The invention of the movable type printing press was certainly a fundamental turning point in the history of books.

From the point of view of image printing, different techniques, through the use of different materials and tools, have been utilised over the centuries.

The following provides some of the most widely used techniques, for which there are examples in the books of the Library of the Botanical Garden.

Xylography / wood engraving (or "high press")  

From xylon = wood + graphos = mark -> mark produced by a wooden matrix.

This can be done by carving with the use of tools such as knives, chisels or gouges or by engraving, with tools such as burins.

It is the oldest method of engraving, practiced in China from the eighth century AD and used in Europe since the thirteenth century for the decoration of fabrics, religious images and playing cards. It is also the first printing technique of text characters.

How it’s done: the wood slab, which can come from different types of trees, is processed through the removal of all the parts that are not supposed to hold the design but remain white, obtaining a relief image; the ink is evenly distributed using swabs or, from the nineteenth century onwards, rolls. Achievement of the design is limited by the lack of uniformity of the wood’s surface due to its grain, as well as from its mechanical fragility, elements that do not make it possible to obtain a very high degree of detail.

Preparation of a matrix for xylography  (from Wikimedia).

In the early years, wood-cut matrices were used exclusively (i.e., obtained by cutting the trunk of a softwood tree, such as cherry, vertically), which caused greater difficulties in processing due to the presence of the grain. Starting from the second half of the eighteenth century (though there are older examples), these were replaced by end-grain wood matrices (obtained by cutting horizontally the trunk of a hardwood tree, but fine-grained, such as box), which thanks to the greater uniformity in the resistance by the fibres, allowed for more detailed workmanship and the use of the burin, with which more precise and subtle impressions can be obtained.

Already since the beginning of the sixteenth century the first experiments with colour chalcography began through the use of more wooden matrices with the same design, inked with different shades of the same colour and then impressed in succession on the same sheet. It was a very complex process and often inaccurate, and in most cases the images were printed in black and white and then hand-painted.

Video produced by the La Luna cultural association, in which the engraver Alfredo Bartolomeoli makes a wood engraving.

This technique is used in some volumes on the Library, such as: Incipit herbarium Apulei Platonici ad Marcum Agrippam, Herbarum vivae eicones ad naturae imitationem, Primi de stirpium historia commentariorum tomi vivae imagines, I discorsi di M. Pietro Andrea Matthioli, Theatrum florae in quo ex toto orbe selecti.

Lithography

From lithos = stone + graphos = mark -> mark obtained from stone

This printing technique was developed in 1796 or 1798 by Alois Senefelder, based on the capacity of some stones to retain a thin layer of water and, on the contrary, the repulsion that fatty and oily substances have to water.

Procedure: the stone slab (which must be calcium carbonate limestone) is carefully smoothed and subsequently drawn (in a specular way with respect to the image to be obtained) with a grease pencil; the plate is then treated with a mixture of nitric acid, acidified gum arabic and water, which acts only on parts not protected by the traces of the pencil, making them hydrophilic. The matrix is ​​then wet and inked: the ink adheres to the fatty parts and is rejected by the wetted parts and the image can thus be imprinted by the use of a printing press.

Stone for lithography drawn in the negative (left) and the resulting printed image in the positive (right) - Image taken from Chris 73 / Wikimedia Commons

This technique is used in some volumes on the Library, such as: Description des plantes rares cultivées a Malmaison et a Navarre.

Chalcography

From calcos = copper + graphos = mark -> mark produced by a copper matrix (or more generically by a metal matrix).

The technique is also called "gravure print" from the moment that the matrix is ​​processed to obtain a hollow design, intended to then hold the ink to be transferred onto the paper. The design on the matrix can be achieved in two ways:

• Direct action = use of a mechanical instrument, in particular the burin, through which the engraver removes the metal directly
• Indirect action = is the etching technique, obtained through the controlled action of corrosive chemical agents: the metal matrix is ​​protected by a varnish, engraved with a metal tip and then immersed in a solution of water and acid that acts only on the etched parts (thus no longer protected by the varnish)

Before the impression, it is necessary to carry out thorough cleaning of ink from the surface of the matrix.

The image represents the different moments of creating a chalcography through indirect action:

1. a protective primer is applied to the metal plate, upon which the image to be printed is then drawn (in reverse);
2. the metal plate is immersed in an acidic solution, which corrodes the drawn parts, and are therefore left without protection;
3. the plate is cleaned and washed to remove both the acidic solution and the protective primer and treated with a solution that counteracts the action of the acid, to stop it;
4. the metal plate is then inked (the ink enters into the spaces of the drawing), cleaned and then printed with the use of a press or rollers.

Usual steps to make a chalcography (image by Carola Barnabas DensityDesign Research Lab, from Wikipedia)

The metal plates used are generally copper, but there are also examples of the use of other metals such as bronze.

This technique is used in some volumes in the Library, such as: Variae ac multiformes florum species, Hortus botanicus Vindobonensis.

Impression

The technique, similar in many aspects to that of the smoke printing, consisted in sprinkling ink on the surface of the plant, and then imprinting it on a white sheet in such a way that would leave its mark.

This is a technique in use at least since the first half of the fifteenth century (the oldest example is preserved at the University Library of Salzburg and dates back to the years just preceding 1425), which places it just between the choice to collect dried plants (hence the real specimens) and to represent them through illustrations.

There are no examples of this technique in the books presented in this exhibition.

Smoke printing

A technique used since at least the fifteenth century until the beginning of the nineteenth. It consisted in exposing dry plants to the smoke of a candle or an oil lamp until they were uniformly covered with soot. The plants were then positioned above a soft paper, which was flattened with a rod until the soot remained on the paper.

It is a direct printing technique, since there is no need for the use of a matrix.

Over the years, soot was replaced by ink, which led to prints being less subject to deterioration.

The technique of direct printing with ink could also be used to impress the wood slabs to carve for the xylograph process (with the development of photographic processes, a photosensitive film was then applied to the matrix, which was impressed and the imprint served to guide the incisions).

An early example of the use of smoke printing can be seen in the Codex Atlanticus by Leonardo da Vinci (between 1490 and 1519, folio 197 verso), although the method allows for a "positive" print, i.e. black tainting of the paper and then impressing the object to be printed on it, in such a way that transfers the colour from the corresponding part of the sheet to its surface, leaving a white area. This is the text of Leonardo: "This paper must be tinted with candle smoke tempered with fresh glue and then subtly smearing the white lead sheet with oil, like the way letters are impressed, and then impress as usual. And so the sheet remains dark in the empty spaces and light in the reliefs. What happens is the opposite here." The text is accompanied by the image of a sage leaf printed in negative, thus the black is spread on the object and not on the paper (hence the reference to the "opposite" in the last sentence).

This technique is used in some volumes in the Library, such as: Stirpium specimina calcata, Flora Berolinensis.

Physiotypia or physiography

Also known as "natural print" (in German "naturselbstdruck"), the chalcographic technique was already tried many times in the Middle Ages. It was most probably improved in the mid-nineteenth century around Vienna thanks to Alois Auer. It consists of an impression by means of a press or a roller of an object (e.g. leaf, lace, feather...) on the surface of a sheet of lead: lead, being a very soft metal, retains the imprint of the object, which is then filled with ink, creating a matrix usable for printing.

Example of a physiotypic print of a bat (from Brandbook.de)

A method, as described by the author: “Placing the original whether a plant, a flower, an insect [...] between a copper sheet and a lead sheet and then moving them between two tight cylinders. The original leaves, thanks to the pressure, the imprint of its image with all the details of its fabric, and so to speak its entire surface, on the lead sheet. By applying impressions of colours on this lead sheet, such as in printing of branches, with each impression of the plate, there is copy of the striking resemblance to the original, and with the greatest variety of colours” (from Exposé read in the mathematics and natural sciences class from the Imperial Academy of Sciences in Vienna by Louis Auer i.r. Regency Counselor... – granted by rescript dated 12 October 1852, n. 7698, Vienna).

This technique is used in some volumes on the Library, Flora of Northern Italy illustrated with physiotipya.

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