This week we are marking the stained Glass Day, an unofficial holiday dedicated to the history and cultural significance of coloured glass. This day reminds us how coloured glass can transform our perception of the world, reflecting our emotions and moods.
The holiday was established in 2008 in the United States, but since then it has gained popularity in other countries as well. Its main idea is to show the beauty and uniqueness of the world. Glass can be transparent, frosted, patterned, or any colour.

Numerous decorative items – vases, bowls, jewellery, etc. – were made from coloured glass at the dawn of glass production, which was opaque as a rule. In accordance with the technologies available in those days, it was much easier to melt the coloured composition from which glass would be made than to purify it. The Egyptians began manufacturing glass circa 5–6 thousand years ago. Egypt was also the birthplace of beautiful designs that became a kind of substitute for ordinary window glass – the technique of making stained glass, which much later became very popular in Christian Europe. However, the Egyptians created them using an overlay method. In other words, coloured glass pieces were laid out like a mosaic on a transparent base. Such works were very expensive. The Sumerians used vitreous glaze to decorate the conical tiles of their temples. The ancient Greeks and Romans created products from coloured laminated glass, such as millefiori vases, amphorae and phials. During the Hellenistic period, glass mosaic panels became popular.

The earliest examples of glass contained many impurities, which made its colour appear ‘dirty.’ These impurities could be iron, sand, or marble dust. However, very soon, bright dyes began to be used in production to cover up the unattractive brownish-green hues, thereby giving the finished glass products a beautiful appearance. The lack of transparency concealed the shortcomings of the technology – bubbles and traces of unmelted sand. With the development of glassmaking, coloured glass became increasingly pure, and the colours acquired the shade desired by the craftsman. In some historical periods, coloured glass was valued more than gold.
The science of glass is one of the most important areas of the scientific legacy of Mikhail Vasilyevich Lomonosov. The scientist was just as interested in the theoretical side of things as he was in finding dyes for industrial glassmaking. He developed recipes for 112 tones and over a thousand shades of coloured smalts (opaque glass), surpassing the palette of the mosaic workshop in the Vatican. Lomonosov's work with stained glass contributed greatly to the development of the entire science of glass. He studied the processes of colouring glass with various metals and methods of obtaining transparent and opaque coloured glass more deeply than any other glass manufacturer.

Quartz sand, sodium carbonate and lime carbonate are used as the basis for the production of stained glass. A special furnace is required to create it, in which all the components are melted at a temperature of over 1700 degrees Celsius. To obtain the desired shades of coloured glass products, various dyes containing salts and metal oxides are used in the film application or smelting process. For example, copper oxides are used to obtain red, cadmium salts for yellow, and chromium or copper for green. Cobalt compounds are added to the composition to product blue products. It is particularly important to strictly adhere to the temperature values, depending on the dyes used. For example, some additives can evaporate at high temperatures (e.g., sulphides or fluorine). Modern technological capabilities allow surfaces to be coloured in various shades, from basic to the most complex and ingenious.

To mark the Stained Glass Day, we have updated 'Western European Art Glass and Ceramics' section of the museum website.

The museum Video Archive features the full version of a virtual album dedicated to art glass, with the images of works by famous French masters and art workshops from the late 19^th and early 20^th centuries: Emile Gallé, Daum Freres manufactory, Muller Frères, Escalier de Cristal, Gabriel Argy-Rousseau, François Décorchemont, Lorraine art glass factory "Burgun, Schverer & Co”, "Legra & Co" glass factory, Désirée Christian & Son and Crystal factories in St. Louis. The introductory article to the section ‘Western European Art Glass and Ceramics’ features an overview article on Western European art glassmaking at the turn of the 19th and 20th centuries.

The section ‘Articles and Reviews’ features an article entitled ‘Art glass production technologies’.

On the cover: Jug with ornamental painting. Western Europe. The 19^th century