To start with, if you are galv-etching plates that have been grounded and needled, or fractinted, you can use a conventional flat etching tray. The tray needs to be quite deep, at least 6 cms. If you have not got a tray deep enough, you can use the kind of plastic food storage trays sold in supermarkets, because the galv-etch solutions are not corrosive, and don't need the special materials required for acids. Don't use metal trays though, even if enameled, in case of electrical short circuits.

Place the backplate contact into the tray with the strip bent up at the right position for the edge of the plate. Lower the plate into the solution onto the centre of the backplate contact. Place the grid onto the tray, with its wires just immersed in the electrolyte. At this stage make sure that the battery charger is switched off, either at the mains, or by a switch or timeswitch on its output.

Attach the positive (red) terminal of the battery charger to the plate strip or the backplate contact, and the negative (black) terminal to the grid or cathode. Check that you don't have any short circuits - leads, straps or crocodile clips touching. Then set the time switch, if you have one, and switch on, and watch the ammeter to check that the current is OK. If the needle goes off the scale, switch off, and use another method like a diluted electrolyte, or include a resistance in series in the circuit like a 12 volt lamp, or use a different power supply like a rechargeable battery or solar cell array.

Note that needled lines or tint can be etched by the Galv-on semi-dry method detailed later.

Deep-etch and open bite

A flat tray can be used for plating or open bite provided that you have some means of controlling the surge of current caused by the very low resistance of a plate with large areas of bare metal in the electrolyte. The control box shown in the diagram on in the section on equipment wired in series can be inexpensively made up from off-the-shelf components. Note that adding a resistance like this in series, has the effect of reducing the voltage over the anode and cathode (see section on times and tests). For plating, a grid (which becomes the anode) is not ideal as it is etched away and a solid plate can be attached to the underside of the grid.

If you wish to use a larger tank with the plate nearly vertical, the plate can be held on a metal cradle hooked over the edge of the tank, made from a broad strip of metal with the edge turned up on which to rest the plate with a bare area to make contact with an unvarnished area on the edge or back of the plate. All the metal bars, straps, clips, rivets etc. must be well varnished against being etched, just leaving the points of electrical contact with the plate bare. For the vertical tank make a cathode plate of metal by pop-riveting or bolting thin metal straps to each end, to hang over the edge of the etching bath. Alternatively a square plate with a long single strap can be used, which can be lowered into the tank to control the resistance. The cathode strip or square should be able to hang opposite the centre of the plate and be parallel to it. If it is not, the galv-etch may not be even in depth. To stop them being etched and prolong their life, seal all the metal crocodile clips, backs of plates, bars, straps etc. with ethanol+shellac varnish, or a strong stop-out varnish, leaving bare only those areas to be in direct contact with the plate

Etching a plate in a vertical tank

The alternative to a deep tray is a tank in which plates can be hung on a cradle. An alternative way of suspending a plate and simultaneously providing a contact and protecting the back is to cut a sheet of self-adhesive plastic sheet to the size of the plate and placing two thin strips of thin metal against the plate before sticking it on. The strips can be bent over to hang over the edge of the tank or to hang from a metal bar across the tank. Contact from the power supply can be made to the metal strips.

I use a type of plastic tank which can be bought off-the-shelf from a plumber's supplier or DIY shop, or for food storage from a supermarket. It requires a larger volume of electrolyte, but its greater width allows you to see the progress of the etch more easily and you can have more control over the distance between the plate and the cathode grid or plate. The cathode does not need to be the same area as the plate, but on average it should be opposite its centre and only slightly smaller. There is a tendency for lines or areas near the edges of a plate to be etched more deeply than the centre, and this can be counteracted by making the cathode plate smaller and therefore closer to the centre.

Large exposed areas of the plate will increase the load on the power supply and to keep the current within the limits of the battery charger's ammeter, the resistance can be controlled by simply lowering the cathode into the electrolyte slowly until the ammeter reading is at the level needed, and then clipping the cathode to the tank side with a large crocodile clip. I use a rigid plastic tank 48 x 30 x 30 cms deep, holding about 40 litres of electrolyte in which a plate 45 cm x 30 cm can be deep-etched safely. A larger width plate will fit diagonally in this size tank.

It is a good idea to have a tank with a tap about a quarter of the way up, in order occasionally to empty it without stirring up the sludge that eventually accumulates on the bottom. This can then be emptied and filtered and the clean solution returned to the refilled tank. If you don't have a tank with a tap, use a plastic tube as a siphon, and start the siphon going by holding it all under the electrolyte surface (with gloved hands) until it is filled with liquid. Then close both ends and take one end out and put it into the receptacle to store the electrolyte. Don't start the siphon by sucking the liquid up it. For storage I use plastic camping water storage jerry-cans, with taps.

There is not usually any need to protect the whole of the backs of plates because very little electrolytic action will take place "round the corner" as it were. The ions in the solution are most strongly attracted to the nearest surfaces, which are the facing sides of the anode and cathode plates. This also makes it easier to make an electrical contact with the back of the plate, avoiding the need for crocodile clips and possible marks on the surface.

Detail of "Nine Variations on a back" - lines drawn in an ink ground, galv-etched and then fractinted, and galv-etched in 6 steps, progressively stopped with ethanol/shellac varnish; proofed intaglio in black and then overprinted in relief with colour rolled onto plate and wiped away where not required.

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