Natural rubber is a versatile material used in countless products, from vehicle tires to medical gloves. Its unique properties, such as elasticity, durability, and water resistance, make it indispensable across many industries. The primary source of this material is latex, a milky fluid harvested from specific trees. This article explains how this raw material is extracted.
The Source: Rubber Trees
The main source of natural rubber is the Pará rubber tree, scientifically known as Hevea brasiliensis. This tree is native to the tropical rainforests of the Amazon basin and the Guianas in South America. It thrives in humid lowland tropical conditions, typically between 15°N and 10°S latitude, preferring temperatures around 26-28°C and annual rainfall between 2000-3000 mm.
Hevea brasiliensis is a fast-growing, medium to tall tree, reaching up to 25 meters in plantations and sometimes 40 meters in the wild. Within its bark, the tree possesses a specialized system of vessels, known as laticifers, which produce and store a white, sticky, colloidal fluid called latex.
The Tapping Process
The extraction of latex from the rubber tree is achieved through a precise method called rubber tapping. This process involves making a careful incision into the tree’s bark to access the latex-carrying vessels without harming the underlying growth layer, known as the cambium. Tapping typically begins when trees are approximately six years old and have reached a girth of at least 50 cm.
A specialized hooked knife is used to make a thin, half-spiral cut along the tree trunk. This incision runs from high-left to low-right, aligning with the natural angle of the latex vessels (2 to 7 degrees from vertical) to maximize severed vessels. The cut’s depth is carefully controlled, generally 1 to 2 millimeters, ensuring it is shallow enough to avoid damaging the cambium, which is important for bark regeneration and the tree’s continued health.
Latex accumulates within the laticiferous system under significant internal pressure, known as turgor pressure. When the tapping cut severs these vessels, this pressure expels the milky fluid. The flow rate is highest immediately after tapping and gradually diminishes as turgor pressure decreases and vessels begin to plug. Tapping is commonly performed in the early morning hours, before temperatures rise, when the tree’s internal pressure is highest, allowing for a longer and more consistent latex flow. Trees are usually tapped on alternate days or every third day to allow the bark to regenerate.
Latex Collection and Initial Handling
After the tapping incision is made, the flowing latex is directed into a collection vessel. Small cups, often made of plastic, metal, or traditional coconut shells, are attached to the tree just below the cut by a spout. The latex drips slowly into these cups over several hours, typically completing its flow within half a day. To maintain quality, harvesting is usually avoided on rainy days, which could dilute the sap.
Prompt collection of the latex is important to prevent premature coagulation, which can occur naturally within a few hours of extraction. Upon collection, the raw liquid latex (about 30-35% rubber) is transported to a central processing facility on the plantation. Here, immediate steps are taken to stabilize it. The most common method involves adding ammonia, which acts as a bactericide and raises the pH, preventing bacterial growth and maintaining the latex in a liquid, stable state for longer storage and transport. Other stabilization methods are also used. Some naturally coagulated latex, such as “cup lump” (latex that coagulates in the cup after collection) and “tree lace” (coagulated latex on the tapping cut), is also collected for different processing pathways into various grades of solid rubber.