Graphite foam in a mattress: what it is and whether it actually works

Graphite foam has started appearing on spec sheets next to the usual "gel" and "cooling" words. Unlike most of them, it is based on something real. Here is what it is, what it does, what it does not do, and where it belongs.

What it is

Memory foam with graphite, a form of carbon, mixed into the foam as a fine powder during manufacture. The foam is usually also made more open-celled than standard memory foam. It looks dark grey rather than the cream or white of ordinary foam.

Why graphite

Graphite conducts heat well, far better than polyurethane. Mixed through the foam, it gives heat a path to move away from your body and down into the mattress, instead of sitting in the top centimetre next to your skin. The open-cell structure lets air move through as well. So the two problems with memory foam, holding heat and blocking air, are both reduced.

What it does and does not do

Does: it lowers the temperature at the surface compared with standard memory foam of the same density, and the difference lasts through the night rather than fading after the first hour like gel beads or a cool-touch cover. Under a latex layer it works as a heat sink, pulling warmth down and away.

Does not: make memory foam cool. It is still memory foam: dense, moulding, and warmer than latex, wool or a bare spring unit. If graphite foam is the layer you lie on, you will be cooler than on ordinary memory foam and warmer than on latex.

Does not: do anything for a hot flush, night sweats or a hot room. Nothing in a mattress does. It stops the mattress adding to the problem.

Where it belongs in a build

Under something more breathable. The best use of graphite foam is as the second layer: latex or fibre on top for air and moisture, graphite foam beneath it to take heat downward and provide pressure relief, then an air-channel layer and springs to move the heat out. Used on top, it is the second-best cooling top layer after latex. Used under a thick quilted polyester cover, it is wasted.

Reading the spec

Graphite foam is still memory foam, so the same numbers matter: density (50 kg/m³ and up to last), and hardness. Ask what percentage of graphite is in the foam and whether it is open-cell; "graphite-infused" with no numbers is a colour, not a spec. Also ask what is on top of it and what the cover is made of, because those decide whether the graphite gets to do anything.

Alternatives that also work

• Latex on top: cooler than any memory foam, graphite or not.
• Wool and cotton in the top layers: they move moisture, which is half the problem for night sweats.
• An egg-box (convoluted) foam layer under the comfort layers: air channels that let heat leave.
• Springs with a vented border rather than a solid foam core.

Combine two or three of these and the mattress stops being the reason you are hot.

How we use it

In The Hot Flush the graphite open-cell memory foam is 3 cm of 55 kg/m³ foam under 3 cm of Talalay latex, over a convoluted layer and a sprung unit with an open-mesh border. It does the pressure relief and the heat sink; the latex does the touch.

The short version

• Graphite conducts heat away; open cells let air through. It is the one cooling foam with a mechanism behind it.
• It makes memory foam cooler, not cool.
• Best used under latex or fibre, not on top.
• Ask for density, graphite content and what is above it.