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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
.
EQUIPMENT FOR GALV-ETCH 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 (TOP) 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 5, 10 and 20 amps costing from about 125 - 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 on page 23, which can be made up by an electrician. The use of 6 volt batteries in motor cycles is becoming rare, 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)..(TOP)
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 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)
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. 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). 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. Otherwise, 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 the galv-on semi-dry process described later you will need thick blotting paper and good quality felt 10 mm thick. 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 flat trays you will need metal grids which are simple to make up out of wire or you can adapt off-the-shelf stainless steel grids by plating them with copper or zinc. For etching in a vertical tank you will need to make up a metal cradle to hold the plate to be etched (described later).
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 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 strips silver-soldered to frame, bent to allow grid to be lowered to touch surface of electrolyte. A 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. |
