Glass from the Spessart: Forest Glass - German/German

With around 150 smelting sites, the Spessart was one of the most important glassmaking areas of the late Middle Ages and the early modern period. The glassmakers north of the Alps produced masses of green forest glass in the large forest areas from the 14th century onwards: tumblers, roman glasses, fitting glasses, thumblers and bottles. Because of the enormous demand for wood, the glassworks were located in the middle of the forest. That is why the glassworks were also called forest glassworks. The glass that was produced in these huts was called forest glass.

The striking feature of these glasses is their green colour, which is due to the iron oxide content in the sand, the main raw material for melting glass. The fact that glass was still very expensive as a commodity at that time was mainly due to the high energy requirements. In the Spessart region, this demand was met exclusively with wood until the 19th century. The glassworks needed wood for the glass melting furnaces and for the production of potash to lower the melting temperatures. Potash was made from beech wood. Huge quantities of wood had to be bought expensively from the surrounding forests. So the sovereigns made a lot of money from the sale of wood.

To illustrate the enormous energy requirements, the Fürstlich Löwenstein-Wertheim-Freudenberg administration donated a 200-kilogram, 150-centimetre-high beechwood tree trunk with a diameter of 50 centimetres to the glass museum. The Spessart glassmakers were only able to produce one kilogram of glass with it. Just five small cups were made from it. Today, 800 kilograms of glass could be produced with this tree trunk, i.e. 800 times as much as at that time.

 

Spessart Glass: Forest Glass - English

During the late Middle Ages and early modern era Spessart had around 150 small glass foundries and was one of the most prominent glassmaking areas. From the 14th century onwards the glassmakers in the large forest areas north of the Alps produced masses of green Forest Glass. Beakers, rummers, "pass," glasses, thumb glasses and bottles. The foundries were located in the middle of the forest because they used enormous amounts of wood, which is why the glass that was produced in them is called Forest Glass.

 The characteristic green colour of this glass comes from the iron oxide particles in the sand used as the main raw material for the molten glass. Glass was a very expensive article of daily use at the time because of the high-energy requirements needed to produce it and wood continued to be exclusively used for this purpose in Spessart into the 19th-century. The foundries used wood both for powering the furnaces and as potash to reduce smelting temperatures. Potash was made from birchwood and huge amounts of wood had to be bought at high prices from surrounding forests. Thus territorial lords made an excellent living by selling it.

In order to demonstrate the enormous energy requirements to you the Royal Löwenstein-Wertheim-Freudenberg'sche Administration gave the museum a 150 cm-high beech wood tree trunk with a diameter of 50 cm, weighing 200 kg, with which Spessart glassmakers would have produced just one kilogram of glass: or five small beakers. Nowadays 800 kg of glass, that's eight times the amount, could be produced from this tree trunk.