Other Considerations

Edges have long been a part of spring mattresses because they are needed to hold the mattress together. The edging has been justified by explaining that it keeps you from sliding off when sitting on the side of the bed. My take on this is that chairs and couches don’t have edges, why should beds. The edging makes the usable part of the bed smaller. Maybe the edge keeps some people from falling out of the bed. I have seen commercial “latex” mattresses that have a polyurethane foam edging. This makes a 20 year mattress into a 10 year mattress with all of the negatives associated with using polyurethane foam. It is possible to put a firmer latex foam on the sides of a regular latex core, but I would not recommend it.

A sag factor > 3 gives an ideal sleeping comfort. To feel really comfortable, a mattress core firstly feels soft and shows increasing resistance as the core is further depressed. The quality "to react as equally as possible to a pressure or a load" is called the sag factor. This sag factor is presented through the ISO 2439 standard as the ratio of 65% ILD (indentation load deflection) to 25%. The higher this index, the better the foam supports the body equally. The sag factor for regular polyurethane foams is about 2 and for the more resilient HR-foams (High Resilient) about 3. Latex foam performs obviously better with a sag factor up to 4!

Cheap imitations are a problem in mattress too.

I have heard of memory foam mattresses where there are instructions to break in the mattress by walking on it for 15 minutes each night before you go to bed for the first week. This manufacturer did not run the finished mattress through a crusher to soften the cell structure before shipping the core.

There are only a few latex core manufacturers in the West (one in the USA) and they all produce quality (though different) products. Recently China has begun shipping latex cores — of varying or unknown quality.

Varying firmness along the length of a mattress seems like a good idea. Unfortunately, no one can take my measurements and build the perfect mattress for my size, weight, and sleeping patterns. Besides, putting more support where I am heavier seems like the wrong way around. You want to spread out the support so that the hips and back are supported equally.

Select comfort beds use a pump and air mattress inside a polyurethane foam shell. This is one of the few good ways that you can change the firmness of your bed after you bring it home. Some people complain about the air pump going off in the middle of the night, but most don’t. After a few days of changing the pressure the sleeper will typically keep the same firmness setting for the life of the mattress.

Different firmness on the two sides of the bed is a feature of the select comfort beds (there is often an uncomfortable transition in the center of the bed). Additionally, custom made foam mattresses can have different firmness for each partner. The mattress thickness should be the same on both sides, but the firmness of the support layers can be varied to individual taste.

Electro-magnetic fields (EMF) are of concern to some people. Metal attracts electric fields and so spring mattressess and box springs tend to concentrate these fields right through anyone lying on the bed. Although there is no proof that these fields are harmful, if you want to reduce this potential risk, avoid mattresses and foundations that contain metal.