All Natural Rubber Latex
Rubber tires, rubber stamps, rubber boots… these manufactured products are far from natural, right? Not as far as you may think.
Modern production of rubber starts with a small cut into the Hevea Brasiliensis Tree.
Latex Rubber Tapping
All natural rubber originates in the Hevea tree, and it starts its journey when the tree is “tapped”. Tapping is the process of using a sharp knife to shave off the thinnest possible layer from an intact section of bark. The cut must be neither too deep, nor too thick. Either will reduce the productive life of the tree.
In response to the small cut in its bark, the tree begins to heal its “wound” as the latex starts flowing. The tapper leaves a cup underneath the cut to collect the flowing latex. In ordinary circumstances, this latex will coagulate into a lump in the bottom of the cup, called ‘cup lump.’ If the plantation manager wants to make latex, then the tapper must add a stabilizing agent to the cup that will prevent the latex from coagulating. The tapper usually returns a few hours after the original cut is made to collect the cup filled with either a lump or latex.
It used to be that the Hevea tree had to be felled before the latex could be extracted, but since the technique of tapping was developed this is no longer necessary. The benefits of tapping include the extended life of the trees and plantations, more rubber produced from each tree, and lower cost (both monetarily to the end consumer and environmentally).
Latex Is Not Made From Sap
Latex is often described as the sap of the Hevea tree. This is not an accurate description. The sap runs deeper inside the tree, beneath the cambium. Latex runs in the latex ducts which are in a layer immediately outside the cambium. This highlights the skill of the tapper. If the cambium is cut, then the tree is damaged, because the cambium is where all the growth takes place. Too much damage to the cambium, and the tree stops growing and stops making latex.
Processing Of Latex – Cup Lump or Liquid Concentrate
If solid rubber is required, the cup lump, together with tree lace (the remnants of the latex flow from the cut down to the cup) and other bits and pieces are collected together and processed. That processing involves quite a lot of heat, which destroys many (but not necessarily all) of the proteins. It ends up as solid rubber. Depending on the method of processing and the final purity of the material, the industry refers to it either as TSR (technically specified rubber), or sometimes sheet rubber.
When latex is required–which covers about 10 percent of all natural rubber produced–the material is gathered on the tapper’s return journey, poured into containers and delivered to a processing station where it is strained and concentrated. At no stage in the process is the latex heated. This means most of the proteins remain in the latex. More stabilizer is added and the latex goes into a centrifuge to remove some of the water, and increase the rubber content of the latex. After centrifuging, the material is known as latex concentrate, and contains roughly 60 percent solid rubber and 40 percent other stuff (water, proteins etc.).
