Understanding Spring Coil Systems
First and foremost, innersprings in general are among the longest lasting parts of a mattress and will outlast most polyurethane and memory foams as the support core of your mattress ages.
Although there is a wide variety of different innerspring mattress designs, the coils used inside them can be grouped into four main categories. These are Bonnell coils, Pocket coils, Offset coils and Continuous coils.
Amongst these different types of coils, there’s a wide difference in how well they shape themselves to an individual body profile and help the comfort layers of the mattress form a deeper cradle to relieve pressure around the body. Let’s dive in to these four types of coils!
Types of Coils
Pocket coils are individually-enclosed and function independently from one another. Unlike the other types of coils, pocket coils are not connected to each other with any type of wire. Because they work independently, they’re most effective at “body contouring,” or forming a cradle around the body. Each spring adjusts on its own to perfectly support your body in any sleeping position. Pocket coils are typically found in medium-to-high-priced mattresses as they are the most expensive type of coil to manufacture. Think the Beautyrest black line or an “online only” industry disrupter like WinkBeds. Pocket coils are kept together through the use of fabric “pockets” which are joined together (rather than the coils themselves being joined). These pockets have more independent movement, giving Pocket coils their greater “shape conforming” ability.
Bonnell coils are the original mattress coil. They have an hourglass shape and relatively simple design that engages when pressure is applied. Bonnell coils are considered a solid mid-range spring coil, but don’t provide nearly the same type of response range as Pocket or Offset coils. Because they’re less costly to manufacture and provide good value in comparison to their benefits, they are very popular in low-to-mid-range-priced mattresses. The coils are connected using a helical lacing technique, which involves a long spiral of wire that binds the rows together and borders the entire unit. These coil types act more together in a group with other coils because of the helical connections. The Saatva mattress is a good example of a mattress made with Bonnell coils.
Offset coils occupy a space between Pocket coils and Bonnell coils. They have a greater response range than Bonnell Coils but less individual body contouring effects than Pocket coils.
Continues coils are the least expensive coils to manufacture and have the lowest response range. They are generally used in lower quality and lower-priced bedding.
Gauge of Steel
The gauge of the steel used in spring coil systems refers to the thickness of the coil wire. This component plays a very significant role the overall feel of the mattress. The thickness of innerspring wire ranges from the thickest at 12.5-gauge to the thinnest at 18-gauge.
A high coil count in a mattress is generally a good thing, though it will eventually have diminishing returns. More coils mean more “active” points in the mattress. An active point means the mattress can flex and respond to your movements. The more active points, the better the mattress can contour to your individual shape and provide better response and support for your body. High coil counts are particularly important when it comes to mattresses made with Pocket coils. This is because pocket coils are comparatively smaller in diameter than the other types. Smaller coils means more active points in the mattress, which creates an independent response from each coil and provides more natural spinal alignment and more even pressure distribution. Since the coils flex individually, a collateral benefit is vastly reduced partner disturbance.
Coil counts and wire gauge work hand-in-hand to create overall mattress feel. Mattresses with high coil counts are best because the the coils distribute weight over a denser surface area.
Innersprings, like all support layers, are meant to control how deeply your heavier parts sink down into a mattress and help the comfort layers hold up your more recessed parts when necessary. Since pocket coils and offset coils have the greatest shape-conforming abilities, they usually make the best choices in more progressive spring coil-based mattress designs. The best quality mattresses tend to have high coil counts (over 2000 coils per queen). This ensures the sleepers weight is evenly distributed and the mattress will be durable over time.