What is a Bonnell Spring?

Hi Eddie.

Thanks for your question about what a Bonnell-sprung mattress is. Bonnell springs go by many names, such as open coil, cage sprung, Miracoil, Posture Tech and traditional spring, to name a few. This type of spring is the most basic possible in a mattress and is mass-produced and usually found in old or cheap mattresses.

What exactly is a Bonnell spring and where does it come from?

The Bonnell spring dates back to the 19th century and was originally developed for use in horse-drawn carriage seats. The coil itself is hourglass-shaped: wider at the top and bottom, narrower in the middle. Multiple springs are linked together using a helical wire, and a thicker border wire runs around the perimeter to give some edge structure. The Bonnell or open-coil spring unit is the cheapest and least effective support unit you can get in a mattress. It's a continuous piece of wire, which results in a one-size spring of sorts that moves as a mass piece. So when you move, the whole bed ripples and shakes with you. There is a lot of motion transference, as there is no isolation in the spring unit as it compresses. We have a more detailed article on why open coil mattresses should be avoided here.

Bonnell springs versus pocket springs: the key differences at a glance

If you want to understand this in more depth, our full guide to open coil versus pocket sprung mattresses covers each spring type in detail and explains why the step up to pocket springs makes such a significant difference in practice. You can find our article here.

What is memory foam?

This is a question we see regularly, and it is worth addressing directly. Memory mattresses can be a solid foam that has no springs at all or a hybrid of both memory foam and springs, whether pocket springs or Bonnell coil. It uses a dense polyurethane foam that responds to heat and pressure, slowly moulding around the body. This is often marketed as a comfort feature, but it comes with significant drawbacks: memory foam retains body heat, which causes a large proportion of sleepers to overheat; it responds slowly so turning over in the night feels effortful; and because the foam breaks down at a cellular level over time, many memory foam mattresses are functionally worn out within five to six years. You can find more information on memory foam here.

A Bonnell spring mattress sits at a similar price point but with a very different feel. It is bouncy rather than moulding, and it breathes better than solid foam because air can circulate through the open spring unit. However, as we have described above, it transfers motion freely and provides no tailored support.

What should you be looking for instead?

We only sell pocket spring mattresses and have never sold continuous coil mattresses. Pocket springs allow the most independent support, as each spring acts on its own rather than as one big rigid unit like the Bonnell. Pocket springs can also be tailored to your weight with specific spring gauges, whereas a Bonnell coil is nearly always the same gauge regardless of who is sleeping on it.

If you are starting to look at what to consider, our two most popular mattresses are a good place to begin. The Origins Pocket 1500 is our entry-level pocket spring mattress, made here in the UK with a 1,500 spun bond pocket spring unit and predominantly man-made upholstery. The Artisan Naturals steps up to a higher specification with calico pocket springs and 85% of natural fibres. Both have a two-sided build that substantially extends the mattress lifespan.

For a more detailed look at how to evaluate what is actually inside a mattress before you buy, our guide on how to choose a mattress is a good starting point. It walks through spring types, upholstery weights in GSM, and what questions to ask any retailer before committing.

Origins 1500 Pocket Spring Mattress

To help you with what to look for in a quality mattress, we would ask you to start by looking at the Origins 1500 mattress. When mattress shopping and working out how to choose a mattress, you need to start by asking exactly what is inside each mattress. The listing of this mattress will show you how to start uncovering what is inside a bed.

We do appreciate that if your budget is limited, you should still be looking for the best you can get. We do have our outlet section where we sell returned mattresses for up to 40% off.

If you need more advice when looking for a new mattress, then this video has all the insider tips that bed retailers try to keep hidden.

Why not call our friendly team on 0161 437 4419. You can find our office opening times here.

Kind Regards

Michaela