Re: Latex vs Foam mattresses ?
Some contradictory and confusing info here, so I have done a bit of searching on the web and learned a bit.
Of course all foams that are not latex are synthetic, which is to say created (synthesized) chemically from petroleum. Foams that are sold as latex are not necessarily "natural", but can be 100% natural (i.e. made exclusively from the latex of the rubber tree), 100% synthetic, or a blend of the two. Since the synthetic "latex" is less expensive than the natural latex, suspect synthetic unless it says clearly that it is 100% natural latex (and even then be a little suspicious). Blends seem to be largely a way of selling synthetics, with a little natural latex added to make it appear more premium. There seems to be a consensus that the natural latex performs better than the synthetic version, and can claim to be greener (no petrochemicals).
All foams, including latex, offer a range of densities (not talking about weight). So just because you know the chemical type of foam used in your mattress doesn't mean you know how it will feel (e.g. not all 100% natural latex is the same density, and thus can vary a lot in comfort depending on your preference).
Weight is a different matter. The range of synthetic foams, not including memory or latex, ranges from approx 1.2 to 3 lbs/cu ft. At the other extreme is latex, at 5.6 lbs/cu ft. (I suspect in practice it is a bit lower depending how many, and how large, cylindrical holes are molded into it.) Memory foam is in between at typically 3.2-4.0 lbs/cu ft.
It seems natural latex will outlast any of the synthetic foams we are likely to buy, thus at least in part justifying its higher cost.