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."