[PA-NJ Glassblowers] The Chemistry of Coloured Glass - Infographic and Web Page
Tony Patti
gaffer at glassblower.info
Thu Mar 5 09:08:35 EST 2015
Karl Carter sent me this awesome infographic and web page
http://www.compoundchem.com/2015/03/03/coloured-glass/
or
http://www.compoundchem.com/wp-content/uploads/2015/03/The-Chemistry-of-Colo
ured-Glass.pdf
Coloured glass is something thats commonplace in our lives, from the green
of wine and beer bottles, to the red, yellow, and green of traffic lights.
The origin of these colours is something we dont give a lot of thought to,
but a range of different elements are responsible. This graphic takes a
simple look at a few of these, and the colours they impart.
Before discussing the cause of colour in more depth, its worth discussing
the chemical composition of glass itself. There are actually different types
of glass for different purposes. The vast majority of the glass we use on a
daily basis is soda-lime glass; this is primarily a mixture of silicon
dioxide, calcium oxide (lime) and sodium oxide (soda). Its used for a range
of purposes, including bottles, containers, window panes and drinking
glasses. Its not, however, the only type of glass we can make.
Another type, which those who work in science laboratories will be familiar
with, is borosilicate glass. As well as silicon dioxide, this type of glass
contains boron trioxide. It has a greater durability, combined with greater
chemical and heat resistance, which leads to its use in laboratories, as
well as in cookware. Additionally, its used in flashlight lenses, allowing
a higher percentage of light through compared to plastic. A number of other
types of glass are also possible, such as lead glass, but are beyond the
scope of this post.
Coloured glass can actually be produced in a number of ways, but there are
three main methods. The first involves introducing transition metal or rare
earth metal oxides to the glass. This is usually achieved by the addition of
metal oxides to the glass. The metal ions absorb certain wavelengths of
light, varying depending on the metal, leading to the appearance of colour.
There
<http://www.compoundchem.com/2014/03/05/colours-of-transition-metal-ions-in-
aqueous-solution/> s more on what causes the colour of transition metal
ions here.
Another manner in which colour can be introduced is by formation of
colloidal particles. This simply means particles of a substance that are
suspended throughout the glass. These particles are often formed as the
result of treatment with heat, forming what are known as striking colours.
The colloidal particles scatter light of particular frequencies as it passes
through the glass, causing colouration. Examples of these colloidal particle
colourants include gold, which imparts a ruby red colour, and selenium,
which offer shades from pink to intense red.
The final main way in which colour can be introduced is merely via the
addition of already coloured particles to the glass. Examples of this type
of colouration include milk glass and smoked glass; milk glass is achieved
by adding tin oxide.
Coloured glass finds obvious usage for decorative purposes for instance,
stained glass windows take advantage of the colouring effect of metal ions.
The colour of glass can be more than just aesthetic, however. For example,
beer bottles are coloured green or brown to cut out specific wavelengths of
UV light which can otherwise contribute to beer spoilage and a skunky
flavour. Its also used in some chemical bottles for a similar purpose.
Theres a lot more to the colouration of glass than is covered in this brief
overview. If youre interested in learning about it in a little more detail,
check out the links below.
References & Further Reading
§ <http://www.springer.com/gp/book/9783540583578> The Properties of
Optical Glass Bach, Neuroth & others (paywall)
§ <http://www.rci.rutgers.edu/~glasseng/CourseLinks/ColorGlasEng.pdf>
Coloured Glass Rutgers University
§ <https://books.google.co.uk/books?id=BfyWUnv_-rEC&pg> Structural
Chemistry of Glasses K J Rao (partially available online)
§ <http://www.sha.org/bottle/colors.htm> Bottle/Glass Colours Historic
Glass Bottle Identification & Information
That embedded link to
http://www.compoundchem.com/2014/03/05/colours-of-transition-metal-ions-in-a
queous-solution/ has this second Infographic:
http://www.compoundchem.com/wp-content/uploads/2014/03/Transition-Metal-Ion-
Colours-Aqueous-Complexes.png
Enjoy,
Tony Patti
<http://www.glassblower.info> www.glassblower.info
<mailto:gaffer at glassblower.info> gaffer at glassblower.info
<http://www.glassblower.info/qr-code.html> QR Code for Tony Patti -
www.glassblower.info
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