Gold ruby glass
Gold ruby glass is a collective name for pale pink to dark red glasses that are colored with colloidal gold dissolved in the glass melt . The color effective pigment is gold purple . The color does not appear black even in a greater layer thickness. The color is only imperfectly visible in the glass that has cooled down from the melt and only appears in its full color strength when it is reheated, as it is a so-called tarnish color. As a result of diffusion processes, the colloidal particles form in the glass when it is heated again. The coloring of gold ruby glass is produced by the excitation of plasmons , whereby the plasmon resonance frequency depends on the size and shape of the gold nanoparticles. For spherical gold nanoparticles, the resonance frequency is typically 510 to 540 nm, which leads to the typically red color of the glass.
Among other things, soda-lime glass and lead glass can be colored to make gold ruby glass. Most of the gold ruby glasses available on the market contain a certain amount of lead oxide , as this helps the formation of colloids. Another component is often tin , which is added in metallic form as a reducing agent. On borosilicate glass , pink-violet colors can be produced by vapor deposition with gold.
It is used for drinking glasses, glass windows and traffic lights, but has been almost completely replaced by the much cheaper and more yellowish selenium ruby glass . In addition, there is a copper ruby glass with a brown tinge . A very old example is in Diatrettechnik produced Lykurgosbecher .
This way of coloring glass was first mentioned by Giambattista della Porta in his Magia naturalis . In the edition of Naples 1589 it says in the 6th book, 9th chapter (p. 123) De smalto rosei clari coloris conficiendo : “Floridissimum rosae colorem in vitra perspicies, quo exornando auro uti poteris” - “you will become the most blooming color of the rose see in the glass if you can use gold as an ingredient ”. A little later it is mentioned by Antonius Neri in L'Arte Vetraria (Chapter 129 in Book 7). Johann Christian Orschall published a preparation recipe for ruby glass in 1682. Johannes Kunckel later refined the recipes until they were ready for production (around 1680). Another method for gold purple production comes from the Hamburg doctor Andreas Cassius (published 1685).
Web links
Individual evidence
- ↑ Ludovico Cademartiri, Geoffrey A. Ozin: Concepts of Nanochemistry. Wiley-VCH, Weinheim 2009, ISBN 978-3-527-32597-9 .
- ↑ See The Lycurgus Cup on britishmuseum.org
- ^ L. B. Hunt: The True Story of Purple of Cassius. The birth of gold-based glass and enamel colors. P. 137 ( digitized version ).