Naturally Occurring Rubber Is What Color?
Natural rubber is created from latex fluids harvested from rubber trees and other plant species in various regions around the world. Latex is a milky colloidal fluid that, in its pure form, dries to form a white natural rubber—the pale color of latex gloves long used in the medical profession reflect this and early automobile tires were also a white tone in color.
Why, then, are so many rubber products today dark? Why are rubber stoppers, rubber feet on electronics, and rubber tires all charcoal black? While natural rubber is great for things like water resistance, it isn’t particularly durable. In fact, its default flexibility is actually a hindrance in applications, like tires, where durability is more important than extreme flexibility. In such cases, the rubber is vulcanized, a chemical process wherein the rubber is heated and sulfur, peroxide, or bisphenol is added to harden the rubber and increase its durability (carbon black was often used before World War II).
Image courtesy of Mohd Hafiz Noor Shams.