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3 Easy Steps to Understand Foam Density in Upholstery

15 Mar. 2021
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Foam density is one of the most important aspects of a sofa. However, it is hardly discussed. In fact, most people don’t understand foam density in upholstery. Whether you prefer soft or firm cushions, you should think about foam density before you buy a couch. At this point, you may be wondering what’s so special about foam density. Let us show you! Here are 3 easy steps to understand foam density in upholstery.

Cozey Couch in Dark Grey. 3 Easy Steps to Understand Foam Density in Upholstery
Cozey Couch in Dark Grey

Step 1: Understand the Difference Between Firmness and Density.

Firmness and density may sound related. After all, density directly impacts firmness in most cases. However, in the case of upholstery, firmness and density do not always correlate. Here are some definitions:

Foam density is the amount of material in each square foot of foam. We measure foam density by weighing a 12″ x 12″ x 12″ piece of foam. Foam density typically falls within the range of 0.8Lbs and 3.0Lbs. Foams have different uses based on their density. See step 3 for more on this.

In simple terms, Foam firmness defines how hard or soft foam feels. Foam firmness is also called Indentation Load Deflection (ILD). We determine ILD by measuring how much force it takes for a 50 square inch plate to compress a 15″ x 15″ x 4″ piece of foam down to 75% of its thickness. If it takes 10Lbs of force to compress the foam, we give the foam an ILD value of 10. Similarly, if it takes 70Lbs of force to compress the foam, we give that foam an ILD value of 70. The typical range of ILDs is 8 to 70. Some foams can be as high as 150.

Yup. Thorough furniture shopping looks a lot like math class.

What Makes a Good Couch via Pinterest.
What Makes a Good Couch via Pinterest

What To Look For…

You may be wondering what type of firmness to look for in a sofa. The answer to that is completely up to you. If you’re wondering what type of foam density to get, the answer is a little more complicated. Consider these 2 things when deciding on a foam density for your couch:

  1. Budget. Higher quality foams typically have a higher density than lower quality foams. Thus, higher density foams are usually more expensive than lower density foams. However, higher density foams last significantly longer than lower density foams. How much longer they last depends on thickness and–
  2. Use. If you plan on using your couch every day, high density cushions may be right for you. However, if you plan on using the couch occasionally, you don’t need something extremely dense. A heavily used, dense cushion will last about as long as a rarely used, light cushion.
Old, Worn Out Couch via Houzz
Old, Worn Out Couch via Houzz

See this article for more details on foam density.

Step 2: Understand The Characteristics of Open-Cell Foam

Typically, upholstery uses open-cell foam. Open-cell foam is pictured on the right.

Closed-cell foam (left) versus open-cell foam (right). Picture from ResearchGate.
Closed-cell foam (left) versus open-cell foam (right). Picture from ResearchGate.

Foam is made of tiny bubbles– also known as cells. In closed-cell foam, these cells are small and connected. In open-cell foam, the cells take on a barely connected, web-like structure. This means water and air can pass through more easily. However, some open-cell foams release water better. On the other hand, closed-cell foams are almost always water resistant. Overall, the two are very different. In this article, we will only cover open-cell foam.

In the paragraph above, we mentioned that cells make up foam. These cells are different sizes and thicknesses. By size, we mean the area of a cell. By thickness, we mean the amount of material around each cell. Both the size and thickness of cells impact density. When cells are smaller, the amount of material per cell increases. When the cell wall is thicker, it is stronger. In other words, it takes more pressure to compress. A foam with thicker cell walls takes longer to break down than one with thinner cell walls.

Most of the time, open-cell foams have more air in them than closed-cell foams. This is even true of open-cell foams with thick cell walls. The high level of air in open-cell foam makes it more elastic than closed-cell foam. It is also softer. Open-cell foam’s soft, malleable nature makes it perfect for upholstery.

Step 3: Understand the Density Scale

Back at step one, we mentioned that foam density fits on a scale. Here is that scale, explained. The following information is from this article. Visit the Foam By Mail website for more.

Level 1: 0.8Lb-1.5Lb Density

This level contains foams of ‘fair quality.’ Foams in this category have low densities. This means there is less material and more air. Because there is less material, the foam breaks down faster. Low density foams are used for shipping. They are cheap and they get the job done. They can also be used as bed toppers in guest rooms. As long as they don’t get used often, low density foams are very useful!

Fair Quality, or Low Density Foam via Foam By Mail
Fair Quality, or Low Density Foam via Foam By Mail

Level 2: 1.6Lb-2.4Lb Density

This level contains foams of ‘good quality’. Foams in this category differ a lot in terms of density. At the low end are the most commonly used foam densities. Foams with a 1.8Lb density are the single most commonly used foams in furniture. A 1.8Lb density foam will typically begin to lose its shape in 1-3 years. Of course, this depends on its level of use.

Good Quality, or Medium Density Foam via Foam By Mail
Good Quality, or Medium Density Foam via Foam By Mail

Level 3: 2.5Lb-3.5Lb Density

Foams in this density category are the best of the best. They are used for high quality mattresses and sofas. The difference between mid-density and high-density foams is longevity. Many people ‘invest’ in high-density foams to avoid spending money on more foam in the long run.

High Quality, or High Density Foam via Foam By Mail
High Quality, or High Density Foam via Foam By Mail

All in all, it is important to understand foam density in upholstery. Knowledge saves money!

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