Springs
March 2026What are Cortec Springs?
We’ve been making mattresses here in the UK for over 25 years, and we’ve handled, tested, and dissected more spring systems than most people have had hot dinners. So when Cortec springs arrived in 2019, we were curious rather than impressed. Here is our honest assessment of what they are, what they claim to do, and why we believe the conversation around spring counts and spring types is missing something far more important: what sits above the springs.
What exactly is a Cortec Spring?
A Cortec spring is, at its core, a spun-bond synthetic pocket spring. If you have bought a mid-range mattress from a high street retailer in the last decade, you have almost certainly slept on spun-bond pocket springs. They are the industry standard for most mattresses sold in the UK. The spring wire is encased in a synthetic polymer-based covering, heat-sealed to form the individual pocket, and then joined together into rows to create the spring unit that sits beneath your upholstery layers.
What Harrison Spinks changed with Cortec is how those rows are bonded together. Rather than using adhesive glue to hold the pockets in formation, Cortec springs are heat-sealed, meaning the spun-bond material itself is melted and re-hardened to form a seal. The individual springs can then concertina together by folding their rows in. Think of a roll of sticky labels and how each one folds back onto the previous one or tears away cleanly. That is essentially the same physical principle at work in a Cortec spring unit.
Harrison Spinks also made the springs themselves slightly taller and thinner than a standard pocket spring, which they claim provides more compression travel and more points of contact between the spring and the sleeper. These are the three headline claims: glue-free construction, recyclability, and enhanced comfort through the elongated form factor.
The glue-free claim and why it matters less than you think
Let us be clear: removing glue from a spring unit is genuinely a good thing. Glue in any mattress component restricts movement and reduces the individual responsiveness of whatever it is bonding together. It is one of the primary reasons we have always been deeply sceptical of foam-in-a-box mattresses, where multiple layers of Foam are essentially glued into a fixed block. The Foam cannot breathe, cannot move independently, and the glue itself adds a layer of chemistry that serves nobody’s long-term interests.
So the Cortec approach is directionally correct. But it is worth noting that glue-free spring construction is not new. Calico-encased pocket springs, the type used in the highest-end mattresses made by Vispring, Savoir, and ourselves across our Artisan range, have always been stitched together by hand rather than glued. Our spring technicians sew each calico pocket spring row to the next using traditional methods refined over generations. There is no heat-sealing here, no polymers, no industrial process. Just Cotton calico fabric, steel wire, and skilled hands. Cortec has arrived at glue-free construction through innovation in synthetic materials. Calico Springs got there first, through craftsmanship.
What does calico actually mean, and why does it matter so much?
Calico is a plain-woven Cotton fabric, typically unbleached and undyed, that has been used to encase pocket springs in premium mattresses for well over a century. The reason it remains the material of choice at the top end of the market comes down to a combination of breathability, natural responsiveness, and longevity.
Calico Cotton breathes. Air moves through it naturally with every compression and extension of the spring, which is fundamental to temperature regulation in a mattress. Synthetic spun-bond casings, including the polymer fabric used around Cortec springs, are considerably less breathable. Over the course of a night, a mattress breathes thousands of times as sleepers move, turn, and shift position. That cumulative difference in airflow is the difference between a mattress that sleeps cool and one that gradually builds up warmth.
Calico Cotton also responds faster. The natural fibre has an inherent elasticity that allows it to compress and extend with the spring in a more fluid, reactive way. Synthetic spun-bond fabric is slightly slower to respond, which is why even the most enthusiastic descriptions of Cortec spring performance will always be compared against other synthetic-cased springs rather than against calico. Against calico, synthetic springs of any type simply cannot match the responsiveness.
Beyond breathability and responsiveness, calico springs have a significant structural advantage that rarely gets mentioned in product descriptions: they are fundamentally more stable. A hand-stitched calico spring unit holds its formation with genuine rigidity. The stitching creates firm lateral connections between the spring rows, resisting the sideways drift and distortion that can develop over years of use. This means the spring unit maintains its intended geometry over the long term, providing consistent support from the first night to the thousandth.
The spring count arms race, and why it is damaging your mattress
Nothing reveals the gap between marketing and reality in the mattress industry quite like the spring count debate. Over the last twenty years, retailers have driven an extraordinary inflation in spring counts, with numbers climbing from sensible figures of 1,000 to 1,500 springs through to the extraordinary claims of 10,000, 15,000, or even more springs in a single mattress.
Each leap in spring count is presented to the consumer as an unambiguous improvement. More springs, more support. More springs, more comfort. The logic seems intuitive. It is also largely wrong.
Here is the physical reality of mattress construction. A standard king-size mattress is roughly 150cm x 200cm and typically between 27cm and 35cm deep. Within that volume, you need to fit a spring unit, multiple layers of upholstery and fillings, a border, and the cover itself. The total depth is fixed. The total interior space is fixed. If the spring unit occupies more of that fixed space, something else must occupy less of it. That something else is almost always your upholstery.
The minimum number of full-size pocket springs you can physically fit into a king-size mattress is around 600. Most mid-range mattresses use 1,000. Premium single-layer spring units run to around 1,500-2,000. Beyond 2,000 full-size springs in a single layer, you have simply run out of room. Any spring count above that threshold requires either a second spring layer or much smaller springs.
Cortec springs, being elongated and thinner than standard pocket springs, allow more of them to be fitted into the same footprint. Harrison Spinks mattresses using Cortec technology regularly advertise spring counts of 3,000 to over 14,000. To achieve those numbers in a standard mattress depth, Cortec springs are combined with additional micro-spring layers. Each micro spring is a tiny, titanium-alloy pocket spring that acts primarily as a comfort layer rather than a structural support layer. There is nothing inherently wrong with micro springs, but they are not the same thing as full-scale structural pocket springs, and using them to inflate headline spring counts is a marketing tactic rather than a technical advancement.
More importantly, those inflated spring counts have a direct cost. Not a financial one, but a physical one. Every centimetre of mattress depth given to additional spring layers is a centimetre taken away from natural fibre upholstery. And it is the upholstery, not the spring unit, that determines how your mattress actually feels to sleep on, how well it regulates your temperature, how it cushions pressure points, and how it holds up over a decade of regular use.
Why upholstery is where your money should be going
The spring unit in a well-made mattress is an engineering foundation. It does its job quietly and consistently for many years, provided it is built properly in the first place. The calico springs in our Artisan range will comfortably outlast a decade of regular use without meaningful deterioration. The same holds broadly true of any quality pocket-spring unit, including well-constructed synthetic ones.
What varies dramatically between mattresses in the same price bracket is the upholstery sitting above that spring unit. Natural fibres like Wool, Horsehair, Horsetail, Cotton, Cashmere, and Silk behave entirely differently from polyester pads, synthetic foams, and man-made comfort layers. They breathe, they respond to body heat, they compress and recover over the nightly sleep cycle, and they last far longer without the kind of permanent compression that causes the familiar dips and body impressions of a worn-out mattress.
When you see a mattress with an enormous spring count, ask yourself what the upholstery specification is.
Suppose the retailer can tell you the spring count to the nearest hundred but cannot tell you the GSM (grams per square metre) weight of each upholstery layer, which tells you something important about where the manufacturer has chosen to invest. We publish the full GSM specification of every mattress we make, precisely because we believe the upholstery is where the real story lies.
Cortec springs and the no-turn question
The original Cortec mattress range from Harrison Spinks was launched as a collection of four no-turn mattresses. This is worth pausing on, because the no-turn question is central to understanding the longevity trade-offs in modern mattress design.
A one-sided mattresshash all its upholstery on one side only. You sleep on the same surface every night, which means that surface bears 100% of the wear, compression, and loading that your mattress experiences over its lifetime. The argument for no-turn construction is convenience. The reality, based on years of customer feedback and our own testing, is that one-sided mattresses compress and develop body impressions significantly faster than their two-sided, turnable equivalents.
Our mattresses are all two-sided. You turn them periodically, distributing the wear evenly between both sleep surfaces and effectively doubling the working life of every fibre and every spring in the mattress. When someone asks us whether Cortec springs are worth the premium, part of our answer always comes back to this: if those Cortec springs are housed in a one-sided mattress, a portion of their potential longevity will never be realised.
Spunbond Pocket Springs are cheaper to produce using synthetic encasing
Calico Pocket Spring offers the ultimate in flexibility & breathability
The recyclability argument: real progress, real caveats
The claim that Cortec springs are fully recyclable is genuine and worth acknowledging. A spring unit made entirely from two materials, without adhesives, is theoretically far simpler to dismantle and recycle at the end of life than a conventional glued unit. This is meaningful progress, and Harrison Spinks deserves credit for it.
The wider context, however, is sobering. Around 7 million mattresses reach the end of their lives in the UK every year, and the vast majority end up in landfill. Local councils across the country have been chronically slow to develop mattress recycling infrastructure, and the handful of specialist recyclers operating nationally are nowhere near sufficient for the volume of material being disposed of. Some retailers offer collection and recycling schemes, but the provenance of the recycling is not always what it claims to be. We have heard credible accounts that mattresses collected under recycling programmes have ended up at mixed-waste incineration facilities.
The best contribution any mattress can make to this problem is simply to last longer. A mattress that serves a household for fifteen years rather than seven represents a substantially smaller environmental footprint, regardless of how its spring unit is constructed. Two-sided construction, quality natural fibre upholstery, and proper maintenance are the factors that determine how long a mattress lasts.
Our honest verdict on Cortec springs
Cortec springs are a competent synthetic pocket spring with some genuine improvements over standard spun-bond construction. The removal of glue is positive. The recyclability is positive. The slightly elongated form factor provides marginally more compression travel. When compared to other synthetic pocket springs, they perform respectably.
But they are still synthetic. They are still less breathable than calico. They are still slightly slower to respond than a calico spring. And they are typically deployed in mattress constructions that use inflated spring counts as a headline selling point, which, as we have explained, tends to come at the expense of the natural fibre upholstery layers that make the real difference to comfort, temperature regulation, and long-term performance.
If your choice is between a Cortec-sprung mattress and a standard glued spun-bond mattress at a similar price, Cortec is the better option. If your choice is between a Cortec-sprung mattress and a hand-stitched calico pocket-spring mattress with serious natural-fibre upholstery, you are comparing entirely different philosophies, and the calico mattress wins on almost every technical metric that matters for long-term sleep quality.
Two mattresses worth considering instead
Rather than leaving you with a verdict and nothing to do with it, we want to suggest two mattresses from our own range that we believe represent what this article is really about: spring quality, upholstery depth, and honest transparency in specifications. Both are two-sided, both use calico-encased pocket springs, and both give you the full GSM breakdown by layer upfront.
Origins Natural Comfort: the honest entry point into natural fibre sleep
The Origins Natural Comfort sits at the point in our range where synthetic upholstery gives way entirely to natural fibres, and the difference is immediately apparent to anyone who has slept on a conventional synthetic-filled mattress.
The spring unit uses 1,000 spunbonded pocket springs. Above those springs, the upholstery builds up through 600gsm of layered Cotton rebound pad, 500gsm of British Wool, a further 600gsm of rebound polycotton, a second 600gsm polycotton layer, and a 250gsm blend of Wool, Cashmere, Silk, and Cotton. Total upholstery weight runs to 2,550gsm across the full mattress depth of 30 to 33cm.
The inclusion of Cashmere and Silk at this price point is unusual in the UK market. Most manufacturers at this price bracket are still working with synthetic fibres. The Cashmere, in particular, provides a distinctive, immediate softness and warmth response that no polyester pad can replicate. The British Wool layers beneath provide the foundation of temperature regulation, compressing under load and recovering overnight to maintain loft and breathability across both sleep surfaces.
At £1,300 for a king-size, the Origins Natural Comfort represents exceptional value for a genuinely natural fibre mattress with calico springs and two-sided construction.
Artisan Bespoke 004: when you want the full specification
The Artisan Bespoke 004 is where our commitment to specification transparency becomes genuinely instructive. This mattress uses 1,600 calico-encased pocket springs in a 49mm format at 1.4mm gauge, hand-stitched throughout. The upholstery above those springs is built in layers that most manufacturers at twice the price point would struggle to match: 1,200gsm of blended British Fleece Wool and Cotton, a hairproof cambric cover, 200gsm of soft Bamboo, 1,200gsm of pure Horsetail, and 1,000gsm of bonded British Fleece Wool and Cotton. Total upholstery weight is 3,600gsm across a mattress depth of 27 to 30cm.
Horsetail is worth explaining here because it is a fibre that appears at the higher end of our range and often surprises people. Pure Horsetail is one of the most resilient and springy natural fibres used in mattress construction. Unlike Wool, which compresses gradually over time, Horsetail has an extraordinary ability to retain its loft and bounce back after loading.
It is this property that gives the Artisan Bespoke 004 its characteristic medium feel and its exceptional durability. The two sleep surfaces of this mattress, each containing a full complement of Horsetail and Wool upholstery, will maintain their comfort characteristics for well over a decade with proper turning and care.
The 1,600 spring count is not a marketing number inflated by micro-spring layers or stacked synthetic units. Each of those 1,600 springs is a full-size, individually hand-stitched calico pocket spring providing genuine structural support. The count is what it is, and the specification is what it says. At £2,860 for a king-size, the Artisan Bespoke 004 competes directly with mattresses from major luxury brands that offer considerably less upholstery specification at the same or higher price points.
| Specification | Origins Natural Comfort | Artisan Bespoke 004 |
|---|---|---|
| King-size price | £1,300 | £2,860 |
| Spring type | Spunbond pocket springs | Calico encased pocket springs |
| Spring count (king-size) | 1,000 | 1,600 |
| Spring format | Standard | 49mm / 1.4mm gauge |
| Total upholstery GSM | 2,550gsm | 3,600gsm |
| Key natural fibres | Wool, Cotton, Cashmere, Silk, Bamboo | Wool, Cotton, Horsetail, Bamboo |
| Construction | Two-sided, turnable | Two-sided, turnable |
| Mattress depth | 30 to 33cm | 27 to 30cm |
| Feel | Medium | Medium |
Frequently asked questions about Cortec springs
Are Cortec springs better than regular pocket springs?
Compared to standard glued-spun-bond pocket springs, Cortec springs have some genuine advantages: no adhesive in the construction, marginally more compression travel due to their elongated form, and a fully recyclable spring unit. Against calico-encased pocket springs, which are hand-stitched rather than glued and made from breathable natural Cotton, Cortec springs are less breathable, slightly slower to respond, and less structurally stable over the long term. For most buyers, the more important question is not which type of spring casing a mattress uses, but what natural fibre upholstery sits above those springs and whether the mattress is two-sided.
Why do some mattresses advertise spring counts of 10,000 or more?
Spring counts of this magnitude are achieved by combining two or more spring layers, typically a primary pocket spring unit paired with micro-spring layers made from very small, thin-gauge springs. Micro springs are genuine pocket springs, but they operate as comfort layers rather than structural support layers. Combining a primary spring count with micro-spring counts and presenting the total as the mattress spring count is a common marketing practice in the UK market. It is technically accurate but commercially misleading, because it implies a level of engineering sophistication that does not directly translate to better sleep. The space occupied by those additional spring layers almost always comes at the expense of natural fibre upholstery.
Are Cortec springs found in luxury mattresses?
Harrison Spinks uses Cortec springs across several price tiers, from their entry-level roll-pack mattresses through to their more premium hand-crafted collections. The Cortec spring unit itself does not indicate a luxury mattress. What determines whether a mattress is genuinely premium is the quality and depth of the natural fibre upholstery, the construction method, whether the mattress is two-sided, and the manufacturer’s overall transparency in specifications. A Cortec spring in a shallow, one-sided mattress with synthetic fillings is a marketing feature. A calico spring in a deep, two-sided mattress with thousands of grams of Wool, Horsetail, and Cashmere isan engineeredg feat.
Can I recycle a mattress with Cortec springs?
In theory, yes. The glue-free construction of Cortec springs makes the spring unit simpler to separate and recycle at the end of life. In practice, mattress recycling infrastructure in the UK remains very limited. Most local councils do not offer mattress collection for recycling. A handful of specialist recyclers operate nationally, and some retailers offer take-back schemes, though the actual recycling credentials of those schemes vary considerably. The most impactful sustainability choice you can make when buying a mattress is to choose one that will last as long as possible. A two-sided, natural fibre mattress that serves you well for fifteen years is substantially less damaging to the environment than a no-turn synthetic mattress replaced every seven years, regardless of whether its spring unit is technically recyclable.
What is the difference between spun-bond and calico pocket springs?
Spun-bond pocket springs are encased in a synthetic non-woven polymer fabric that is either glued or heat-sealed to form the individual pocket. They are the standard spring type used in the majority of mainstream mattresses. Calico pocket springs are encased in plain-woven Cotton fabric and hand-stitched together, with no adhesive or heat bonding at any stage. Calico springs are more breathable, faster to respond, and more structurally stable than synthetic-cased springs. They are also more expensive to produce and require skilled hand assembly, which is why they are found only in higher-end mattresses. The calico springs in our Artisan range are one of the primary reasons those mattresses perform and last as they do.
Is a higher spring count always better?
No. A spring count that is appropriate for the mattress depth and construction is better. Inflating spring counts beyond what the mattress volume sensibly accommodates requires either smaller springs, additional spring layers, or both. Each of those choices trades natural fibre upholstery depth for additional springs that contribute less structural benefit than the fibres they displace. A well-constructed mattress with 1,000 to 1,600 calico pocket springs and 3,000gsm or more of natural fibre upholstery will outperform a synthetic mattress with 10,000 springs and shallow polyester fillings in every meaningful measure of long-term comfort, durability, and sleep quality.
How do I know if a mattress has good upholstery specification?
Ask for the GSM weight of each upholstery layer and the total GSM across the mattress. A manufacturer confident in their specification will be able to tell you immediately. If a retailer can quote you a spring count to three significant figures but cannot tell you how much Wool or Cotton is in the mattress, that tells you something important about where the investment in that mattress has and has not been made. We publish the full GSM layer-by-layer specification for every mattress in our range as standard, because we believe you deserve to know exactly what you are buying.
Summary
The Cortec springs we sampled reacted very similarly to standard Spun Bond springs. Yes, they are slightly longer and thinner, so there are more of them. They also don’t contain glue, which is a nice benefit. It’s also nice to see Harrison’s innovation, trying to help increase recycling.
However, they still are housed in spunbond synthetic cases, which, compared to a Calico Cotton-encased Pocket Spring, will always be slightly slower to react. Calico is also far more breathable, making the bed cooler and easier to ventilate. We would also advise you to think carefully about choosing a one-sided mattress, meaning you can’t turn it. Based on our experience and hundreds of customer comments, these one-sided mattresses compress and rebound far faster.
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