The Sponge Structure of Office Chair Seat Cushion & Back Cushion --- Foam

Today, let’s take a look at the sponge structure of office chair cushions and back cushions including its classification, hardness, density and elasticity of foam.

1. Classification of foam (manufacturing method)

a. Polymerized cotton: also known as recycled cotton, it is made by high-temperature fermentation and hot pressing of cut cotton waste.

b. Cut cotton: refers to the sponge that has been cut and pasted into a specific shape.

c. Molded cotton: It is a high-density sponge produced by opening the mold and has a soft feel to the touch and a smooth surface (PU foam molding).


2. The hardness of the foam

①Unit: degree

②The range of foam hardness is between 50-90.

3. The density of the foam

①Unit: kilogram cubic meter

②The range of foam density is between 18-50.

③Generally speaking, the foam density hardness of the seat of the chair > the foam density hardness of the back.

④The density of the chair will affect the seat resistance of the chair.

4.The impact of the density and hardness of the foam on the price

The hardness of the foam will not affect the price of the chair, only the density of the foam will affect the price.

5. Foam number

If the foam number is 1850, it means the density is 18 and the hardness is 50.

6. Fire test standards

  • California 117 in the United States
  • BS5852 in the United Kingdom
  • British BS7176 (including cloth and accessories)

7. The density of the foam determines the elasticity

We all know that there are many small holes in the foam. When the air is squeezed out, it will be deformed when subjected to external force.

In a relaxed state, the foam will slowly fill with air and return to its original state. This is the main principle of the working of sponge.

Therefore, the smaller the pores inside the foam, the better the elasticity of the foam for human body. This foam is a high-density sponge. The internationally recognized standard for high-density foam is: the weight of each cubic meter of foam reaches more than 45 kilograms.

And the high-quality, high-density molded foam is essential for all heavy-duty office chairs.

8. Wrong sitting posture will affect foam elasticity

Although chairs and sofas are bought for sitting, some wrong sitting postures can seriously damage the cushions and make the foam cushions lose their elasticity.

For example, in the habit of crossing the legs, the pressure on the human buttocks is on one side of the seat cushion. After long-term use, one side of the seat cushion will lose its elasticity.

If the foam cushion has lost its elasticity, consider the following methods to help the foam restore its elasticity.

Some ways to help the foam regain its elasticity

(1) Manual tapping can help the foam cushion to restore its elasticity. Of course, this method is only suitable for situations where the damage is not very serious.

(2) For cushions that can be removed and washed, you can add fabric softener in warm water, soak the cushions for 1-2 hours. And then take it out to dry. Help the foam cushion to restore its elasticity by soaking in water and kneading.

(3) The ultimate solution: add another cushion

If the above method does not work, the general business does not provide the service of replacing the cushion, so you can only choose to purchase another cushion.



2 thoughts on “The Sponge Structure of Office Chair Seat Cushion & Back Cushion — Foam”

  1. Hello.

    Can you tell me if seat cushion “The saddle-shaped cushion is crafted from high-density, one-piece molded cotton” is soft or firm on the firmness level ?

    Thank you.


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