Natural latex (sometimes referred to as “botanical” latex) is produced by a number of plants – even, surprisingly, dandelions (the U.S. actually made rubber from dandelions during World War II when Far East sources were cut off). According to the US Department of Agriculture, virtually all commercial natural latex comes from one particular tree: Hevea brazilliensis, originally from the Amazon basin but now grown worldwide.
The trees produce latex sap as a defense against insects. It runs year-round, and tapping the tree does it no harm. Rubber trees are tapped in much the same way as are maple trees.
When first collected, the natural rubber is dilute, typically only about 30%. That’s why it’s run through a centrifuge to concentrate it to greater than 61.5% solids: 60% polymer rubber, and 1.5% natural proteins, phosphilipids, carbohydrates, and amino acids, all essential to the final product. Before mixing and curing, about 1% sulfur and sodium are added; without these additions the “cured” rubber will remain gooey.
Once concentrated, the syrup is thoroughly mixed – with air getting added, just like with whipped cream – then poured into molds. In most Asian countries, the molds are rigid – one mattress comes from one mold at a time – but some U.S. and Europe makers use continuous molds. In the continuous system, the cured foam rubber comes out about the same way rolled steel is produced, or float glass: endless streams that are then cut and stacked.
Now there are two terms you’ll see bandied about, and if you’re thinking of a latex mattress you ought to know a bit about them: Dunlop versus Talalay. Both methods use the exact same raw material, but differ in how it’s cured.
– Dunlop, named after the tire and rubber company, is cured with pressurized steam, then washed repeatedly to remove the allergy-inducing short proteins.
– Talalay, named after the Russian brothers who invented the process, is first chilled, then the mold is vacuum sealed. The rubber expands as it’s cured with steam, so the final product is lighter. It requires considerably more energy to manufacture. After curing, it’s also washed.
Contrary to what some folks claim, there is NO inherent superiority of Talalay over Dunlop. Talalay is more expensive, and is better suited for some applications but by no means all. At Santa Cruz Natural Mattress, we can make a mattress entirely from Dunlop, or entirely from Talalay, or – most often – we use both. We never use more Talalay than required because that unnecessarily increases costs.