Although 75 percent of today rubber products are made from
the synthetic rubber perfected during World War II, rubber
bands are still made from organic rubber because it offers
superior elasticity. Natural rubber comes from latex, a milky
fluid composed primarily of water with a smaller amount of
rubber and trace amounts of resin, protein, sugar, and mineral
matter. Most non-synthetic industrial latex derives from the
rubber tree (Hevea brasiliensis), but various equatorial trees,
shrubs, and vines also produce the substance.
Within the rubber tree, latex is found between the external
bark and the Cambium layer, through which the tree sap flows.
Distinct from the sap, latex serves as a protective agent,
seeping out of and sealing over wounds in the trees bark.
To tap the substance, rubber harvesters cut a shaped wedge
in the bark. They have to be careful to make their cuts at
a depth of between .25 and .5 inch (.635 and 1.2 centimeters)
in a mature tree (7 to 10 inches or 17.7 to 25.4 centimeters
in diameter), because they must reach the latex without cutting
into the sap vessels. They must also take care to tap each
tree in a slightly different place every time. At the end
of the nineteenth century botanist Henry Ridley began recommending
this measure, having noted that repeated tapping in the same
After being extruded, the rubber tubes are forced over aluminum
poles called mandrels and cured in large ovens. Finally, the
tubes are removed from the mandrels and fed into a cutting
machine that slices them into finished rubber bands. spot
swiftly killed rubber trees. After workers make a cut, latex
oozes out and collects in a container attached to the tree.
Tapping takes place every other day, and each tapping yields
about 2 ounces (56 grams) of the substance. After tapping,
the cut dries, and latex stops flowing in an hour or two.
