Tip:
Highlight text to annotate it
X
You might not noticed, but road signs have undergone a subtle change in recent years
thanks to advances in technology. Today's signs are more reflective than ever. You can
actually read them in the dead of night even when the only source of illumination is your
car's headlights. The earliest road signs were crude--a stick in a ground or a heap
of stones--to mark the route. In the Roman Empire, stone posts were erected along roadsides
at regular interval indicating the distance to Rome. Centuries later stone marker system
gave way to wooden cross signs pointing in several directions at once.The international
system of road signs we know today came out of the first international road Congress held
in 1908. The process of manufacturing a road sign starts with the computer. The government
strictly regulates the specifics of the design and requires a certain degree of reflectivity.
The computer specialized software guides the machine to cut the design on a sheet of film.
Once the design is cut, workers carefully peel off and discard the pieces. What's left
is the film stencil of the design. In this case, a French stop sign.They inspect it for defects, then prepare a screen
of polyester fabric that they'll later use to print the sign. They start by printing
a thin layer of light sensitive emulsion. Once the emulsion dries, they adhere the film
stencil using vaccuum pressure to flatten it and get rid of any creases or air bubbles.
Then they expose the screen to an intense 6,000 Watt light for seven minutes; this activates
the elmusion on the lettering--area outside of the octagon--what's not shielded from the
light of the stencil. This exposed emulsion hardens, plugging the minute holes between
the screen's fibers. After rinsing, you see the result. Elsewhere in the factory, workers
cut the aluminum panels on the side which the sign will be printed. Using a punch press,
they round out the edges and make holes for the bolts that will later attach the sign
to the post. They stamp on the company name and year of manufacture for warantee purposes.
They immerse the panels in a chemical bath to remove grease and other residues. Then
they rinse off the panels and dip them in an acid solution that seals the metal to make
it withstand harsh weather. Next, they laminate the aluminum panels with a film containing
miniscule glass particles. This film will make the sign reflect in the dark when light
hits it. Then they cut the panel to the final shape. Now, they can finally print the sign.
The process they use is called "silk screening." Although the fabric screen as you saw earlier
isn't actual silk, it's polyester. The machine forces the ink down to the screen, on to the
panel. The ink penetrates through the open fiber holes of the octagon, printing the red
background of the stop sign, but it can't penetrate through the blocked fiber holes
of the lettering and the outside of the octagon, so those remain white. The freshly printed
signs pass through the dryer at about 150 degree Fahrenheit for five minutes. To produce
street signs, workers first laminate aluminum panels with reflective film for the background
color. Then [they'll] either silk screen the street names or apply self-adhesive reflective
lettering, but it's back to the silk screening process for printing multicolored signs. Workers
print them one color at a time with the drying cycle between colors. All the film stencils
are carefully stored for future use. The printed signs go into an oven for a final curing at
349 degree Fahrenheit, an hour for one color signs and a half hour for multicolored signs.
The ink is transparent enough not to block the reflective film underneath. Therefore,
the entire sign, not just the lettering, is highly reflective that maximizes the sign's
reflectibility, thereby minimizing the excuses drivers can come up with for not heading it.