Asphaltum

Gettens and Stout Notes
'Asphalt (bitumen) is a brownish black, native mixture of hydrocarbons with oxygen, sulphur, and nitrogen, and often occurs as an amorphous, solid or semi-solid liquid in regions of natural oil deposits. It is thought to be formed from the evaporation of the lighter components of the petroleum and from polymerisation and partial oxidation of the residue. It is found widely, but that used in European paintings came, perhaps, from the region of the Caucasus or the borders of the Dead Sea. In Mesopotamia and Egypt in very early times it was known and used for various purposes...The pigment is partially soluble in oil, like a stain, and gives a semi-transparent, reddish brown film. In the film, it may be occasionally observed microscopically as tiny brown flakes without structure. Only thin grains are transparent brown. It is soluble in turpentine, naphtha, and other organic solvents.
Asphaltum and other similar tarry compounds are among the least desirable pigments known because they never become permanently dry.' p94

Asphalt in Manuscript BnF Ms. Fr. 640
Notes from ‘Spat’ research by Elisabeth Kuiper and Ingeborg Kroon University of Amsterdam, see googledrive ‘what is ‘spat’?’
‘Spat’ is a material used in the preparation of molds for casting in the Ms.

They have identified many different uses of the term ‘spat’ or similar terms.

Three applications:

Asphalt as a colour preparation, which is used as a primer and for painting shades (folios 058r and 066r).

Burned asphalt, which is added to the sand mixture as a binding agent for molds used to cast large metal objects. The author suggests specifically that it should be burned with the sand from a mine (folios 041r and 085v).

Spat that is used as excellent sand for molding. It is said to be very soft and repeatedly said to originate in Augsburg (folios 106r until 137v).
“Asphalt as a color preparation (1)

The first two categories, described above, coincide with the first four pages on which the ‘spat terms’ are used. The manuscript seems to be a worker’s handbook to keep handwritten techniques of an experimenting craftsman. Although written down in a neat and tidy way, the recipes seem not to be structured in any specific order and written down while experimenting. Sections tend to include phrases like ‘I think’ and ‘some people use’ and at time there are notes scribbled in the borders of the pages that mean to alter or improve the previous directions. Assuming that the pages are arranged in chronological order and (except for additions in the margin) were more or less written this way, it might indicate that the author is unsure about materials in these first references. On the other hand, the material used for painting purposes could be ‘asphalt’: a color preparation that consists of a mixture of organic (the binding medium bitumen) and inorganic materials (fillers).7 Asphalt is a material that is chemically and physically unclear but is described in various historic manuscripts and texts related to painting. The most important conclusion regards the color of this raw asphalt, which is brown to grey.8 The material that the author describes relates to casting and is repeatedly described as white in color. This incoherence provides a fundamental obstacle for research in this direction and reveals that the author might have meant another material with the term asphalt related to color preparation as with the term asphalt related to casting. It indicates that the experimenting author practitioner might have been confused in his terminology. This is no unusual confusion though. In a time when knowledge was handed down mainly through oral tradition, terminology will have varied and multiple synonyms will have been in use at the same time. Old treatises and manuscript can be found to use enormous arrays of contradictory statements and synonymous terms of materials, like for example asphalt.9”

They list a lot of different names which could be used as synonyms or in confused ways in early manuscripts. For example: bitume de Judee, Judenpech, erdpech, bergpech, bergteer, aardpek, bergharz, judenharz, judenleim. Berrie 2007: 113-115.

Folio 119v. ‘Ways to rework Aspalt’ in MS. Bnf.

“Way to rework Aspalt

You find an earth in Germany, the color of plaster, but have long and soft filaments which are easy to handle. Grind them coarsely because they are mixed with earth and filth. Then soak them into sal ammoniac’s water, following the above indication, and make balls. Heat these balls in a potter’s furnace. Then soak it in the same water again. Filth will remain at the bottom, and the very asphalt, which is light, soft and malleable as flour is, stick to water, remain on the top, and make water cloudy. Pour this cloudy water in another pot. Then empty water, to do that tilt your pot, or sponge the water up. The very asphalt will remain at the bottom of your pot, dry it. Then soak it into sal ammoniac’s water, and use it for moulding box. If this matter shrinks in the moulding box, even if reheated and dried, you must reheat it on a good fire again, and redden it as you did for medals and flat things. This asphalt is the best matter to cast gold, silver, copper, lead and tin. Because it holds fire and reddens whenever you want, without changing. The more you use it the better it is, and does not change. First it is white, and becomes grey after being used. Take the reused asphalt for lead, tin and brass, but gold would get brittle, and wouldn’t easily be stripped of casting. Put away each asphalt separately depending on each metal.”35

They carried out this experiment.

Kuiper and Kroon suggest the following possible materials for spat:

Feldspar (both potassium and soda) - suitable molding material. But it does not correspond to the softness mentioned in various sources.

Calcite (calcium carbonate) - this could be it, as during preparation there is a chemical change and the substance obtained during processing is used in cement and plaster. But ‘the calcium hydroxide that is produced allows making a sharp impression, but the material is fragile and brittle, which makes it unsuitable for sand casting.’

Pumice or Barite - neither of these worked at all in their experiments.