Real-Life Communication
Glass blowers who mix their own glass need a good understanding
of chemistry.
You're a glass blower for a commercial studio that markets
fine, hand-blown glass pieces. As the senior glass blower and artist, you
are invited to a party to launch the new line of hand-blown crystal for the
company.
The pieces are beautiful. Teal and red glass is interwoven
in the body of the vase. At the party, a reporter comes up and asks if the
vases were difficult to make. You grab a manual on glass-making and hand it
to him.
The journalist blinks a couple of times and says it's all too
much. All he needs is for you to tell him in simple language how you produced
these pieces.
Below are some excerpts from the manual. Read the information,
and summarize the key points in a paragraph or two. Write in a conversational
manner, as this will make it easier for your listener to understand.
"Colors
in glass are created by combining certain chemicals that produce a given color
in a given set of circumstances. One important factor in producing color in
glass is controlling the atmosphere (a lack of oxygen). Some colors require
an oxidizing atmosphere (oxygen present).
"The chemical compound that
is used to control the oxygen in the atmosphere of a furnace is sodium nitrate
(NaNO3), which yields O2 during reaction. The problem
that arises when altering the sodium nitrate to control the atmosphere is
that the sodium content of the glass changes also. Therefore, the sodium content
must be adjusted elsewhere in the batch. The adjustment is made to the soda
ash (Na2CO3 or sodium carbonate).
"The mass of
the two compounds is different and they contain a different number of sodium
ions, therefore the proper amount of soda ash must be calculated to maintain
a homogenous composition between glasses of different colors.
"This
will ensure that the coefficient of expansion (COE) is equal for different
colors of glass, so that if the different color glasses are combined no stress
will be created between the colors during the annealing (cooling) process.
Stress would cause the glass to shatter."