Etching: Preparing the Plate

Etching is an indirect intaglio technique in which marks are etched using metal points through the action of corrosive agents on a metal plate. In indirect intaglio, the most commonly used plates are zinc and copper, while the corrosive agents can be acids, such as nitric acid for zinc, or salts, such as ferric chloride for copper.

To achieve the desired engraving, preliminary steps must be carried out on the plate to prepare it for etching.

PROTECTING THE PLATE

- Adhesive plastic

- Packing tape (optional)

- Satin varnish / Hard ground

- Heated plate (optional)

A crucial precaution before proceeding with the etching process is always to protect the back of the plate to prevent it from being bitten by the mordant. This action helps to preserve the corrosive agent’s potency, protect the plate from unwanted etching, and allows for future use of the back as a new surface for engraving.

I recommend using adhesive plastic, which is easily found in hardware stores. Unlike adhesive tape, it is more resistant and can be used throughout the entire engraving process up to the final printing stage.

To apply it, use a straight edge to avoid air bubbles, ensuring that different pieces do not overlap. Overlapping plastic can deform the plate under the high pressure of the press during printing. If possible, apply a single sheet of plastic for better results.

Various products can be used as protective varnishes, but in this case, I choose satin varnish.

The plate, protected on the back and degreased, is placed on a raised support, preferably smaller than the plate itself, to prevent varnish from spreading to the back. Satin varnish is a liquid bitumen-based varnish mixed with beeswax and lamp black. Compared to hard wax (a more economical option), satin varnish offers some advantages: it penetrates more easily into already engraved marks, does not require a roller or a heated plate for application, and can be spread using a natural-bristle brush.

To apply the varnish, use a soft ox-hair brush, which prevents deep brush marks on the plate thanks to its flexibility.

A useful trick is to prepare a container with a brush (minimum size: 40mm) fixed inside the lid, allowing for easy access without needing to clean the brush every time.

The application should be as even as possible—only a thin layer is needed, as a thick coat will prolong drying time. If brush strokes are visible, the plate can be placed on a heated surface for about 30 seconds to melt the varnish further and smooth out the layer.

Once the varnish is applied, allow it to air dry until fully set (15–20 minutes); a fan can help speed up the process. When dry, the plate is ready for engraving.

SMOKING (OPTIONAL)

- Metal hangers

- Narrow fire-resistant cylinder

- White petroleum

The smoking process darkens the plate, increasing the contrast between the wax and the engraved surface. Originally, it was used extensively on copper plates since their color closely matches that of the satin varnish. Today, this step is not essential for etching, but it can still be useful for those who wish to experiment, even on plates made of other metals.

Once the satin varnish has been applied and is still fresh, place the plate face down, securing the edges onto a sturdy iron rod with two eyelets at the ends and a hook for attachment.

Alternatively, use two metal hangers, resting the front of the plate on the two metal wires. Use a cotton cloth soaked in white petroleum inside a narrow, heat-resistant cylinder. When ignited, the petroleum produces dense black smoke. By moving the cylinder close to the plate, the surface becomes darkened. This happens because the heat of the flame melts the varnish slightly, allowing it to mix with the soot from the burning cloth. It is important to keep the flame moving constantly to avoid overheating the plate, which could cause excessive drying of the varnish and subsequent cracking during engraving.

Once the smoking process is complete, allow the plate to cool. Once ready, it can be engraved.