Mattress Upholstery and Foam Beds
Between the springs and the mattress upholstery over the spring unit is placed a pad called an insulator pad or mesh. This prevents the upholstery from sinking into the coils, making dimples in the mattress. These are usually made with sisal,synthetic fibers, resin bonded synthetic pads, rubberized curled mesh or propylene netting.
UPHOLSTERY   The combination of products that are placed over the insulator to provide the mattresses feel and also determine the life of the mattress. We used to worry about spring life but in todays mattresses it is this layer that will wear out first.There are many types of foams used in combinations to create the upholstery layer. Polyurethane, visco elastic(memory foam),latex,organic or man made fibers are put into different combinations of thickness,position,number of layers to create the mattresses feel and longevity.

POLYURETHANE FOAMS are the most commonly used. It is a network of tiny interlocking elastic plastic struts and cavities that form cell structure. Regular polyurethane has a consistent,fine cell structure. This type of foam is found in most inexpensive bedding. A ratio of 2.2 is the lowest you should buy if you want the bed to have any reasonable comfort life. Hi performance foams are characterized by their course,random sized cells. It usually has a support factor(ratio: the amount of pounds it takes to compress the foam to 65%(ifd) of it's height divided by the ;pounds it will take to compress it to 25%(ifd) of it's height) the most common ratio is 2.4 in these types of foams. Regular foam cells compress at the same rate. Hi performance foams,because the cell size and cavity space are random some cells collapse while others don't, provide buoyant support. It allows a cradling ;with higher support at the same time. There are some hi performance foams that approach the performance of latex (found in upper models of King Koil or the Laura Ashley series. The amount and placement of hi density foam will determine how long the mattress will stay comfortable. In todays no flip mattress, having only one upholstery side, the types and grade of the foam is probably more important than the spring set to the length of time you can keep using it comfortably.

VISCO ELASTIC Memory foam is a foam that is the direct result of space age technology. Developed in the 1960's by NASA,but never used to protect astronauts from g forces during takeoffs and reentry. Unlike polyurethane and latex that are quick recovery foams (giving a bouncy feel) visco is a slow recovery foam leaving a low pressure surface offering a luxurious feel with low stress support. Originally these foams were activated by body heat and are heat sensitive thereby creating a very warm surface.the fact that it recovers slowly sometimes makes it harder to roll over in the bed. Tempupedic is the largest marketer of this type of bedding. Beware there are many manufacturers of memory foam beds Dormia,Sealy,Simmons and Tempurpedic all use 5.3 ratio foam or better. Less than this ratio has proven to wear out quickly. A new type of memory foam is hitting the market called cool foam reacting the same as the older type but isn't heat sensitive thereby eliminating one of the major negatives of the better known product. The heat problem can also be changed with lyosol covers and aerator pads. Note: the description here applys to an all foam bed not as layers in a spring bed. In a spring bed the ratio can and will be lower and because the memory foam doesn't have to support and be the primary body shaper, it can be placed away from the surface to offset the heat problem.

LATEX FOAMS-There are three major types of latex: Dunlop and Talalay are both natural methods of production. Sceintists have developed a synthetic latex. All of these are used to make both mattresses and padding layers. Natural latex comes from the sap of a rubber tree(40% of the milk from the tree is latex  and must be extracted). The difference between dunlop and talalay is in how it is manufactured. Dunlap is poured into an open mould and during the curing some of the particles can settle to the bottom, making it less consistent and generally harder. Talalay is poured into a closed vat, the air is removed and the mixture is frozen, curing as it melts making it  more consistent. This allows the manufacture to have a softer feeling surface without loosing strength. Synthetic latex(styreen butadiene rubber) is less expensive to produce and while not as good, has many of the advantages of natural latex.This foam gives the same benefit as memory foam without memory foams problems. it generally will out last memory foam by 133%.Warnings:;Make sure the latex was washed at least 5 times. Many people have a latex allergy, In most cases it is not the actually the latex but the enzymes and additives that causes the allergy. The washing removes these but one or two washings aren't enough.;Exotic sales pitches like European or Asian sound good but tests have shown the following
Loss of height under compression
100% talalay
loss of ild(impact test)
( these are approximate figures)
Pure latex can contain 80% synthetic latex
Natural latex can contain 20% synthetic (this seems to work the best)
Only 100% natural latex is all natural (second best)
Clean and less clean

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Foams in mattress Upholstery and in foam mattresses have the same descriptions when relating to

Mattress Construction

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Memory Foam Mattress