|The Secret of Everyday Things|
|by Jean Henri Fabre|
|Fascinating conversations with Uncle Paul reveal the mysteries behind the dyeing and weaving of cloth, the lighting and heating of homes, the processing involved in bringing oil, coffee, tea, spices, and other foodstuffs to the table, and the power of water in all its manifestations. Excellent as follow-on to The Story Book of Science. Ages 11-14 |
NCE upon a time, so the story goes, some sailors
overtaken by bad weather landed on a desert shore and
lighted a big fire to dry and warm themselves and pass
the night. There being no wood on this sandy coast,
they made their fire of dry seaweeds and grass. The
furious wind caused their fire to burn fiercely, and,
behold, the next morning the sailors were greatly
astonished to find in the midst of the ashes sundry
lumps of a substance as hard as stone but as
transparent as ice. If they had seen this substance at
the water's edge, and in winter, they would certainly
have taken it for ice, but, raking it out from under
the ashes, they could not escape the conclusion that it
was something else."
"And what was it?" asked Claire.
"It was glass, that precious substance that to-day
gives us our window-panes, which enable us to keep our
houses warm without excluding the daylight. The sailors
scrutinized closely the deposit left after their fire
had burned out, and they perceived that the great heat
had caused a part of the ashes to fuse with the sand of
the soil and thus produce the transparent substance in
question. It was thus that glass-making was
"Was that long ago?" Jules inquired.
 "This discovery, one of the most important ever made,
dates so far back that only a very vague record of it
has been preserved, and this record is probably a
mixture of fact and fable. But whether it be fact or
fable, the story teaches us at least one thing: sand
melted with ashes produces glass. Now, what can the
substance be that imparts to ashes the property of thus
transforming the sand? What is there in ashes of such a
potent nature as to bring about this wonderful change?"
"There is soda," Marie suggested, "that same soda that
turns oil or tallow into soap."
"It was in fact the soda from the marine plants burned
by the sailors that had brought about the melting of
the sand and the formation of lumps of glass. Potash,
which closely resembles soda in all its properties,
acts in the same way when it is heated to a high
temperature with sand. In both cases the result of the
fusion is glass, more or less colored, finer or
coarser, according to the purity of the materials used.
The fine and perfectly colorless glass of our goblets,
decanters, and flasks is obtained from potash and very
white sand; window-glass, which is very slightly green,
at least on the edge, is made of soda and pure sand;
common bottle-glass, dark green in color, or nearly
black, is made of very impure sand and ordinary ashes.
"The manufacture of window-glass is a very curious
operation. In a furnace heated to a very high
temperature are large earthen pots or crucibles filled
with a mixture of soda and sand. When these two
substances are thoroughly melted together the result
 is a mass of glass, red-hot and running like water.
Each crucible is removed by a workman and his
assistant, standing on a platform in front of an
opening through which the crucible is withdrawn. This
workman is called the blower."
"Why blower?" asked Jules. "Does he blow?"
"Indeed he does, and vigorously, as you will see. His
tool is an iron rod or tube with one end cased in wood
to enable him to handle the metal implement without
burning himself. The assistant heats the other end by
passing it through the opening in the furnace, and then
plunges it into the crucible. In this way he gathers up
a certain amount of paste-like glass, which he molds
into globular form by turning it around again and again
on a block of wet wood. That done, he again heats the
glass at the furnace opening, softens it, and passes
the rod to the workman, the glass-blower.
"The latter first blows gently into the tube, and the
mass of glass becomes inflated into a bubble exactly as
soap-suds would do at the end of a straw."
"I can make beautiful soap-bubbles by blowing with a
straw," said Emile. "Does the workman do it like that?"
"Yes, just like that. He blows through his tube into
the mass of glass which, flexible and soft as long as
it remains red-hot, swells into a bladder. Then the
tube is raised aloft and the workman blows the glass
above his head. The bladder becomes flattened a little
by its own weight, at the same tie gaining in width.
The blower lowers the tube again and swings it to and
fro like the pendulum of a clock,
 every now and then resuming his blowing with greater
force. By the action of its own weight, which lengthens
it, and the blowing, which distends it, the mass of
glass finally assumes the shape of a cylinder.
"The completed cylinder ends in a round cap which must
be got rid of. To accomplish this the end of the
cylinder is held near the opening of the furnace to
soften it, after which the top of the cap is punctured
with a pointed iron. By swinging the tube this puncture
becomes enlarged and the cap disappears. The cylinder,
hardened now although still very hot, is next placed on
a wooden frame containing a number of grooves or
gutters for receiving the cylinders. With a cold iron
the workman touches the glass where it adheres to the
tube, and by this simple contact a break occurs along
the line thus suddenly chilled, leaving the cylinder
entirely free from the tube.
"Notice, children, the clever device adopted by the
workman for detaching the glass from the tube without
shattering it. He merely touches the very hot glass
with a cold iron, and that suffices to produce a clean
break all along the line touched. Glass possesses this
curious property of not being able to withstand a
sudden change in temperature without breaking. Chilled
suddenly, it breaks; heated suddenly, again it breaks.
That is a warning to you when you wash drinking-glasses
or other glass objects. Beware of hot water if these
objects are cold, and of cold water if they are hot;
otherwise you run the risk of breaking them instantly.
When the cold
 or the heat acts only along a predetermined line, it is
on that line, suddenly chilled or heated, that the
rupture occurs. That is how, without the slightest
difficulty, the workman separates the glass cylinder
from the iron tube to which it adheres.
"This done, the next thing is to remove the cap that
still terminates one end of the cylinder. To do this
the workman encircles this cap with a band of very hot
glass, and then touches with a cold iron the line thus
reheated. Instantly a circular rupture detaches the
cap. Thus there is left on the frame a glass muff open
at both ends. To split this muff the workman draws
lengthwise, from one end to the other, a red-hot iron
point, and then touches the hot line with a wet finger.
A cracking follows, and the muff splits open. It is
next taken to a furnace where, after being softened
sufficiently, it is laid open and flattened out with an
iron rule on a cast-iron plate. The final result is a
large sheet of glass which the glazier will cut later
with a diamond point into panes of any desired size."
"That is a very curious operation you have just told us
about, Uncle Paul," said Claire. "For my part, I should
never have suspected that a pane of glass, so perfectly
flat as it is, was first a glass ball blown out like a
"And how are bottles made?" asked Jules.
"For bottles glass is both blown and molded. The tube,
laden by the assistant with the proper amount of melted
glass, is passed to the blower, who gives to the
vitreous mass the shape of an egg ending in a neck. The
piece is then resoftened in the
fur-  nace and put into an iron mold. By energetic blowing
the workman inflates the glass and makes it exactly
fill the mold. This operation leaves the bottom of the
bottle still flat, but by pressure with the point of a
sheet-iron blade this bottom is driven up inside and
shaped like a cone. A band of melted glass applied to
the narrowed opening of the piece gives the neck of the
bottle. The seal that some bottles bear, for example
where the word liter is inscribed, is made by attaching
a small disk of glass while it is still soft, and
stamping it with a mold made of iron suitably
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