Mattress Materials: A Complete Guide

Springs have been used in mattresses since the 1870s, and they remain the most popular support system in the UK. But not all springs are created equal.

Open Coil (Bonnell) Springs

The oldest and simplest design. Open coil mattresses use a single interconnected wire frame, meaning all springs are linked together. When you press down on one area, the surrounding springs respond too.

Pros: Affordable, widely available, good airflow
Cons: Partner disturbance (movement transfers across the mattress), less targeted support, tends to sag faster
Typical count: 300-400 springs in a double mattress
Best for: Guest beds, children, budget-conscious buyers

Pocket Springs

Each spring is individually wrapped in its own fabric pocket, so it moves independently. This is the key advantage: pocket springs respond to your body shape without affecting the area next to you.

Pros: Excellent motion isolation, targeted support, longer lifespan
Cons: More expensive than open coil, heavier
Typical count: 800-2000+ in a double mattress
Best for: Couples, people with back pain, anyone wanting better support

Micro-Pocket Springs

Smaller diameter springs (often 2-3cm) used in addition to standard pocket springs. They are typically found in a comfort layer on top of the main spring unit, providing finer contouring to body curves.

Typical count: 2000-6000+ when combined with standard pocket springs
Best for: Premium mattresses, side sleepers who need pressure relief

Zoned Springs

A pocket spring system where the spring tension varies across the mattress surface. Typically firmer in the centre third (lumbar zone) and softer at the head and feet. This provides targeted support where your body needs it most.

Key Fact: Pocket springs move independently, eliminating partner disturbance. Spring count matters, but construction quality and wire gauge are equally important indicators of mattress quality.

Spring count is the most-quoted mattress specification, but it is also the most misunderstood.

The Basics

Spring count refers to the total number of springs in a standard king-size mattress (150cm x 200cm). Manufacturers sometimes quote counts for different sizes, so always check which size the number refers to.

Does Higher Always Mean Better?

Not necessarily. A mattress with 2000 pocket springs is not automatically better than one with 1000. What matters is the combination of spring count, wire gauge (thickness), spring height, and construction quality.

General guidelines:

• Under 600: Basic support, likely open coil
• 600-1000: Entry-level pocket sprung
• 1000-1500: Mid-range pocket sprung, good for most people
• 1500-2000: Premium pocket sprung with enhanced contouring
• 2000+: Typically includes micro-pocket comfort layers on top of standard pockets

Wire Gauge

Wire gauge measures the thickness of the spring wire. In the UK, it is measured using the Standard Wire Gauge (SWG) system. Lower numbers mean thicker wire and a firmer feel.

• 12-12.5 SWG: Very firm (orthopaedic mattresses)
• 13-13.5 SWG: Firm
• 14-14.5 SWG: Medium
• 15-16 SWG: Soft, responsive

Key Fact: Spring count is one factor among many. Wire gauge, spring height, and build quality all affect how a mattress performs. Always consider the full specification, not just the headline number.

Memory foam (viscoelastic polyurethane foam) was originally developed by NASA in the 1960s for aircraft seat cushioning. It became widely used in mattresses from the 1990s onwards.

How It Works

Memory foam responds to heat and pressure. When you lie on it, your body heat softens the foam, allowing it to conform closely to your shape. When you move away, it slowly returns to its original form - the characteristic 'memory' effect.

Pros

• Excellent pressure relief - distributes weight evenly, reducing pressure points
• Good motion isolation - movement does not transfer (ideal for couples)
• Available at all price points - from budget to luxury
• Hypoallergenic - resistant to dust mites

Cons

• Heat retention - traditional memory foam traps body heat. This is the most common complaint.
• Off-gassing - new memory foam can emit a chemical smell (VOCs) that dissipates within days to weeks
• Slow response - the sinking feeling can make it harder to change position
• Durability varies - cheaper foams may develop permanent impressions faster

The Heat Question: Our Position

Based on WantMattress testing data, traditional memory foam does sleep warmer than pocket sprung mattresses. However, modern variants have substantially improved thermal performance:

• Gel-infused memory foam - gel beads or layers absorb and distribute heat
• Open-cell memory foam - larger cell structure allows better airflow
• Copper/graphite-infused foam - conductive materials draw heat away from the body

If you are a hot sleeper, these modern variants are significantly better than traditional memory foam, though a pocket sprung mattress with natural fillings will still typically sleep cooler.

Foam Density

Density is measured in kg/m3 and indicates quality and durability:

• Below 40 kg/m3: Low density - softer, less durable, budget
• 40-60 kg/m3: Medium density - good balance of comfort and durability
• 60-85 kg/m3: High density - premium, most durable, best support

Key Fact: Traditional memory foam does sleep warmer, but gel-infused and open-cell variants have largely addressed this. Foam density (measured in kg/m3) is the best indicator of quality and durability.

Latex is a naturally resilient material derived from the sap of rubber trees (Hevea brasiliensis). It offers a distinctly different feel from memory foam - responsive and bouncy rather than slow-sinking.

Natural vs Synthetic Latex

• Natural latex (Dunlop or Talalay process): Made from rubber tree sap. Durable, hypoallergenic, naturally antimicrobial, breathable, and biodegradable. More expensive.
• Synthetic latex: Petroleum-based (styrene-butadiene rubber). Cheaper but less durable and less breathable. Often blended with natural latex.
• Dunlop process: Denser, heavier, firmer feel. The sap is poured into a mould in one go.
• Talalay process: Lighter, more consistent, softer feel. The mould is only partially filled, then vacuum-sealed and flash-frozen before curing.

Latex Pros and Cons

Pros: Naturally breathable (sleeps cooler than memory foam), very durable (15-20 year lifespan), responsive feel, good pressure relief, eco-friendly (natural versions)

Cons: Expensive, heavy, limited availability in the UK, may trigger latex allergies (rare)

Hybrid Mattresses

Hybrid mattresses combine a pocket spring base with foam or latex comfort layers on top. They aim to deliver the best of both worlds: the support and airflow of springs with the pressure relief of foam.

Typical Hybrid Structure

1. Top layer: Memory foam, latex, or gel foam (2-5cm) for pressure relief
2. Middle layer: Transition foam for gradual support change
3. Base layer: Pocket springs (typically 800-2000) for core support and airflow
4. Edge support: Reinforced perimeter springs or foam for sitting on bed edges

Hybrids have become the fastest-growing segment in the UK mattress market, particularly among bed-in-a-box brands.

Key Fact: Natural latex is one of the most durable mattress materials (15-20 years). Hybrid mattresses combine springs and foam for a balance of support, pressure relief, and airflow.

The UK has a long heritage of mattress craftsmanship using natural materials. While foam and springs dominate the mass market, natural fillings remain highly valued for their comfort, breathability, and durability.

Wool

British wool is one of the most versatile mattress materials. It naturally regulates temperature (absorbing up to 30% of its weight in moisture without feeling damp), is naturally flame-resistant (important for meeting UK safety standards), and provides excellent cushioning.

Wool is commonly used as a comfort layer in both pocket sprung and hybrid mattresses. It sleeps cooler than synthetic alternatives and is inherently hypoallergenic.

Cotton

Cotton is breathable, soft, and moisture-wicking. It is often used in mattress covers and as a comfort layer. Organic cotton (certified to GOTS standards) is grown without synthetic pesticides or fertilisers.

Horsehair

A traditional luxury filling found in high-end British mattresses. Horsehair is extremely breathable, resilient, and long-lasting. It is typically curled and used as an insulation layer between springs and comfort layers. Mattresses with horsehair often last decades.

Silk

Used in premium mattresses as a thin comfort layer. Silk is temperature-regulating and feels luxuriously smooth. It is typically blended with other fillings rather than used alone.

Bamboo and Tencel

Bamboo-derived viscose and Tencel (made from eucalyptus pulp) are increasingly popular in mattress covers and comfort layers. Both are moisture-wicking and breathable, though their environmental credentials depend on the manufacturing process.

Key Fact: Natural materials like wool, horsehair, and cotton offer superior breathability and temperature regulation compared to synthetic alternatives. The UK has a strong heritage in natural mattress craftsmanship.

Mattress certifications can be confusing. Here is what the key ones actually signify.

UK Safety: BS 7177

All mattresses sold in the UK must comply with British Standard BS 7177 for flammability. This is a legal requirement, not optional. The standard specifies that mattresses must resist ignition from a match-equivalent flame source. Many manufacturers meet this using inherently flame-resistant materials (like wool) rather than chemical flame retardants.

OEKO-TEX Standard 100

An independent testing and certification system for textiles. A product with OEKO-TEX certification has been tested for harmful substances including pesticides, heavy metals, formaldehyde, and certain flame retardants. It does not certify organic production - only that the finished product is free from harmful levels of specified chemicals.

CertiPUR-US

A certification specific to polyurethane foam. It verifies that the foam is made without certain harmful chemicals (ozone depleters, heavy metals, formaldehyde, certain phthalates) and meets emission standards for VOCs (volatile organic compounds). Most reputable foam mattress brands carry this certification.

GOTS (Global Organic Textile Standard)

The leading standard for organic textiles. A mattress with GOTS certification means at least 70% of its textile fibres are certified organic, and the entire supply chain has been audited for environmental and social criteria.

FSC (Forest Stewardship Council)

Relevant to latex mattresses. FSC certification ensures the rubber tree plantations are managed sustainably and responsibly.

Key Fact: BS 7177 fire safety is a legal requirement for all UK mattresses. OEKO-TEX certifies absence of harmful chemicals. CertiPUR applies to foam. GOTS certifies organic textiles.