Most people are accustomed to feeling that hallmark “bounce” of springs inside a mattress. They rarely stop to think about how those springs are designed (or why they were invented in the first place). However, if you briefly consider what that same mattress would feel like if the innerspring assembly was removed, suddenly a spring’s purpose becomes blatantly obvious. Without springs inside our beds, there’s no mechanism to provide our bodies with the responsive support they need to wake up feeling refreshed, and without joint pain.
A Brief History of the Innerspring Mattress
Though there’s some debate about the exact year innerspring mattresses were invented, and by who, most historians agree that it happened in the latter half of the 19th century. Around 1860, the first steel coil spring was patented for use (in chair seats). It wasn’t until around 1871 that a German named Heinrich Westphal used it while creating the first innerspring mattress. Unfortunately, Westphal never lived to profit from his invention. It was another 60-years before a quality innerspring mattress gained widespread adoption.
Wire Gauge Makes a Difference
When comparing springs of varying sizes in the palm of your hand, you’ve probably noticed that thicker wire is generally used for springs that need to support greater weight. For example, the springs on the shock absorbers of our cars are of a much heavier gauge than the tiny ones inside the retractable “clicker” on ballpoint pens.
Innerspring coils are typically created using steel wire. A thicker wire carries a lower numbered “gauge” than a thinner wire does. 14-gauge (1.63mm) wire is a good standard for higher quality mattress coils, while anything in the 15 ½ gauge (1.37mm) neighborhood is more likely to collapse under the pressure of an adult’s weight. At the other end, a 12.5-gauge (1.94mm) coil is about the thickest spring you’ll find in any mattress. Even though 12.5-gauge spring can support a lot of weight, most people find them too firm to be comfortable.
Different Coil Design Types
In the innerspring mattress category, essentially three different types of coil designs exist:
- Bonnell Coils: This is the oldest and still the most common coil design for most of today’s innerspring mattresses. Bonnell Coils are identifiable due to their hourglass shape. When laced together with cross wire helicals, they become a single assembly known as a Bonnell unit.
- Continuous Coils: The Continuous Coil design is unique from the Bonnell Coil. Continuous Coils use a single piece of wire throughout the entire mattress assembly. This does save manufacturers money by speeding up the assembly process. However it also results in a finished product that struggles to conform to your body’s natural curvature as you sleep.
- Offset Coils: These are the most recent (and advanced) innerspring coil design. While also identifiable by their hourglass shape, they also differ from Bonnel coils. Offset Coils take a portion of the top and bottom of each spring and flatten it, so it can then be hinged together with helical wires. This hinging effect helps the innerspring assembly unit conform to the natural curvatures of the body. It does so better than both Bonnell and Continuous coil designs. Advancing offset coil technology one step further, Sherwood Bedding’s quality innerspring mattresses utilize a unique double offset coil system. This design delivers firm, yet even more conforming support than traditional offset coils.
The real value indicator for any quality innerspring mattress is its support system. Most mass-marketed versions feature variants of the 80-year-old Bonnell coil design. While these spring units may have been state of the art during The Great Depression, they don’t exactly offer the consistent, edge-to-edge support expected by today’s discerning consumers.
Our Sherwood® line of mattresses feature an innovative open coil design that provides up to 21% more support than conventional innerspring mattresses. To experience just how significant a 21% boost in support feels, we invite you to find a Sherwood retailer in your area.