Memory foam is a type of viscoelastic polyurethane foam. It is made by producing a flexible polyurethane foam with a formulation and cell structure that give it a slower response to pressure than many standard upholstery or support foams. That slower response is the feature people notice when the surface gradually follows the shape of the body and then returns after the pressure is removed.
The phrase can sound more mysterious than it is. Memory foam is not a complete mattress material on its own in most practical constructions. It is usually used as an upper comfort layer, with a firmer and deeper support foam underneath. Understanding that distinction helps when comparing a memory foam mattress, a topper and a made to measure layered mattress.
The short answer
Memory foam is mainly a specially formulated polyurethane foam. Manufacturers adjust the formulation and production process to control properties such as:
- how quickly the foam responds to pressure
- how slowly it recovers after pressure is removed
- the density and weight of the material
- the finished softness or firmness
- the openness of the cell structure
- how the foam responds to temperature
Different products can therefore carry the same general memory foam label while feeling noticeably different. The finished feel also depends on the thickness of the memory foam and the material supporting it.
What does viscoelastic mean?
The term viscoelastic describes the way memory foam combines two behaviours. It changes shape gradually under pressure, and it also has the ability to return towards its original form when the pressure is removed.
This is why pressing a hand into memory foam can leave a temporary impression. A faster recovery foam springs back almost immediately, while memory foam takes longer to recover. The speed varies by grade, temperature and product construction.
That response is useful in a mattress comfort layer because the surface can adapt more closely than a standard support foam. It does not remove the need for a stable base. A thin memory foam layer over an unsuitable or worn support core will simply follow the weakness underneath it.
Is memory foam the same as ordinary polyurethane foam?
Memory foam belongs to the wider polyurethane foam family, but it is not the same as every standard foam sheet. The term polyurethane covers a broad range of flexible and rigid materials with very different uses.
Within the All Foam range, the practical distinction is:
- Memory foam gives a slower, contouring response and is normally chosen for an upper comfort layer.
- Medium or high support foam responds more quickly and can form the main base of a mattress.
- Reflex foam has a resilient, quicker recovery feel and can be used where a more responsive construction is preferred.
Our guide to memory foam vs Reflex foam explains how those response characteristics affect a custom mattress build.
Why is memory foam normally used on top?
A mattress needs both comfort and support. Memory foam is useful near the sleeping surface because its slower response changes the initial feel of the bed. The deeper base has a different job: it provides most of the thickness, stability and structural support.
For example, the All Foam mattress range uses a memory foam comfort layer over a deeper support layer. The exact construction varies by model:
- Deep Sleeper Comfort combines a medium feel with a medium density support base.
- Deep Sleeper Back Care uses a firmer high density support base.
- Luxury Deep Sleeper uses a deeper Luxury Reflex support layer.
The important point is that a mattress should be judged as a complete construction. A thicker memory foam layer is not automatically better, and a high density material is not automatically firmer. Density, firmness, layer depth and the support underneath all need to be considered together.
What gives memory foam its slow response?
The finished behaviour comes from the foam formulation and internal cell structure. Air can move through the cells as the foam is compressed and recovers. The material also responds to pressure and temperature, which is why the same foam may feel firmer in a cooler room and more yielding after it has been in contact with the body.
Does colour tell you what memory foam contains?
No. Colour is not a reliable way to judge composition, density, firmness or quality. Foam can be naturally pale or deliberately coloured during production. A white, cream, blue or other coloured foam may still belong to a similar material family.
Use the product specification and linked technical data sheets rather than appearance alone.
Is all memory foam open cell?
Memory foam used for bedding is a cellular material, but descriptions such as open cell are applied differently by different sellers. The useful buying questions are more practical:
- What is the intended application?
- What thickness is supplied?
- What support layer sits underneath it?
- How quickly does it recover?
- Does the product page make clear fire and care information?
- Is the finished mattress suitable for the bed base?
Avoid assuming that a marketing phrase guarantees a particular temperature or comfort result. People experience mattress warmth and firmness differently, and the cover, room, bedding and bed base also affect the finished setup.
What is the difference between memory foam density and firmness?
Density describes how much material is present in a given volume of foam. Firmness describes how resistant the foam feels when compressed under a specified test. They are related to performance but they are not the same measurement.
A denser memory foam can still be formulated to feel relatively soft, while a lower density foam can be made to feel firmer. This is why a mattress should not be selected from density alone. Read our guide to foam density vs firmness for a fuller explanation.
What should support memory foam in a mattress?
A complete memory foam mattress normally needs a deeper support layer. The correct choice depends on the desired feel and total thickness.
A balanced construction generally keeps most of the mattress depth in the base. This helps prevent the upper comfort material from being asked to do a structural job it was not selected for. In the All Foam custom mattress builder, one, two and three layer options are restricted by the total thickness so the construction remains clear and usable.
For custom sizes:
- below 4 inches, one foam layer is available
- from 4 to 7 inches, one or two layers are available
- from 8 to 10 inches, one, two or three layers are available
The base support layer normally remains thicker than the upper layers combined, with the specific balanced 2 inch plus 2 inch option available for a 4 inch two layer construction.
Does memory foam contain springs?
Memory foam itself does not contain springs. A full foam mattress uses foam through the comfort and support sections. A hybrid mattress may place memory foam above a spring unit, but that is a different construction.
If you are comparing the two, use the complete product specification rather than assuming one type is universally better. Our foam mattress vs spring mattress guide explains the main differences in response, movement, support and care.
What should you check before buying memory foam?
Before ordering, check:
- the exact finished mattress size
- total mattress depth
- memory foam layer thickness
- support foam type and depth
- stated comfort level
- whether the cover is included
- delivery and warranty terms
- care instructions and suitable bed bases
A product page that only says memory foam without explaining the rest of the mattress gives you too little information. Compare the whole layer build and choose the feel that suits your preference rather than selecting the largest number of foam layers.
Memory foam in toppers and mattresses
A memory foam mattress topper is a separate layer placed over an existing mattress. It can alter surface comfort when the mattress remains supportive. It cannot repair a broken, deeply sagging or unstable mattress.
A memory foam mattress is a complete sleeping surface with its own support core. If the bed frame is an unusual size, a foam mattress cut to size can combine custom dimensions with an appropriate support and comfort construction.
What memory foam is made from
Memory foam is a specially formulated viscoelastic polyurethane foam designed to respond more gradually than standard support foam. Its value in a mattress comes from how it works with the layers below it, not from the material name alone.
Choose by comparing the total build, support base, comfort layer thickness, firmness description and exact dimensions. That gives a clearer picture of the finished mattress than colour, marketing labels or memory foam thickness considered in isolation.