Glossary

Annealing

Like most materials, glass dilates with the effect of the heat and contracts when it is cooled down. If a hot glass item is cooled down suddenly, the walls will stiffen whereas the heart of the item , still at a very high temperature, will be dilating. This creates significant stresses likely to cause the items to break or shatter.
The annealing process eliminates these stresses and allows the production of resistant products. To begin with, the operation consists in reheating the item up to 500°C approximately and ,subsequently, in cooling it down very slowly to maintain a uniform temperature.

bowl

The bowl designates the part of the glass (stemmed glass or tumbler), which holds the liquid.

Casing

Casing is a technique that dates back to Ancient times and which consists of superimposing layers of lead crystal, one of which is coloured.

cullet

Cullet is the name given to the broken glass, which is added to the mix of raw materials, before the fusion.

Engraving

Engraving is a decoration technique achieved with a wheel, acid or a pantograph.

feeders

Feeders are pieces of equipment designed to feed the molten glass to the moulds mounted on automatic machines.

finish

Once the item has reached its shape, the finish is the step which will give it its final appearance (decoration, cutting, engraving…)

Flux

Flux is a basic oxide (soda, potassium hydroxide, lime, lead oxide) used to melt the silica more easily during the glass melting process.

foot

The foot designates the stem and the base of the glass.

Frosting

Frosting is a process, which gives the material a matt finish. It is achieved with sand blasting, acid-etching or with a grinding wheel.

Furnaces

Furnaces are used to melt glass.

Fusion

Fusion is a crucial step during the glass manufacturing process since it transforms the composition of the raw materials into glass. Raw materials are mixed and heated in the furnaces at very high temperatures to enable the glass to reach a liquid state.

Glass

• sodalime : Sodalime glass is used in the manufacture of items such as stemmed glasses, vases, cups, salad bowl but also for the production of decanters, preserve jars and jugs.
• It is also used in the building industry for windows and in the car industry for windscreens, lights :
- 100 % recyclable
- Totally non-porous for absolute hygiene
- Big resistance to mechanical shocks (2 to 3 times more than traditional dinnerware) and thermal shocks as well as scratches
- lighter than china
- dishwasher safe
• borosilicate : Borosilicate gives cookware (casseroles, dishes) specific properties such as :
- resistance to thermal shocks
- easy cleaning owing to a specific surface treatment
- suitable for use in traditional ovens and microwave ovens
- extra hygiene due to the totally smooth surface which prevents the formation of food incrustation
- transparency that facilitates supervision during the cooking
Borosilicate is also used in the pharmaceutical field for neutral glass and in the industrial sector for lighting, washing machines windows and some other specific use (pouring jugs , cafetières…).
• Vitroceramic : Non-porous, vitroceramic is completely safe and hygienic. It has a very high heat retention and can withstand easily sudden variations in temperature , enabling the transfer from cold to hot and vice-versa.
Its properties make vitroceramic compatible with all cooking systems (bar induction): flame, halogen plate, traditional oven, electric plate, microwave oven.

Lead crystal

Lead crystal is the result of the fusion of three main components , at approximately 1500 degrees: sand, potassium hydroxide or soda and lime just like glass but with a little extra that makes all the difference : lead. Lead crystal, the purest, must contain a minimum of 24 % lead oxide. A lead crystal with 32 % lead oxide content also exists but it is increasingly rare because of its fragility.

Lehrs

Lehrs are secondary furnaces positioned around the main furnace and their purpose is to anneal the items.

Polishing

Polishing consists of buffing and eliminating the last impurities by dipping the item in an acid bath or by brushing it with soft materials.

rim

The rim is the name of the upper part of the glass, which is in contact with the lips (edge of the glass).

Silica

Silica plays a significant role in the composition of glass ( 60 to 70 %). It comes in the shape of sand, sandstone, stones, and quartz.

stem

The stem is the part of the glass that connects the foot to the bowl.

Tempered or toughened glass

A sudden drop in temperature hardens toughened glass in order to make it very resistant. Read more about the tempering.

Tempering

Tempering also known as toughening involves reheating the glass evenly (500°C approximately) to allow the material to dilate and then cooling it down suddenly, by circulating air on all sides of the glass.
Whilst increasing the resistance of the glass to mechanical shocks and sudden variations in temperature significantly, this process also reduces the potential dangers of glass because, in case of breakage the pieces will be very small and blunt.