Intaglio printing process
In the intaglio method of printing, we are talking about using a matrix which has the image below the surface.
When ready for printing, ink sits in the lines below the surface of the matrix, and pressure is applied using a rolling motion with an intaglio press, forcing the ink out of the inked lines in the matrix onto the paper.
The word intaglio comes from the Italian intagliare, to cut, and refers to the method of cutting, or incising, lines into a surface, to produce an image. Jewellers and sculptors had been using this method since antiquity, but it was not until the 1430’s in Western Europe that this technique was first applied to a flat piece of metal with the express purpose of transferring the image to paper.
In this post, I’ll be using an etched copper plate as the matrix to describe the intaglio printing process. The process of producing the actual matrix will be described in another post – this is a discussion of the basic printing process – however it is worth noting that the three main methods of producing an intaglio plate before 1600 were engraving, drypoint, and etching. Some of the equipment/method used will be modern, but this will be noted. However, in essence, the modern method is still very close to its 15th Century counterpart.
Before the very first printing of a prepared metal plate, the edges must be filed. They are filed down at a 45 degree (approximate) angle away from the upper surface. This prevents the sharp metal edges of the plate from cutting the paper, or the blankets of the press. For more information, see File Your Edges.
The ink is then made ready. As with relief printing, there needs to be a flat, clean, smooth surface for the printing ink. A glass or marble slab is ideal, but any very smooth surface can be used. A portion of ink is set out on the slab and worked with a knife or palette knife to ensure it is neither too stiff nor too soft, and that there is no dried ink or foreign matter present. If the ink is too stiff, a little boiled linseed oil may be added, or the plate may be warmed on a hotplate – but not too hot, or a metal matrix may be damaged through buckling or cracking. If the ink is too soft, some pigment may be added.
Intaglio ink is oil-based, as water-based inks can dry too quickly on the matrix. Furthermore, because the paper used is damp, water-based inks may result in the image bleeding. Each intaglio printer would make their own inks up according to their own preference, or to achieve different results. For the most part, modern intaglio inks are still made the same way as early inks, using a mixture of boiled linseed oil, pigment, and sometimes rosin/varnish, in varying amounts.
Ink is now forced into the incised/etched lines on the matrix, and in doing so, the entire surface becomes covered, in order to drive the ink below the surface uniformly. This is done using a dauber, also known as a dabber or tamp – or if it is very small, sometimes called a dolly (from the French, poupee, especially if there is more than one colour being used on the plate). Most follow the same form of either a roll or pad of tarlatan, a coarsely-woven form of muslin.
The matrix surface is then wiped clean, using a ball of tarlatan which has been teased and rubbed to soften the sizing (which is usually added so that the material has enough body to be rolled onto a bolt).
First there are broad strokes to remove the bulk of the ink. Then, there are smaller, gentler, circular motions, to ensure the plate is not wiped more in any one direction, which may accidentally result in overwiping (removing ink from the lines, instead of just the surface).
Finally, the matrix may be finished by either hand-wiping – using the heel and pad of the palm (usually with a light coat of whiting, which is washed white chalk) – or very gently wiping with a soft, clean pad of rag, to remove any residue of ink or marks left by the coarse weave of the tarlatan. There is no firm evidence that hand-wiping was used before 1600, but it was a standard method for wiping engraved copper plates by the 17th Century. The whiting prevented any oil on the hand from transferring to the plate, and gently polished the copper surface. Too much whiting on the hand, however, can result in loose particles ending up in the inked lines, preventing a good result. Certainly soft rags were used, but either way, it must be done very carefully, because it is at this point that overwiping can easily occur – a balance must be made between cleaning of the surface, and retention of ink.
The corners are then carefully cleaned with a rag, and the matrix is ready to be printed.
The matrix is placed on the bed of an intaglio press and covered with a dampened sheet of printing paper and the press blankets.
It is passed through the rollers of the press at high pressure by manual turning of the press wheel. The roller action forces the ink out of lines on the matrix onto the paper.
The blankets, made from felted woollen cloth, create a ‘buffer’ which protects the paper and the plate from the force of the rollers. They also help push the paper into the matrix, and absorb excess water from the paper. Consequently, they are damp at the end of a day’s printing.
The paper is dampened so that it is flexible enough to be forced into contact with the inked, recessed lines without buckling or tearing. Usually this is achieved by soaking in a tray of clean water, with the length of time determined by the thickness (weight) and rag content of the paper. Western Europe used pulped linen rag for paper production almost exclusively in the time period we are discussing, as cotton was not widely used in cloth manufacturing, and wood pulp had not been developed. Intaglio papers are not usually sized, as sizing interferes with absorption of water, and transfer of ink. A modern printing paper is usually a rag/pulp mix, and is soaked for about 10 minutes. If many sheets are being soaked at once, they can also be drained and wrapped in a bundle to prevent drying out, and used over the course of some hours or a day. Before each piece of paper is used, it is placed on a clean towel, covered with another, and gently smoothed/patted to remove excess water, but not pressed with the hands – the paper must not be distorted or have too much water removed.
After the plate and paper have passed through and are fully clear of the rollers, the blankets are folded back carefully, and the paper is peeled/pulled away, to reveal the print.
The pressure of the intaglio press flattens the texture of the paper where it makes contact with the matrix. The edge of the matrix should leave a smooth, firm, uniform impression where it made contact with the paper – which is why the edges should be cleaned well. Often the lines of the image can be seen on the reverse (verso) of the paper, sometimes even after the print is flattened.
The damp print now needs to be dried, for both the ink and the paper are still wet. In the time period we are discussing, this seems to have been a two-fold process.
In images of intaglio printing studios, multiple prints can be seen draped over rods or ropes, image facing upwards, bending in half as they dry. This will ensure that the ink dries faster (perhaps 2-3 days) with air contact, but leaves the paper distorted. The print would have to be dampened again, once the ink is dry, so that it can be pressed flat between boards and weights.
In modern methods, this is also sometimes done, but it is much more common to press the print as soon as it is removed from the bed of the press. It is placed, with paper and ink still damp, on a sheet of cardboard, and covered with clean scrap paper (such as newsprint, which is bought unused in a ream) which acts as a blotter. This results in very little transfer of excess ink from the image, because the blotter is more likely to absorb water from the paper than oil-based ink from the image. The next sheet of cardboard is placed over the top, and the process continues to create layers of cardboard, print, and scrap/blotter, which are then finished off with a final sheet of cardboard, and sheets of wood, over which are placed heavy, even weights.
In this way, the paper and ink dry in one process, but takes longer for the oil-based ink to dry (5-7 days), because of the lack of contact with the atmosphere. However – and this is why I believe it was not used pre-1600 – this method takes up a large amount of paper product. In this time period, paper was finally being mass-produced, allowing printing to be economically viable, but not in any quantity approaching modern standards. The concept of using virgin paper, even of cheap quality, as scrap or blotter which cannot be reused would probably have been seen as wasteful and expensive.
Regardless of method, the process of flattening the print reduces the amount of the physical impression visible on the surface – for example, it will flatten most of the impression left by the edge of the matrix.
After being flattened the print is then more suitable for use, for example, as leaves/pages in a book, or tipped (glued) into an existing book, as an image to be pasted onto a wall or inside a box (sometimes called Coffrets à estampe), put into a display cabinet, or folio, or any number of other uses which will be discussed in a future post.
Finally, at the end of the printing day, the press blankets are removed to be hung and aired, the towels for paper must be dried, the ink cleaned from the slab and the matrix cleaned. The matrix would be wrapped in a clean cloth, perhaps first with a thin layer of oil applied. If a metal plate was not going to be used again for a very long period of time and put into storage, it might be coated in pitch or tar to preserve the image and protect it from moisture. Tools such as daubers would have been wrapped in damp cloths to prevent their drying out – speaking as someone who lives in modern-day Sydney, this is something not being replicated. The best and closest practice is probably to wrap tightly in aluminium foil.