NEW PLATE GROUNDING METHODS The reasons for not using a ground of melted wax and asphaltum are not just health, but because the substitute - linseed-oil based relief printing ink - is so versatile that it can replace hard ground, soft ground and aquatint, if you are galv-etching the plate, and then can produce effects impossible with the traditional methods. The reason is that an ink ground in acid (even weak ferric chloride) is broken down, lines are widened, and there is often foul-biting, whereas with galv-etch, the oily ink film electrically insulates the plate and the biting proceeds only in uninsulated areas. The way galv-etch works without clogging fine lines or texture with bubbles, precipitate or a crust, means a completely clean bite, without any need for attention to it, except to check periodically for pinholes or depth of bite. (TOP) I use non-skinning black ink (or white ink sometimes on copper) thinned with raw linseed oil, and a few drops of cobalt dryers to speed up hardening, rolled onto the cleaned plate with a soft treothene roller. The exact viscosity of the ink must be judged from experience, but I have found that the viscosity and thickness on a plate that prints well in relief is right for a ground. When it is dry it can be needled with all the usual tools, and generally treated as you would a traditional ground. It is more resistant to accidental scratches and can be drawn on with spirit-based felt pens. It can be cleaned off with ethanol (95% industrial ethyl alcohol), followed by cream non-abrasive bath cleaner. An alternative to using Cobalt drier is to dry the plate in the sun, which seems to produce a better ground in the end. Another advantage is that you can work on the plate out-of-doors and full sunlight will not melt the ground and reseal the lines, which happens so easily with traditional wax grounds. (TOP)
An insulating ink ground behaves in some ways like a traditional soft ground while it is wet, and if you draw through a textured paper over the inked plate, the etched plate will produce a result similar to a soft ground etching, except that the evenness of the ink ground, and the nature of the galv-etch bite will produce a much more sensitive impression, and a greater variety of responses to types of paper, hardness and shape of pencil etc. Similarly, if the grounded plate is put through the press with a textured absorbent surface, and left to dry, stopped where necessary with ethanol/shellac varnish, and then galv-etched, it will produce texture in a similar way. Cobalt dryers should definitely not be used in the case of a soft ink ground, so you may have to wait longer for it to harden in the sun, under an ultra-violet lamp, or risk galv-etching it while it is wet, using a very low voltage and amperage. Traditional soft ground also requires a very low voltage and amperage with galv-etch, and so if you are using a 6/12 volt battery charger as your power supply, use the control box shown on page 14 to switch to the lowest voltage possible. (TOP)
|
