Almost eleven months ago I posted an article about wood coils, a new kind of mattress innerspring invented and developed by a Hungarian company. Not long before the launch of wooden coils in the bedding market, another new kind of mattress spring was invented and introduced into the market by Willy Poppe, a Belgian. Poppe is CEO of a family-owned bedding manufacturer, Diamond Spring Company, in Sint-Niklaas, East Flanders, Belgium.
Willy Poppe’s invention is the foam spring, an eight-sided hollow column made of memory foam. The column is cut in a honeycomb pattern, which resembles expanded metal. Poppe dubbed this “Octaspring.” the Octaspring can be compressed like a spring. According to Willy Poppe in a video, these MemoryCoils were first used in memory foam pillows. However, while these memory foam springs worked well in pillows, they were not firm enough for mattresses. So the Octasprings were reinforced with the addition of firmer polyurethane. These EcoSprings could be made soft or firm or somewhere in between.
Now a grid of Octasprings would be the support core of a mattress. With a 1″ foam layer between, one layer of foam springs can be placed on another. Dormeo, a company set up to manufacture and distribute Octaspring memory foam matresses, has models with one to three foam core layers.
One advantage of foam springs instead of metal is that they are not felt the way metal springs are. Also, like the wood coils reviewed earlier, they do not focus environmental electromagnetic radiation on the users.
An additional advantage is airflow. The honeycomb cuts go all the way to the open core of the Octaspring, allowing air to flow all the way through. Pressing down on the “coil” forces air out, and releasing pressure lets it back in. So any movement by the sleeper pumps air through the mattress, increasing the cooling effect, another advantage over metal springs.
The article on wooden coils ended with a paragraph asking, “What Will They Make Springs from Next?” Foam springs were already being made, and foam spring mattresses are selling. Look for other firms to develop their own types of foam springs or buy a license to make Octasprings, the way that Tempur-Pedic was quickly and widely imitated in using memory foam.
Nylon is a thermoplastic amide polymer.* Invented in 1935 by DuPont chemical engineer Wallace Carothers and first used for toothbrush bristles, nylon is the most used synthetic fiber. In 1940 it was introduced as a substitute for silk in stockings. Nylon is very similar to silk, and with Japanese occupation of China the supply of silk was restricted. Then in 1942, nylon replaced silk in parachutes. Ripstop nylon, developed for sturdier parachutes, is now used for tents and awnings, coats, ponchos, and bags. And solid nylon is used for gears, rollers and bearings in light applications. By the way, it is still widely used for toothbrush bristles.
Nylon is also used in mattresses. Invacare and Paramount Mattress use nylon in covers of institutional and healthcare mattresses. Some Beautyrest Recharge mattresses use a nylon/polyester blend. Boyd Specialty Sleep uses nylon tricot in the covers of the support modules for its Broyhill Cube Series mattresses.
The two variations of nylon used today are nylon 6,6 and nylon 6. With essentially the same final product, the difference between these two is how they are made. The 6 stands for the six carbon atoms in the precursor molecule. Nylon 6,6 was patented by DuPont, so other manufacturers had to find another way to make nylon. DuPont‘s process simply linked two six-carbon chain molecules together with amide bonds (which also exist in silk). Other manufacturers discovered how to open the ring of an aromatic molecule (one with a six-carbon ring) and link it to others. Either way, what you get is nylon.
Two other types of fiber developed from nylon are Kevlar® and Nomex®. Nomex replaced asbestos in fireproof clothing, and Kevlar is used for bulletproof vests. These are called aramids, because they are actually made of carbon rings.
Nylon is not widely used in mattress covers. Except for the Beautyrest Recharge, it is used in top panels of healthcare and institutional beds. The advantage of nylon in this usage is that it can be resist fluids and still be breathable. This protects the mattress foam core and is easy to clean without trapping heat the way totally impermeable vinyl would. Boyd uses it for its support cubes so they can be removed and reinserted easily.
Thermoplastic means that it gets softer when heated.
Polymer means that it is made of bonded chains of similar molecules.
Amide means that one molecule is bonded to the next by an amide group: one atom of nitrogen with a hydrogen atom (NH) linked to a carbon atom with a double bond to an oxygen atom (C=O). The link can be typed out as NH-C=O. The two components are linked to the N and the C respectively.
Several manufacturers claim that some or all of the foams used in their mattresses are either partially or wholly made from plant oils. Terms used for these are soy foam, plant-based, botanical-oil, natural oils, etc. Plant oils used include those extracted from soy beans, castor beans, canola (rapeseed), palm kernel, coconut, peanuts, and other seeds. How are these oils used in making foam? And how does this affect the use of fossil fuel sources (petroleum and coal oil)?
Oil itself does not form foam, at least not the kind you can sleep on. Bedding and furniture foams, other than latex foam (foam rubber), are forms of polyurethane foam, a semi-rigid, flexible material which is both supportive and cushioning. Polyurethane is a polymer, chains of repeated links of molecules. These molecules are polyols, alcohols with several hydroxyl branches. An alcohol is an oil (hydrocarbon) which is partly oxidized. A hydroxyl is an -OH branch of oxygen and hydrogen.
Some polyols are always produced when refining petroleum. One plant oil, castor bean oil, contains a natural polyol. Most other plant oils have to be modifed to make polyols. The components of these oils are fatty acids, like mono-, di- and triglycerides, the precursors of cholesterol. The fatty acids used are long chains with a double carbon bond (C=C on a diagram) in the middle. Using ozone or other reactors, hydroxyls are added to the chains.
To make the polyurethane, the polyols are combined with isocyanates. The reactions form endless chains which cross-link to form the polyurethane. Gasses released by the reactions and air introduced during the process make the foam.
Until recently, only a small portion of petroleum in polyurethane foam could be replace by plant polyols (aka biopolyols) and still produce a quality foam. Refinement of the process, including using water for the solvent, make it possible to use a higher percentage of biopolyols. However, we need to carefully examine the claims of manufacturers and retailers in promoting their products. Don’t be afraid to ask what proportion of the oils used in making the foams are plant derived.
Use of polyols derived from natural plant oils reduces the use of petroleum in more than one way. First, it means less petroleum is used as the raw material. Second, this means less petroleum used as fuel for refining petroleum for polyols. Third, modifying plant oils requires less energy.
Other advantages of using plant polyols in manufacturing polyurethane and its derivative foams include 1) less or no VOCs (volatile organic compounds), and 2) less degradation of the foam by moisture (such as from sweat), and some plant-oil foams are less flammable.
However, use of plant oils has its own environmental concerns. First is land use for growing plant oil crops. Is the land chosen wisely? Or does it degrade natural resources (such as rain forests)? Second, are the farming practices environmentally acceptable? This includes preventing erosion and whether chemical pesticides, herbicides and fertilizers are used. Also, does raising and using plants for this purpose compete with food crops, thereby raising food prices?
In the final analysis, using natural plant oils to make polyurethane, memory foam, and other foams for bedding products is a net benefit for health, safety, and the environment. And this will grow as technological development improves the processes involved.
Damask is not a fiber, but a style of weaving, named for Damascus, Syria, where silk and linen were woven in this manner in the early Middle Ages. In damask weaving, patterns are created by longer warp threads on top (satin) for the foreground, and longer woof threads (sateen) for the background. This pattern is reversible, meaning the the negative image appears on the back side of the fabric. This was more commonly done with one color (monochrome). Damask can also be done with multiple colors (polychrome). In either case, the image is created by the pattern of weaving.
At the end of the Middle Ages, the art of damask weaving was brought to Italy, then spread across Europe. Many damask fabrics used in the bedding industries are produced in Belgium.
Today, most damask weaving is done with Jacquard looms. Invented in 1801 in France, these were controlled by punched paper cards, then by punch-hole paper tape. Now jacquard looms are controlled by digital computers.
The most common uses of damask are in tablecloths and draperies, sometimes in clothing. Several bedding manufacturers, for example Simmons Beautyrest, Sealy, E. S. Kluft, and Parklane Mattresses, use damask in the covers of some of their mattresses, often with the name and/or logo of the company repeated in the pattern.
Besides weaving, a style of knitting producing the same effect, also called damask, is used on mattresses, especially memory foam, latex, or foam-topped models. Fibers used include cotton, linen, polyester, silk and rayon.
Cashmere is also known as cashmere wool, though it is not really wool (like that shorn from sheep), but a type of goat hair. It is considered a luxury fabric, more expensive than wool. Whether woven or knit, it is a fine fabric which becomes softer with use. Commonly used in shawls, sweaters, scarves and hats, cashmere is also used by some manufacturers in the covers of select mattresses. A few of these manufacturers are Kingsdown, Magniflex, Stearns & Foster, Simmons Beautyrest, Parklane, Spring Air, Serta, Shifman, and E. S. Kluft.
Cashmere is considered a warmer fabric, while silk is considered cool. Therefore it is sometimes paired with silk in flippable toppers with a Winter side and a Summer side.
Cashmere, is named after Kashmir (Cashmere is the British spelling), a former kingdom in an area now divided between India and Pakistan. This is where commercial production of cashmere began in the Middle Ages. Before this, cashmere fabric was made and used locally.
Cashmere is the undercoat of long-haired goats [Capra hircus laniger and related breeds], which are now known as cashmere goats. These goats originated in Kashmir and adjoining areas, then spread through China into Mongolia as herders migrated. Currently, the three largest producers of cashmere hair (also called cashmere wool) are China, Mongolia and Afghanistan.
To be legitimately called cashmere, the fibers must meet certain standards. United States law (U.S. Wool Products Labeling Act of 1939) defines cashmere as 1) the finer, softer undercoat (also called down) of the cashmere goat, 2) with an average fiber diameter 19 microns or less, and 3) less than 3% of fibers larger than 30 microns in diameter.
The common method of gathering the down is combing it out when the goat is shedding. After this, the hair is washed, then the longer coarse guard hairs are removed. It is the combed raw cashmere which is usually sold on the world market. Buyers of raw cashmere spin it into thread and yarn.
Production of cashmere textiles in Europe began when Marco Polo brought cashmere back to Italy in the 1200s. In the 1800s cashmere textile production began in France and Scotland. It spread to America in the 20th Century.
Care instructions for cashmere most commonly say, “Dry Clean Only.” But the best method for cleaning cashmere is hand-washing in cold water, blotting and laying flat to dry without heat.
Pocket coils were invented at the end of the 19th Century (1800’s) by James Marshall, who began manufacturing them about 1900. Since then, individually wrapped pocket coils have been adopted by most of the major manufacturers of innerspring mattresses.
A more recent development in pocket coils is coil-in-coil technology. The concept is simple: a smaller, firmer coil inside a larger, softer coil. Two of the mattress companies using this technology state that the two coils are made from one wire, and photos of the others show this feature, which is also described in the patent application. Most of the coil-in-coil springs are straight cylinders, but the Joey Coils used by Simmons Singapore are barrel-shaped (a little narrower at the ends).
Before this, manufacturers had used other means to make dual-response springs. The oldest method was the hourglass shape, as in Bonnell coils. The narrower middle with more stretched-out turns compresses more easily for a softer response, while the broader ends with more closely spaced turns is firmer for more support. This concept is also exhibited in offset coils. At least one manufacturer tried variable-gauge coils and S-springs, where part of the spring wire is a heavier gauge. Also tried is alternating heavier and lighter coils.
Sometimes called “dual coil technology” (not to be confused with one coil layer atop another), there are a number of trade names for springs using this technology. For instance, Leggett & Platt Components Europe makes Joey Coils. According to A.H. Beard, the Australian mattress company, they are named after the kangaroo and are sometimes called “pouched coils.” The Serta iSeries hybrid mattresses use Duet™ Coils. And in Stearns & Foster‘s Estate Collection these are Intellicoil® Encased Coils.
Coil-in-coil technology is not as widely used as the parent pocket coils are, mostly due to how new they are—less than a decade. But usage is significant considering who uses it: Stearns & Foster, Serta, Paramount Sleep, and Simmons. These are the companies whose lead is followed by others. Coil-in-coil technology may also be used in children’s mattresses (called 2-in-1 coils with a graded response), but I do not yet have confirmation of this.
Coil-in-coil technology is, for now, used in more expensive mattresses. However, their use in Serta‘s middle-priced iSeries models points to a future of more efficient production with lower costs, resulting in a more widespread presence in mattresses. A key advantage for them is the suitability of the coil-in-coil design for couples of significantly different body sizes.
Pocket coils, also known as pocketed coils, encased coils, wrapped coils or Marshall coils, are light gauge open-end coils in fabric pockets. They were invented in 1900 by James Marshall, an Englishman who migrated to Canada. In Toronto, Ontario, Canada he founded the Marshall Mattress Company to make mattresses using his technology. The company is still in business, focusing solely on pocket coil mattresses. It was featured in a 2011 BedTimes Magazine story.
The pockets are attached to each other, but the coils are not. This allows each coil to respond independently to weight place directly on it. According to Brad Warner, owner of Marshall Mattress, the pocket coils were invented to meet a need: “Legend has it that Mrs. M. was bedridden and Marshall created the support system for her, with coils wrapped in unbleached muslin, quilted with horsehair and outer tufted.”
At first, since they had to be made and encased by hand, pocket coils cost so much to manufacture that they could be used in only the most expensive mattresses. Then in 1925, Simmons engineer J. F. Gail invented a machine to make the coils and insert them into cotton pockets. This reduced the cost of a pocket coil mattress enough to place it in the general market.
Pocket coils are now very common around the globe. According to Marshall Mattress, “Marshall’s pocket spring-filled mattress system has become the original worldwide standard for spring-filled mattress construction and remains to this day.”
The main advantage of Marshall coils is the individualized support they offer. The independent response of each coil conforms the entire unit to the shape of the user’s body, resulting in even support for the entire body. This means two things:
(1) Larger parts of the body do not bear a disproportionate load. This reduces or eliminates pressure points.
(2) In-between sections of the body are supported. This keeps the spine in proper posture, relieving or preventing back and neck pain.
Refinement of pocket coils is ongoing. Relatively recent developments are microcoils and dual coils. Microcoils are short, small diameter pocket coils. Though no industry-wide standard definition of microcoil has been set, the term is used for coils as much as 4″ tall.
Dual coils are a coil-in-coil design, first patented in 2010 by Sealy engineer L. K. DeMoss. The two coils are made of one wire. They turn in opposite directions. The outer coil is taller with fewer turns, making it more responsive. The inner coil is short and has more turns, making it more supportive. This configuration makes it more durable than the hourglass figure of Bonnell coils, which also have a dual response.
Another development in pocket coils is tall coils, some as much as 10″ high. The objective of this development is to make the mattress less dependent on less durable comfort materials such as memory foam, latex, and foam in general, as well as reducing the overall height of ultra plush innerspring mattresses.
Though pocket coil technology is over 115 years old, the basic value of individually wrapped pocket coils along with continuing development of this form of innerspring support indicates that Marshall coils are here to stay.
Continuous coils are the least expensive type of coils used in innerspring mattresses. According to Seattle Mattress Company, this coil type was invented by Serta. Currently, Serta is the largest user of continuous coils. Serta‘s continuous coils are manufactured by Leggett & Platt under the trade name Miracoil. Continuous coils are among the five most commonly used innerspring coil systems. The other coil types are Bonnell coils, knotted and un-knotted offset coils, and pocket (Marshall) coils (which also includes micro-coils).
Continuous coils are so-named because an entire row of coils is formed from one continuous wire (see picture above). Each row is tied to the next row by a spiral (helical) wire. The wire forms one coil going up and the next going down, which means the coils are paired, The helical wire also links one end of a coil pair to the end of the next pair in the row (see picture below).
The benefits of continuous coils include affordability, durability, stability, and consistent support. They also enable greater coil density, which makes support smoother. As with other coil systems, the goal is to enable the users to experience quality sleep.
The principal drawback of continuous coils is that motion is transferred along the row. For this reason, coil rows usually run head-to-toe. The helical connection of one row to another acts like a hinge, providing more flexibility across the mattress to lessen motion transfer between sleeping partners. This also reduces the load carried by each individual coil.
Some mattress models have rows of continuous coils both lengthwise and crosswise. This significantly increases coil density, enabling the mattress to support more weight.
Offset coils, also called Karr coils, were invented in the early 1900s by Frank Karr, who also started the Spring Air mattress company. They were developed from Bonnell coils, the original support for innerspring mattresses. Since the inception of offset coils, they have been used by many other mattress companies.
The principal distinction of offset coils from Bonnells is the shape of the ends. The top and bottom ends of Bonnell coils are round. Then they are tied into rows by spiral wires. The ends of offset coils are squared at opposite ends. The squared ends of one coil are tied to those of the next coil with a helical wire. This functions as a hinge, which allows each coil to respond individually, making an offset coil innerspring unit more flexible than a Bonnell.
The flexibility of offset coils reduces pressure points on protruding parts of the body, such as shoulders and hips. This also means better back support, especially for side sleepers. Additionally, this reduces motion transfer. Alternating right-hand turning coils with left-handed ones makes the mattress more stable by countering any tendency to lean one direction or the other.
There are two basic forms of offset coils, knotted and un-knotted. Knotted ones are more stable and have a smoother feel. Un-knotted Karr coils are springier and more flexible.
Because they are more complex, offset coils cost more to make and assemble. thus they are usually found in the more expensive higher-end models of mattresses. Those who can afford them value offset coils over Bonnell coils for both their durability and the quality of sleep provided by greater comfort.
The oldest type of coil used in mattresses is the Bonnell coil. Bonnell coil mattresses are often called “traditional mattresses” or “traditional innerspring mattresses.” Other types of coils have been developed since, but they all originate in the Bonnell coil.
Bonnell coils themselves were developed from buggy seat springs. They are hourglass shaped. The ends are knotted, the end of the wire twisted around the coil wire, making a full circle (see the single coil in the illustration above). The coils are attached to each other in rows by a helical wire (see middle picture). And all the rows together in a heavy wire (or perimeter rod) frame form the innerspring unit.
The hourglass shape of a Bonnell coil gives it a dual action. The narrower middle is “softer” with an initial yield when a weight is placed on it. Then the wider ends increase resistance for “deep down” support.
The narrow middle section is a weak point in this type of coil, making it prone to distortion or breakage leading to mattress sagging. Nevertheless, Bonnell mattresses give good support when new. Thicker-gauge wire and/or a less-pronounced hourglass figure make a Bonnell coil more durable. At the same time, this makes the innerspring firmer. This is the reason Bonnell coils are usually found in firmer mattress models. A taller coil or fewer turns can make heavier-gauge coils less firm without sacrificing durability.
Bonnell coils cost less to manufacture and assemble than other types. Therefore they are usually found in lower-priced entry level innerspring mattresses. If a sleeper or a couple are not too heavy, a well-designed and made Bonnell coil mattress can last a reasonably long time.
Best Latex Mattress
Best Memory Foam Mattress
Best Pillow-Top Mattress
Mattress Ratings Criteria
Best Hotel Beds
Choosing the Correct Bed Firmness
When is it time for a new Bed
Back Pain and Your Mattress