Open Cell Foam

Open-cell foam is a foam whose cells are interconnected, allowing air and liquid to pass through easily. It is used in a wide range of applications, from cushioning and insulation to sound absorption and filtration.

This guide explains the characteristics of open-cell foam, how it compares to closed-cell foam, how it is made and where it is used.

Quick Reference: Open-Cell vs Closed-Cell Foam

Definition and Characteristics of Open-Cell Foam

In open-cell foam, the individual cells or bubbles are interconnected, allowing air and liquids to pass through. This open structure gives the foam its soft, flexible and breathable properties, making it ideal for applications that need cushioning, ventilation or moisture management.

Open-cell foams are typically low in density because of their high air content, making them lightweight and easy to compress. Another important characteristic is their ability to absorb sound, which makes them a popular choice for acoustic applications in buildings and vehicles.

Types of Open-Cell Foam

There are several types of open-cell foam, each with its own properties and uses:

• Polyurethane foam: The most common open-cell foam, used in furniture, bedding and packaging for its softness, flexibility and excellent cushioning.
• Latex foam: Used in mattresses and pillows for its durability and comfort.
• Melamine foam: Used for sound and thermal insulation, valued for its fire resistance.
• Reticulated foam: A very open, highly porous foam used in air filters and outdoor cushions because air and water pass through it easily.

Comparison to Closed-Cell Foam

The main difference between open-cell and closed-cell foam is cell structure. Open-cell foam has interconnected cells that allow air and liquids to pass through, while closed-cell foam has separate, sealed cells that trap air or gas inside, making it more rigid and less breathable.

Open-cell foam is softer, more flexible and more breathable, making it ideal for cushioning, ventilation and sound absorption. However, it is generally less effective as a thermal insulator and less resistant to moisture than closed-cell foam, which makes it less suitable for applications that need high strength, water resistance or thermal insulation.

Manufacturing Process of Open-Cell Foam

Manufacturing open-cell foam involves mixing, foaming, curing and cutting. For polyurethane foam, liquid raw materials react to form a polymer, while a blowing agent creates bubbles or cells within the mixture. The foam is then cured to harden it and set the cellular structure. Our foam manufacturing guide explains this in more detail.

Once cured, the foam is cut to the required shape and size using methods such as die cutting, water jet cutting or CNC machining. See our guide to foam cutting. The finished foam can then be further treated, for example with a fire retardant or water repellent.

Materials Used in Manufacturing

The materials depend on the type of foam. For polyurethane foam, the main materials are polyols and isocyanates, which react to form the polymer. A blowing agent creates the cells: this is often water, which reacts with the isocyanate to release carbon dioxide gas, although physical blowing agents can also be used.

Other materials include catalysts, which speed up the reaction, and surfactants, which help to stabilise the foam. Colourants, flame retardants and other additives may also be added depending on the properties required.

Environmental Impact and Sustainability

Like any industrial process, making open-cell foam has an environmental impact through raw material use, energy consumption and waste. Efforts to reduce this include using renewable or recycled materials, energy-efficient processes and waste reduction.

For example, some manufacturers now use plant-based polyols in polyurethane foam, reducing reliance on fossil fuels, while others recycle foam waste into new products (see our foam recycling guide). Designing foam products to last longer also reduces the need for replacement.

Applications of Open-Cell Foam

One of the most common uses of open-cell foam is in furniture and bedding, where it is used in cushions, mattresses and pillows. Its softness, flexibility and breathability provide comfort and support while allowing air to circulate. See our guide to foam cushioning.

Open-cell foam is also used in foam insulation to reduce heat transfer and sound transmission in buildings and vehicles. It is particularly effective at absorbing sound, although it is less effective than closed-cell foam as a thermal insulator.

Use in Packaging

In foam packaging, open-cell foam protects delicate items such as electronics and glassware during transport by absorbing shocks and vibrations. It is lightweight and easy to cut and shape for a snug, secure fit.

It can also fill voids in boxes to stop contents moving around, and be used for custom foam inserts or foam-lined boxes that provide both protection and presentation for valuable items.

Use in Filtration

Open-cell foam’s open structure and high porosity make it an effective filter medium in air filters, water filters and other filtration systems, trapping particles while allowing air or liquid to pass through.

Filtration performance depends on pore size and density, which can be controlled during manufacture. Smaller pores and higher density increase filtration efficiency but also restrict flow, so filters are designed to balance the two. Foam filters may need regular cleaning or replacement to prevent clogging.

Advantages and Disadvantages of Open-Cell Foam

Like any material, open-cell foam has advantages and disadvantages to consider when choosing it for a specific application.

Advantages in Detail

• Comfort: Its softness and flexibility allow it to conform to the body, making it ideal for cushioning and padding.
• Breathability: Air and moisture vapour can pass through, helping to regulate temperature in bedding and upholstery.
• Sound absorption: Its open structure absorbs sound, making it popular for acoustic applications.
• Light weight and ease of use: It is easy to handle, transport, cut and shape.
• Cost: It is relatively inexpensive to produce, offering a good balance of performance and cost.

Disadvantages in Detail

• Durability: Lower-density open-cell foams are more prone to wear and can lose their shape or firmness over time, making them less suited to heavy-duty uses. See our guide to foam density.
• Thermal insulation and moisture: Open-cell foam is less effective than closed-cell foam as a thermal insulator and allows water to pass through, making it less suitable for building insulation where high thermal resistance is required.

Final Thoughts

Open-cell foam is a versatile material valued for its softness, flexibility, breathability, sound absorption and filtration capabilities, making it important in furniture, bedding, packaging, insulation and filtration. Its main limitations (lower thermal insulation and moisture resistance than closed-cell foam) mean it is worth understanding both types before choosing a foam for your project.

Explore Related Foam Guides

Continue exploring foam types and properties across our technical glossary:

• Closed-Cell Foam: Why sealed cells resist water and insulate well.
• Polyurethane Foam: The most widely used open-cell foam.
• Latex Foam: Natural and synthetic latex for mattresses and cushions.
• Foam Properties Overview: How cell structure and chemistry shape foam performance.
• Foam Insulation: How open- and closed-cell foams reduce heat and sound transfer.
• Outdoor Cushions: Choosing foam and fabrics for outdoor seating.

Looking for Open-Cell Foam Cut to Size?

Whether you need soft, breathable foam for sofa cushions, mattresses or outdoor seating, the Foam & Covers team can help you choose the right open-cell foam and cut it precisely to your measurements.

Contact Our Foam Specialists or Order Custom Cut Foam Online .