Material

Memory Foam

What it is

Memory foam is polyurethane foam modified to be viscoelastic, meaning it deforms slowly under load and returns slowly when the load comes off. That delay is the entire product. It shows up on this site in two very different forms: solid slabs cut for toppers, and cross-cut or shredded pieces packed into pillow shells where the fill can be added or taken out.

How it is made

Polyol and isocyanate are reacted with additives that control cell structure and the speed of recovery. Gel infusion mixes a gel phase into the foam before it cures. Ventilation means holes are cut through the finished slab. Both appear constantly on these listings and both are visible in the product: you can see the gel color and you can see the holes.

When it is wet

Badly. An open-cell foam slab soaks up many times its own weight in water and will not release it in any reasonable time, and the weight of the trapped water tears the cell structure apart while it is being handled. This is the concrete reason foam is not machine washable, and it applies to shredded fill as well as to slabs. Spot clean the foam, wash the cover, and follow the manufacturer label over anything written here.

When it is hot

Dense foam with small cells does not move air, and body heat has nowhere to go but into the foam. Gel infusion and ventilation holes are the two answers the industry has, and they are real design decisions rather than pure marketing, but neither converts a foam slab into an airy fabric. Shredded fill moves considerably more air than a solid slab because the gaps between pieces are air.

After fifty washes

The question does not apply to the foam, because the foam has not been washed fifty times and must not be. What ages instead is the cover, which goes through the machine on its own, and the foam itself, which loses recovery speed and eventually keeps an impression. Shredded fill breaks down at the edges of the pieces and the pillow slowly gets lower.