Why and how are glass containers colored?
As mentioned in previous articles, we know that glass is made from sand, soda ash, and limestone. However, producing glass alone is not always enough; in some cases, glass needs to be colored. But why?
Let’s clarify how colors are added to glass containers. Did you know, for example, that glass color is achieved by adding various mineral oxides and salts?
There are many interesting facts to learn about the production process of glass bottles and containers. So, let’s explore how glass bottles are colored to better understand this fascinating process.
Different Colors of Glass
Glass can appear in a wide range of colors, although the most common colors used in the production of glass bottles are gray, green, and amber.
In the glass coloring process, a wide range of colors and materials are involved. In the following section, we will discuss the most common types, including green glass, amber glass, and clear glass.
Green glass
Green glass bottles are often used for storing olive oil, but they can also be used for many other products, including beverages. The greenish color of glass is typically achieved by adding chromium oxide to the glass formula. If the manufacturer wants to obtain different shades of green or additional visual effects, other materials can also be added to the formula.
Amber glass
Amber glass is commonly used in the beer, pharmaceutical, and essential oil industries. It absorbs harmful UV rays and protects the product from light exposure. To achieve the amber color, sulfur oxide, iron, and carbon can be added to the glass formula.
Clear glass
For a long time, achieving this shade was very difficult. The lighter the glass, the more effort was required in the production process. With innovative processes and new technologies, this process gradually became easier and more accessible.
When we refer to clear glass in this article, we mean transparent glass. The term “flint glass” comes from a formula created by glassmaker George Ravenscroft in 1662. He added calcined flint (pure quartz stone) to his glass formula, which made the production of clear glass easier.
Over time, several additional techniques were invented that made the production of clear glass even more accessible. Today, the most common process is color correction, which is achieved by adding pigments to the glass batch to compensate for remaining iron impurities until the glass becomes clearer and more transparent.
Reasons for Coloring Glass
Did you know that glass bottles are colored not only for aesthetic reasons, but also for safety and to protect the contents stored inside them?
The video below further explains how the choice of glass color for a bottle can affect its contents and, for example, help prevent unwanted chemical reactions in beverages such as beer and malt drinks.
