Calcographic Stamping: Plate Preparation, Inking and Pressing

Calcographic Stamping Process

Stamping calcográfica: Before the work, the plates are beveled. The bevels consist of a small offset (about 45°) on the upper edges of the plate to facilitate the entry of the press cylinder, to protect the edges and to avoid metal cuts on the paper and damage to the press felts. Bevels leave a footprint on the printed paper (a characteristic of calcography). The plate is cleaned of varnish and the procedure is carried out to ensure the surface where the ink penetrates the engraved grooves is free of residues. Typically, fat-based inks are used (black smoke pigment with linseed oil).

Preparing the Plate and Bevels

The bevels protect the plate edges and help the paper pass under the roller of the press. A cleaned plate, free of varnish and foreign matter, ensures the ink penetrates only the excavated grooves. Proper cleaning and beveling help avoid unwanted metal-on-paper contact and reduce damage to the press felts.

Inking and Wiping the Plate

The plate is inked by extending the ink over the surface so that it penetrates the grooves. The excess ink is then removed so that it remains contained in the plate incisions. If a grayish veil appears on the surface (called entrapado), use a piece of gauze and pass it gently along the rows to push ink toward the edges and lift it off the surface. This action removes the veil and restores clear contrast between the engraved lines and the plate surface.

Common ink type

• Fat-based inks: Typically black smoke pigments mixed with linseed oil for calcographic work.

Color Printing Methods

Color printing in calcography can be achieved in different ways:

• Poupée method: All colors are applied to the same plate, using different little dabs or poupées (small rollers or hand-dabbers), applying different colors to specific areas and respecting the limits between them.
• Multiple plates: Each color uses a different plate. Plates are superimposed with perfect registration so each color is deposited in its rightful place. This requires precise alignment (registro) so that overlapping produces the intended effect.

Paper Requirements and Moisture

The paper used for stamping must have specific qualities according to the pressure and charge it will receive. Desired properties include:

• Resistance: The paper must withstand pressure without tearing.
• Porosity: Adequate porosity to receive the ink deposited on its surface and allow ink from the plate grooves to transfer.
• Adaptability: Ability to conform to the plate and follow the impression stroke under pressure.

It is important to know the exact amount of moisture to provide: enough to open the pores for the necessary time so the paper can receive the ink. Some papers (for example certain Japanese papers) do not require additional moistening, while others need long immersions in water to reach the correct condition for printing.

Pressing and Transfer

Once the plate is inked and the paper is properly dampened and positioned, the paper and plate are taken to the press. Pressure is applied by a press known as a tórculo (roller press). The press consists of two metallic cylinders: an upper cylinder and a lower cylinder. The upper cylinder moves and presses the elements against the lower cylinder; the action is often driven by a crank.

As the plate passes between the cylinders, the upper cylinder applies pressure which forces the paper into the engraved grooves and lifts the ink from the plate. This action transfers the printed image to the paper, leaving the matrix's reversed forms reproduced on the sheet.

Press components

• Upper cylinder: Applies pressure to the plate and paper.
• Lower cylinder: Supports and guides the plate and paper.
• Crank or drive mechanism: Moves the cylinders and feeds the plate under pressure.