipment is a direct current power supply unit with switched voltage outputs and voltage and amperage displays. The most satisfactory and versatile type is a DC regulated laboratory power supply. In Europe, Velleman Instruments (website address: www.velleman.be) are distributors of a range of power supplies of this type. There are models which can be switched from 0 volts upward and with maximum outputs of 3, 5, 10 and 20 amps costing from about 75 - 300 Euros. To begin without spending a lot of money, you can use a 6 volt car and motorcycle battery charger, with built-in ammeter, and fused short circuit and overload protection. With a battery charger it is necessary to have a control box as shown and described below, which can be made up by an electrician. The use of 6 volt batteries in motor cycles is becoming rarer, but heavy duty 6/12/24 volt chargers can still be found capable of up to 20 amps. but voltages higher than 6 volts should never be used. For etching very small areas at low voltage, you can use a direct current mains adapter which can be switched down to 1.5 volts. Similarly, for small plates I have successfully used a small array of photovoltaic solar cells producing between 4 and 0.5 volts in bright sun. The control box for the last two options only needs a sensitive voltage and amperage display. There are other sources of direct current that can be used, like rechargeable batteries, but never use more than 6 volts, and then only with a control box to adjust and display the voltage by introducing a fixed and/or variable resistance. An accurate display of amperage is very useful also, which is used for calibrating the system to calculate the time required to etch (see times and tests)..

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3amp

Three Laboratory power supplies from Velleman illustrated below. (The velleman website lists European retailers of this equipment)

In each country there are different local manufacturers of power supplies. The least expensive have usually analogue displays of voltage and amperage

 

 

- switched 0 - 15 volts and 3 amps which weighs 2.5 kilogrammes (approx. 75 Euros). This is the one I use most for plates up to 16 cm x 25 cm

- switched 0 - 18 volts and 5 amps (approx. 125 Euros).

 

- switched 0 - 30 volts and up to 10 amps, with digital displays (approx. 220 Euros ) A larger model is available with output up to 20 amps.

A purpose made control box is not necessary with these types of power supplies.

12 amp 6/12 volt battery charger unit with switches and built-in ammeter, and on the left - a purpose made control unit with halogen lamp, variable resistance, ammeter and voltmeter (details on page 23) to use with any direct current power supply other than ones shown above.
Robust type of battery charger for 6/12/24 volts capable of up to 20 amps. For large plates with open bite or for galvanoplasty, or galv-on, this option used with the control box may be required when large amperages are demanded. But never use 24 volts or 12 volts.
Power supply for galv-etching small needled plates up to 300 sq. cms. - small DC mains adapter with a switched output of 1.5 volts and about 3 amps output at 1.5 volts. Shown next to control box, which can simply have voltage and amperage meters showing up to 3 volts and 3 amps.
Solar photovoltaic collector power supply, for small etched areas. For this and the mains adapter shown above the control box need not have a halogen lamp voltage reducer and the displays should be more sensitive and display only up to 3 volts and 3 amps.

The control box which is needed if you are using an unregulated supply (eg battery charger) or any power supply which is not switchable down to 1.5 volts. It can be made up easily by an electrician from inexpensive components - a 12 volt halogen lamp and holder, a 50 watt 5 ohm variable resistance, a switch, a voltmeter and an ammeter. The circuit diagram is shown below. (TOP)

 
Circuit diagram of control box above. Note that the voltmeter should be able to register the maximum output of the power supply when switched direct, and the ammeter in series only measures the current when the resistor and lamp are switched in. The wiring should be heavy duty enough for the maximum amperage of the power supply.  
Purpose made control box to use with 6 volt battery charger, battery or other direct current source like solar cells - model with voltmeter and ammeter. Note ventilating metal grille over halogen lamp
Back of control box. In the centre at the back is the knob for the 50 watt 5 ohm variable resistor and on the right the switch for output either through resistors and ammeter or direct to crocodile clips.

chemicals and materials

For working with copper plates you will need copper sulphate; for zinc plates, zinc sulphate and for steel plates, Ferrous Sulphate or Ammonium Ferrous Sulphate. The chemicals can be obtained from suppliers of industrial chemicals, and copper sulphate crystals may be obtainable from gardening shops where it may be sold to make up Bordeaux mixture, used to spray plants against mildew. But do not use readymade Bordeaux mixture which contains other ingredients. Make sure it is pure copper sulphate. The amount of chemical will depend on the size of tray or tank you want to fill.

In general, the electrolyte solutions, all the cathode plates, plate contacts, grids, etc. should be of the same metal as the plates with which you are working, so in the section below I will use the word 'metal' to avoid repetition and confusion. So for example if you are working with copper plates, you will use copper sulphate, and the cathode plate or grid will be of copper, and any other metal like solder, bolts or pop rivets must be varnished to protect them. Similarly, if you are using zinc, substitute the word 'zinc' for 'metal'. Never mix metals or galv-etch one metal in the sulphate of another (see the section on ''chemistry of Bordeaux etch' for an explanation).

Do not be tempted to use Salt solution ( or brine) as an electrolyte as has been suggested on various websites, as the results of the elctrolytic action with brine are to generate chlorine gas, hydrogen gas, to turn the electrolyte into caustic soda, and with different metals as the plate or cathode, to be left with a toxic brew of different chemicals (see links for further information) .

For biting small plates with needled lines or tint, a traditional open tray can be used, provided it is deep enough. I use photographic developing trays, and for larger plates, plastic storage trays with lids. The type of tray used does not need to be acid resistant, but must not be metal. For etching in a flat tray you will need a metal grid of the same metal as the plate. These are simple to make up out of thick electrical copper wire or strips of offcut roofing copper. (illustrated in 'preparation') For zinc plates galvanised steel fencing wire can be used to make the grid. Or alternatively you can use off-the-shelf stainless steel grids prepared by plating them with copper. (see section on plating a grid ).

Later on when you become more ambitious and if you plan to do large areas of open bite and deep etch, or galvanoplasty, you may need a deep tank in which to hang plates on a cradle.

For the galv-on semi-dry process described later you will need thick blotting paper and good quality washed felt of different thicknesses. You will also need an assortment of crocodile clips, heavy duty insulated wire and strips of copper, zinc or iron, depending on what metal you are using.

For etching in a vertical tank you will need to make up a metal cradle to hold the plate to be etched vertical (described later).

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Expanded diagram of standard all- purpose equipment for galv-etch, (wet process) Note: for zinc plates substitute the word zinc for copper in the key below. For steel plates the electrolyte is ammonium ferrous sulphate.

Key to diagram above

[1] Deep plastic tray with electrolyte (copper sulphate 1:4)

[2] Copper "backplate contact" - flat copper plate with copper strap soldered to back, varnished except upper face for contact with back of plate.

[3] Copper plate prepared for galv-etching, with back unvarnished to allow electrical contact on backplate.

[4] Grid to form cathode; heavy copper wires or strips silver-soldered to frame, bent to allow grid to be lowered to touch surface of electrolyte. A plated stainless steel grid can be used (only for cathode).

[5] Power supply - see above for different options

[6] Control box with 5 ohm, 100 watt variable resistance (optional), 12 volt 50 watt halogen light bulb, and two-way switch to pass current either direct to crocodile clip, or through bulb and variable resistance first. Box must be wired in series on the positive lead. An ammeter that will measure up to the maximum output of the battery charger wired in series, and voltmeter wired in parallel are very useful optional extras. (see above for details)

[7] Mains switched socket with optional time switch (countdown).

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