Latex or natural rubber begins with the milk from the Hevea brasiliensis, the Pará rubber tree, often simply called rubber tree. These trees are mostly grown in plantations in Southeast Asia (Sri Lanka, Malaysia), Africa and India. In 1929, Dunlopillo (then known as Dunlop Rubber Company) invented latex foam. This original process, called Dunlop or Standard process, is still widely used by most latex manufacturers worldwide.
This process was improved in the early 1950′s and is known as the Talalay process. There are only 3 manufacturers worldwide that use the Talalay process and because of the more complicated manufacturing process and expensive molds, the cost to produce Talalay latex is much higher.
How Dunlop or Standard Latex Is Made
A blend of natural or natural and synthetic latex with all of the necessary additives (vulcanizing and gelling agents, anti-oxidants) is mechanically frothed with the addition of soap and air. The foam is passed through a hose into molds as they pass on a conveyor. When the molds are filled to capacity, a lid seals the foam inside and the gelling agents act to solidify it.
The molds are then carried through a steam chamber at 230°F which triggers vulcanization or curing. As they emerge from the steam chamber, the molds open and the blocks are ready to be removed, washed and dried.
How Talalay Process Latex Is Made
The latex mix is prepared and filled into the mold similar to the Dunlop process. The mold is only partially filled, depending on the hardness of the block desired. The molds are aluminum and are fitted with a large number of pins – almost 20,000 each in the lid and pan. The pins serve the dual purpose of transferring heat to the center of the block as foam rubber is a poor conductor of heat, and of creating “pinholes” which later help it to dry.
The molds are fitted with a rubber gasket seal around the perimeter and contain internal hollow channels through which glycol/water heat transfer liquid can flow.
After the mold is partially filled with liquid foam, closed and cooled, a vacuum expands the foam to its full potential. A secondary internal semi-permeable paper gasket removes excess air from the mold and the foam is frozen to -22°F. Carbon dioxide gas is then passed through the frozen matrix, which causes the foam to “set” or “gel” further. At this moment, the individual air bubles interconnect.
Once the gelling is complete, the mold is slowly heated to 230°F and held there for a few minutes. The heat vulcanizes or cures the rubber, which gives it the normal resilient properties. The products are removed from the molds, submerged in water to remove residual soaps, etc., dried and inspected.
The Advantages Of Each Process
The best way we like to describe the difference in the feel between the two types of latex is Talalay is like angel food cake and Dunlop is like pound cake. The uniform, open cell structure of Talalay latex provides a consistent feel, superior resilience and durability. Because of the pin structure of the unique mold, Talalay latex is springier than Standard or Dunlop process latex. The interconnecting cell structure of Talalay latex also enhances ventilation and breathability, which means that body heat and moisture are drawn quickly through the mattress. This is why Talalay latex is preferred as the top layer and sometimes the middle layer of a latex mattress.
Standard or Dunlop latex produces a firmer mattress and can be slightly inconsistent from batch to batch. Because there is no freezing process, the pores are isolated, which creates a denser, less springy product. Dunlop latex is best suited as a core or bottom layer of a mattress but an all-Dunlop mattress works well for those that prefer a firmer or minimalistic feel in their mattress.
What About Latex Allergies?
Sometimes people is our store say they have a latex allergy or are concerned about having a reaction to latex. Actually, there is no such thing as a latex allergy – what it really is a allergic reaction to free proteins in the latex.
Washing latex mattress cores removes most of the free protein which can cause an allergic reaction to a small percentage of consumers. Unwashed latex mattress cores have been tested to have up to 773 units of protein per gram, while washed latex cores have been tested at 11.8 units of protein per gram, a 98.5% reduction in protein. Remember that protein is a touch-allergy, meaning that the skin must come into contact with it for a reaction to occur (a very small percentage of chemically-sensitive people can react to the smell of latex). A latex glove, the source of most allergic latex reactions, is around 50 units of protein per gram. Prolonged exposure to latex, wearing latex gloves for example, creates heat and carries the protein through the pores.
Not every manufacturer washes any or all of their latex products and there are no regulations for the amount of safe proteins in bedding products in the USA. All of the well-established reputable major manufacturers of latex mattresses know how their latex is processed and will be able to tell you how their latex is washed. The main concern are the many online stores that out-source their mattresses and have no knowledge or control of how the latex cores are processed.
How Can You Tell If A Latex Mattress Is Made From Synthetic Or Natural Latex?
Synthetic latex is made from petroleum-based chemicals and has a similar molecular structure as natural latex. The differences is that it lacks the proteins that can cause touch-allergic reactions in some people. It is also lighter in weight – the natural latex mattress core is 20% heavier than a synthetic mattress core of similar size and hardness.
The challenge for mattress shoppers is that it is perfectly legal and very common for mattress manufacturers to state that their mattress is made from “natural latex” when in fact it is mostly made from petrol-chemical based synthetic latex. In fact, IKEA has sold a “natural latex” mattress but has the integrity to state on their website that it is 85% synthetic latex.
Here are two ways to tell if a mattress is made from synthetic or natural latex. First, look at the law tag attached to the mattress and you might be able to see if and how much percentage of synthetic latex the mattress is made from. Second is the price – the lower the price, the more synthetic material has been used. This is also why a Certified Organic Latex mattress will cost more than a “Natural Latex” mattress as the mattress has a third-party organization that has traced the source and production of the materials used and tested the product for its purity.