All About Cushion Foam Part 1: 4 Important Foam Terms to Know

Choosing the best foam for your application can make a world of difference in the cushion’s comfort and performance. Different types of foam have been engineered to float, drain water, and prevent mold and mildew. Which type of foam will make the best cockpit cushion, which is better for sleeping, and which is perfect for patios? To help answer those questions we’ve put together a three-part series on the ins and outs of outdoor foam. This is the first installment.

It’s always good to start with the basics. Today let’s look at some foam terminology you might run into when selecting foam. With a base understanding of these terms, you’ll be a step ahead in knowing what to look for when buying foam for any application.


4 Important Foam Terms to Know

Density: Expressed as weight in pounds per cubic foot, density is the most important property to consider when choosing foam. Density is a measurement of how little air is in the foam. Generally speaking, the higher the density, the better grade of foam. However, for certain projects a very high density can be considered excessive. For example, for boat cushions, the industry standard is only 1.2 lbs./cu.ft. for seat backs and 1.5-1.8 lbs./cu.ft. for seats. These densities are considered fine for occasional use such as on seasonal boats and patios. Indoor applications that see daily, year-round use would require a much higher density for longevity.

Indentation Force Deflection (IFD): This is a measurement of foam’s softness. This value is found through testing. A 50-square inch circular plate is pressed down onto the foam to a given deflection and then the force is read on a scale. The IFD represents how many pounds it takes to compress. A 30 IFD at 25%, therefore, means that it takes 30 lbs. per square inch to compress a 4-inch piece of foam 25% of its original height. Sailrite offers foam with firmness between 33 and 70 IFD. We refer to 33-35 IFD as medium soft, 40-45 IFD as medium, and 70 IFD as firm.

High Resilience (HR): High resilience foam gets its name from its properties that allow it to quickly regain its shape. HR foam has a more random cell structure when compared to other foams. This configuration of cells adds support, resilience and bounce. HR foam is generally supportive, comfortable and durable and is used in upholstery and mattresses. HR foam is better suited for indoor applications than out, as the moisture of an outdoor setting may compromise the properties of the foam.

Biocide: Biocide is an additive that reduces fungus growth in foam. A biocide treatment is recommended for outdoor foams that don’t easily drain water like polyurethane foams. All of Sailrite’s polyurethane foam comes pre-treated with biocide.

Be sure to check back tomorrow for our next installment in the Foam Series, 5 Types of Outdoor Cushion Foam. We’re going to break down different foam options and explore their features. You might even see some of these terms pop up!

  1. Ruth said:

    This is so helpful.

    • Nikki said:

      Good! Be sure to check back tomorrow for more foam facts!

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