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wildbrush's art.to.day - you entered my world of technical art info - |
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The painting media - Encaustic: a. Wax used cold |
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b. Wax used cold: |
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| Punic
wax Wax that is to be used cold requires
emulsification or saponification, a process that allows
it to be diluted with egg or oil, for example. This produces
a medium with several advantages: the wax does not
have to be kept hot throughout the period of painting;
the painting does not
have to be carried out so rapidly; there is
greater control over the consistency of the medium; and it is
simpler to correct and adjust paint already applied, because
the emulsified wax dries very slowly (compared to molten
beeswax paint which very rapidly solidifies). The idea of associating Punic wax with painting has met with a great deal of criticism, for several reasons. For one thing, it was thought (mistakenly) to be hard to produce. 18) Then, the medium sometimes does not seem to be pigmented, because with the passage of centuries certain colours have faded due to the presence of sodium hydrogen carbonate or sodium bicarbonate (see below). And there is also the problem that we have no direct references to it as a painting medium in extant literary sources. Nevertheless, absence of written evidence is no proof, and a portrait in the Petrie Museum [40] on investigation revealed a gas chromatogram characteristic of Punic wax, 19) proving beyond all doubt both its existence and its use in wax paintings. Pliny and Dioscorides give very similar recipes for the production of Punic wax. 20) They are easy to follow and present no difficulty. In the series of experiments I myself conducted, under the supervision of a chemist and using the ancient authors as a guide, I produced a substance very much resembling that described by Pliny, and which on further experimentation I found to possess all the appropriate physical qualities necessary for use as a painting medium. The first stage in the experiment was to purify the crude beeswax according to Pliny's instructions, by boiling it in salt sea water and straining it through cheesecloth several times. Although Pliny and Dioscorides both suggest leaving the wax out in the sunlight and moonlight for several days in order to dry it and to bleach it, I did not find this necessary, as the wax was already sufficiently white for its intended purpose. It was then saponified by the addition of sodium hydrogen carbonate or sodium bicarbonate, the 'nitrium' of the ancient recipes; finally, the resulting substance was drained in cheesecloth, rinsed under lukewarm running tapwater, and dried at room temperature. The next stage was to assess to what extent Punic wax was usable in painting. I discovered that mixing it with small amounts of egg yolk, a few drops of linseed oil, and the desired pigment produced a very capable medium which, when used for painting, resembled the evidence of the portraits. The thick, emulsified paint of a paste-like consistency was easily applied by all sizes of brush, and permitted the finest details [as in 45 and 58]. The effect achieved by this emulsion is very similar to that of egg tempera, but with the added thickness of the wax. (Ernst Berger, the first to conduct these experiments successfully, called the result 'wax-tempera', 21) but I find that term confuses the wax and tempera techniques.) Like beeswax, Punic wax can be used in conjunction with other substances to improve its properties as a painting medium - with oil, to keep it fluid; and with egg, to make it adhere better to the surface of the support and to make it harder and more resilient. < back to page 4 page 6 > |
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