On 20 Oct 2021, at 17:49, Ad Stijnman <[log in to unmask]> wrote:

Thank you, Elizabeth, this is very worthwhile information. At least to me, because it is the first etching recipe in Arabic that I see.

For those interested follows an analysis of the recipe (3 min. reading time).

With best wishes,

Ad.

This 13th-century recipe relates well to the oldest known occidental etched object, a sword found in the tomb of King Sancho IV of Castile and Leon in Toledo dated c.1290. Toledo was a town where Western scholars studied Arabic texts and therefore a likely place for the application of Arabic knowledge for the etched inscription just under the hilt of the sword.

The prescriptions are perfectly in line with the recipes for mordants and grounds for etching iron objects (not printing plates!) in occidental manuscripts from the (early?) 14th century onwards. The materials, tools and techniques used for the various steps in the etching process are identical.

The meaning of the Arabic recipe is that it might explain that the etching process was introduced by means of the dissemination of Arabic texts in the occidental world. This is known in other areas of scholarship and the routes were through Sicily and Spain, where both cultures mingled and exchanged information in the 12th and 13th century. Less so via the Byzantine empire. Iron or steel weapons, armour, tools, etc. with etched ornaments are found throughout Europe from the 14th century. The Augsburg armourer Daniel Hopfer (c.1470–1536) used this knowledge to create the first etched iron printing plates from the middle of the 1490s. A number of his plates still survive.

Incidentally, it shows that a form of oil paint (the mixture of 'minium and flaxseed oil') was known to the oriental world in parallel to the development of oil painting in the western world in the 13th century. I would love hear if anyone knows of any discussion on the knowledge of oil paint in the oriental world pre-Van Eyck.

Otherwise, the mentioned materials were all documented in Western sources starting with the Luca Codex 490 (c.800), various copies of the Mappae claviculae (9th century and later), Heraclius (10th century) and the Codex Matritensis 19 (12th century), possibly also the Manuscript Cotton Julius D. V (13th (?) century) in the British Museum. They give recipes for gilding (deaurare) iron objects by means of a solution of copper salts in vinegar. The gilding appears in seconds, i.e. the iron is coated with a thin, shiny layer of pure copper atoms. None of these recipes prescribe to continue the process, which would cause corrosion (superficial etching) of the iron object after some hours.

Breaking down the text:

- coating the iron object: (a) with a mixture of minium (red lead, Pb3O4) and linseed oil, i.e. a kind of oil paint; the lead constituent will cause the drying of the oil by means of oxidative polymerisation, which may take a few weeks before the layer is hard enough to draw a stylus through it

- or, coating the iron object: (b) with melted wax; the wax cools and hardens instantly on touching the iron and can be drawn through with a stylus.

Both materials are mentioned in many Western sources on etching after 1300.

- drawing in the coating with a needle or the tip of a knife, just touching the iron; this hasn't changed since, it is still the manner in which etchings are drawn.

Alternatively a design may be drawn on the metal with melted wax (difficult, in my experience, because the wax cools and hardens instantly) or the oil-paint (works fine).

The recipe for the etching fluid (etchant, mordant):

- 1 part 'sal ammoniac' (NH4Cl)

- 1 part of 'salt' (presumably plain kitchen salt, NaCl)

- dissolve in 'good vinegar'; normal vinegar contains 2–4% acetic acid (CH3COOH), which gives a slow chemical reaction; most recipes recommend strong vinegar, i.e. containing 5–8% acetic acid, which works faster

Vinegar only has little immediate effect on iron, but the chlorides in the solution propel the chemical reaction.

Using water as alternative to vinegar will have little effect on the short term in creating a tangible relief.

The etching process:

- 'cover the coated surface with the fluid', i.e. fill a vessel with the solution and place the object in the solution until completely immersed; alternatively it is found to build a wall of beeswax around the area to be etched and pour the solution within it

- 'let stand overnight'; this is a short period of time, i.e. some corrosion will be visible, but the grooves made may not be tangible

- 'some say to use verdigris instead of salt'; recipes for etching iron or steel containing copper salts such as verdigris (copper acetate, Cu(CH3OO)2) or copper(2) sulphate (CuSO4) are commonly mentioned from 1300 onwards; the copper-ions in the fluid create an electrolytical reaction with the iron, by which iron-ions part from the object and go into solution; this is a slow process, taking hours, but in the presence of chlorides takes only a quarter of an hour for tangible results; as explained above, if the object is only shortly dipped into the solution the iron will be coated with copper.

For further details and references see my Engraving and Etching 1400–2000, pp. 45–50.

Op 20-10-2021 16:25 schreef Elizabeth Savage <[log in to unmask]>:

Dear Blocks Plates Stoners

This might be slightly off topic, but possibly of interest to those of you interested in the history of etching:

Joumana Medlej has tweeted a thread on her experiments to recreate 13th-century instructions for etching on iron https://twitter.com/joumajnouna/status/1442119876613713925?s=20 . The instructions are below, and the thread illustrates each step.

With best wishes

Elizabeth

––––

Dr Elizabeth Savage FRHistS FSA (she/her)
Senior Lecturer in Book History and Communications
Institute of English Studies
School of Advanced Study, University of London
Room 255, Senate House, Malet Street
London WC1E 7HU

Co-Director, Book and Print Initiative
2020/21 Honourary Fellow, Centre for the Study of the Book, Bodleian Libraries
2020–2022 British Academy/Leverhulme Small Grant: Fladerpapier: Art, Craft, and the Earliest Mass-Produced Wallpaper in the West

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Early Colour Printing: German Renaissance Woodcuts at the British Museum, http://bit.ly/SavageBMPrints

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