Foam is everywhere. It is in engines, rugs, mattresses, boat seats and most things we interact with on a daily basis. If you sit or sleep on it, it probably has foam in it.
A brief history
Foam was originally made from latex taken from the sap of the rubber tree. Historically, there is evidence of foam being used by the Mayans and Aztecs dating back to 500 BC. While natural latex foams are still available, their use has been far outweighed by synthetic foam.
The first petroleum-based foam was developed in 1930 by Otto Bayer, an industrial chemist.
The onset of World War II and the resulting shortage of essential materials saw the development of urethane materials for fiber coatings and foam. By the late 1950s, polyether polyols appeared, laying the groundwork for tremendous growth in the polyurethane foam industry. Currently, the most common types of foam are ether- and ester-based polyurethane foams, although there is a rise in other oil-based “greener” foams, such as soy.
In a nutshell, synthetic foam is a mixture of polyol, isocyanate and water vigorously mixed together, poured onto a three-sided moving conveyor belt, and commonly produced in large buns called slabstock. After these buns cure, they are cut and shaped into smaller pieces in a variety of sizes, thicknesses and configurations.
Some foam products are injection molded. This is a process where the chemicals are poured into a mold of the final product, which is commonly how the foam for boat captain seats are created.
Foam buzz words
When discussing foam durability and feel, there are three main buzz words used in the industry that are often misunderstood: density, compression and resilience.
Density: This is the primary factor for durability, meaning how long a foam will maintain its original qualities before it breaks down. It is a measurement used to define how durable and supportive a foam is, but it does not determine the hardness or firmness of the foam. Foams with a higher density contain more foam and less air. The heavier the foam, the more support you will receive and the longer it will last. Measured in pounds (lbs.), density refers to how much foam is contained in a 12-by-12-by-12-inch block.
Something to keep in mind when creating a custom piece or replacing foam is how the weight of the foam will affect the performance of the final product. For example, a heavy foam mattress or a lot of cushions in a racing sailboat could affect the performance of the craft.
Compression: This is the main factor in determining firmness, but it is unrelated to durability. Firmness interprets the feel of the foam and how it yields to weight and pressure. This measurement, or test, is called “indentation load deflection” (ILD) and is determined using mechanical performance testing. The lower the ILD, the softer the foam. The higher the ILD, the firmer the foam.
Many people believe that the harder a foam feels, the longer it will last. This is a common misconception. Super hard foam with an ILD of 60 can come in 4.0 density or 1.0 density. The higher density foam always lasts longer.
Resilience: This determines how quickly foam will regain its shape, and it also determines its cost. To understand the cell structure of the two major types of foams, high resilience (HR) foam and conventional foam, envision a Jenga game of stacked blocks. The HR foam has the Jenga pieces crisscrossed and overlapped, providing both vertical and horizontal strength, which enables the foam to retain its shape longer. This complex cell structure is also what makes HR foam very expensive, as it is more costly to produce. HR foam is used in most types of expensive furniture, including mattresses for yachting and boating. We always encourage our clients to use HR foam in the salon and also in high-traffic seating areas. It is very buoyant and resilient.
With conventional foam, which is still a good foam and is used in 75 percent of soft good applications, the cell structure is like Jenga pieces that are stacked on top of each other like little towers close together. They provide vertical strength but are apt to collapse side to side. This cell structure is less costly to produce.
It is important to note that HR foam is a “high density” or HD foam, but not all HD foam is also HR foam. Therefore, two foams with the same density but different resilience can have significant price point differences.
Memory foam was developed by NASA scientists to reduce the stress on astronauts during takeoff and reentry into Earth’s atmosphere. The foam recipe was proprietary until the early 1980s when foam manufacturers gained access to the recipe, refined the formula and catapulted the foam into mainstream use.
One major complaint about early memory foams was that they retained heat easily, so foam companies added gel to the production recipe, which created a desired cooling effect. The temperature change made memory foam the desired top layer of a mattress or cushion set.
However, memory foam does have its drawbacks. One is that its soft, cradling qualities do not make it a good base layer. Because of this, I suggest you use a denser and more supportive layer of foam on the bottom and build the memory foam into the top comfort layer of your projects.
One of the biggest successes on the television show Shark Tank was the Scrub Daddy sponge, which is made from a reticulated foam. In terms of its cell structure, it works like a net scrunched together—water runs right through it. This makes it a great option for cockpit cushions and other outdoor cushion applications. That said, it is also perfectly fine to use standard or HR foam, if you’re careful to ensure proper drainage of the substrates.
Foam is a remarkable product, but understanding what type to use for different projects can be confusing. What is not confusing is that without all the different types of foam available today, our yachting and boating projects would not reach the level of quality or comfort that is now possible.
Rebecca Delano, with her husband, Troy, own Alfred’s Upholstery & Co. in Alfred, Maine. They have specialized in custom-built upholstered furniture, OEM work and marine soft goods since 1997. They received a 2021 MFA Fabrication Award of Excellence in the Marine Interior Upholstery category.
SIDEBAR: The layered cake effect
Multilayering foam provides unique comfort, particularly if you use a higher ILD foam as the foundation layer or to encase the edges of a project. This gives a nice defining edge to hold the cover’s shape and provides stability and security for the boater in rough seas.
- #1 Yellow; center of seat
- Density = 2.5–2.6
- ILD = 31–35
- #2 Blue; supporting bolsters on each side
- Foam density = 2.5–2.6
- ILD = 65–75
- #3 White; bolster inner layer
- Density = 0.9–1
- ILD = 24–34
- #4 Pink; center of seat
- Density=1.5 ILD=70
- #5 Pink; top of bolster
- Density=1.5 ILD=70