Rendering Amber Clear for Use in Lens-Making for Magnifying Glass

Pencil sketch of Sir Charles Lock Eastlake by John Partridge (Queen Victoria’s favourite portrait painter), 1825

From the work of Sir Charles Lock Eastlake entitled Materials for a history of oil painting, (London: Longman, Brown, Green, and Longmans, 1846), we learn the following:

The effect of oil at certain temperatures, in penetrating “the minute pores of the amber” (as Hoffman elsewhere writes), is still more strikingly exemplified in an invention, or perhaps and old method revived, Christian Porschinen of Königsberg, at the close of the seventeenth century (June, 1691).  He succeeded in rendering amber colourless, so as to employ it as substitute for magnifying glasses.  Zedler ( Grosses vollständiges Univ. Lexicon, art. Bersteinerner Brenn-Spiegel) describes the process.  The manufacturer placed the amber, already formed and polished for the intended use, in linseed oil exposed to a moderate fire, and suffered it to remain till it had entirely lost its yellow colour, and had become quite clear and transparent.  Zedler states that lenses so prepared are more powerful than those made of glass in igniting gunpowder (welche viel schneller in Brennen and Pulver-anzunden sind als die glasernen).

The same process was afterwards adopted for clarifying amber beads, so as to render them transparent like glass.  The method is probably most successful when the substance is not very thick.  For a further account of this invention Zedler refers to Hen. von Sanden, Disp. de Succino Electricorum principe, Königsberg, 1714.  Dreme (Der Virniss-und Kittmacher) alludes to similar methods.  “Amber boiled in linseed oil is softened so that it may be bent and compressed: opaque or clouded amber by this process becomes light and transparent.  The oil should be heated gradually, otherwise, the pieces of amber are liable to crack. ”  Such modes of clarifying amber might be employed with effect, preparatory to its solution by some of the means before indicated.

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