SPEAKING OF SPRINGS

Innersprings withstand the test of time.

With all of the buzz about "specialty sleep", are you forgetting about the basics? Remember, innerspring-based constructions are still the backbone of the business and continue to account for the majority of mattress unit sales. So we thought it fitting to begin with a refresher on the cornerstone of the American mattress market.

What is it about coiled steel wire that makes it so suitable for sleeping on? It's actually a rather ingenious application of the physics first described in 1676 by Hooke's Law, which said: "The power of any springy body is in the same proportion with the extension," thereby announcing the birth of elasticity.

Even the earliest springs demonstrated unique characteristics – a combination of flexibility and consistent support – and when properly made, they proved remarkably durable. That's still true 300 years later. The first coil spring construction for bedding was patented in 1865, debuting as open bedsprings under cotton-filled mattresses. Germany's Heinrich Westphal is credited for inventing the innerspring mattress in 1871. He died in poverty, having never profited from his invention. It wasn't until the 1920's that innerspring mattresses and upholstered box springs began to be viewed as the best in modern sleep support.

Many ways to turn
The essential physics behind a coil spring's strong performance in bedding (and furniture) haven't changed, but mattress manufacturers and their suppliers have discovered many ways to refine and fine-tune spring constructions to create different levels of support and comfort. The number of wire "turns" in the coil, the gauge of the wire, the way the wire and unit are "tempered", the number of coils in a unit, the shape of the coil, the way the coils are connected and, of course, the cushioning materials that are married to the spring units – all can be varied to create new designs with an endless array of comfort characteristics. Technological enhancements continue in the 21st century – as your vendors are more than happy to demonstrate.

Coil-count caveats
Selling mattresses by coil count – "This model is better because it has twice as many coils!" – has fallen out of favor, with good reason. Though coil count can affect weight distribution and mattress feel, it shouldn't be used as the ultimate determining factor for comfort, firmness, durability or overall quality. It is just one among many factors that affect total performance. But a baseline coil count can come in handy, says the American Innersprings Manufacturers (AIM), which offers the following guidelines:

• A full-size mattress should have at least 300 coils.
• A queen-size mattress should have at least 375 coils.
• A king-size mattress should have at least 459 coils.

These numbers represent the crossover point between bargain-basement bedding and bedding that provides good basic support.

What research shows
There is no definitive research comparing different types of mattress support – a virtual impossibility because of the many variables and possible combinations in mattress construction. But according to AIM, research conducted at the University of Memphis and sponsored by AIM has shown that innerspring mattresses offer superior performance when it comes to support, minimizing lower back strains while lying on both the supine and side positions.