Natural Latex can be found in almost all plants and trees throughout the world. Mattresses and mattress toppers made of pure latex can be manufactured in two ways: Natural Rubber Latex, which is 100% pure "green" latex, and as a mix that also contains Styrene Butadiene Rubber which is a synthetic latex. There are not very many manufacturers of natural latex around the world but those that do manufacture latex use a process called the talalay process.
Now, the big decision for most people at this point is whether to go with 100% natural latex or to use the synthetic blend latex. I'll begin with the advantages and disadvantages of natural latex. First, natural latex is, well, just what it sounds like: 100% natural with only a few other natural curers and catalysts that are washed, aired or heated out of the final product. This leaves a chemical free, allergen free and almost odor free piece of foam that is both resilient to repeated usage and is naturally flame resistant. However, as with most things in nature, there is some inconsistency with natural latex.
The talalay process works well to distribute the cell structure evenly through the foam, but it can only do so much. There are still some inconsistencies with natural latex including different batches of foam resulting in different supportive properties, discolorations between different batches of foam and the simple fact that almost ALL foams do wear out at some point after years of use.
To make the next section a little easier to discuss, I will call the blend of natural latex and synthetic latex, Syntex. Syntex is another form of foam used in mattresses and toppers and is passed off simply as "latex foam". Syntex has the same properties of natural latex when it comes to support, firmness and quality, but it does excel in one two areas: consistency and life. The chemicals added during the manufacturing process allow for better dispersion, and thusly, better consistency throughout each individual piece of foam. This gives control over the feel and the density of the foam. These chemicals also cause a strong cell structure within the foam giving it increased durability and longer life without sacrificing comfort. On the downside these chemicals do irritate those sensitive to allergies and can leave a particular odor. Thankfully, the smell does fade over time.
Prices vary depending on whether one looks to a brand name latex mattress or whether they look at quality alternatives that have sprung up within the market the past few years. Happy hunting!