Types of Foam Explained – A Glossary
As the UK’s largest foam supplier, dedicated to delivering top-quality foam solutions for a multitude of applications, we want to make sure that you’re completely in the know when it comes to purchasing foam.
To help define various foam-related terms you might encounter, this guide is organised into four sections: foam basics and materials, types of foam by application, acoustic treatment terms, and units of measurement and testing.
Our experts know all there is to know about foam and we’re always happy to answer any questions you may have. If you’re unsure about something or just want to find out more about our products, please feel free to get in touch.
Foam Basics: Structure and Materials
Every foam starts with its cellular structure and base material, and these fundamentals shape how it feels, performs and where it’s best used. Here are the core terms you’ll come across.
| Term | Definition |
|---|---|
| Antistatic Foam | A foam engineered to exhibit antistatic properties to help reduce or eliminate the build-up of static electricity. This is often used to store or package sensitive electronic equipment. |
| Closed-Cell Foam | A type of foam where the cell walls are intact, causing the foam to be more rigid and resistant to fluids, chemicals and more. |
| Ethylene-Vinyl Acetate (EVA) | A type of closed-cell foam known for its durability and flexibility, commonly used in sports equipment, footwear, costume making, prop making and more. |
| High Density Foam (HD) | A type of foam that has a high weight per cubic foot, often used in upholstery for its durability and support. A high density does not necessarily correlate with the firmness of the foam. |
| Open-Cell Foam | A type of foam where the cell walls, or surfaces of the bubbles, are broken and air fills the spaces in the material. This makes the foam softer and more flexible. |
| Plastazote | An advanced type of closed-cell polyethylene (PE) foam blown with nitrogen. Manufactured by Zotefoams PLC and part of the Azote range, which also includes Evazote and Supazote. This is the closed-cell foam we stock and cut to size. |
| Polyurethane Foam (PU) | A versatile and popular type of foam that is used in a wide variety of applications, including mattresses, furniture and various types of insulation. |
Types of Foam by Application
Beyond the basic structure, foam is often grouped by what it’s actually used for. Here are the main types you’ll find across furniture, fire safety, outdoor use and more.
| Term | Definition |
|---|---|
| Acoustic Foam | A special type of foam used to control echoes and background noise in a room. Its open-cell structure is designed to absorb sound waves and minimise sound wave reflections that cause interference. |
| Class 0 Foam | A type of acoustic foam with superior fire resistance. Manufactured to meet Class 0 requirements and often used in the construction industry. |
| CMHR Foam | Combustion Modified High Resilience foam, used mainly in furniture to meet UK fire safety regulations. We stock a wide range of CMHR grades, typically with densities of 25 to 60 kg/m3. |
| Convoluted Foam | Also known as egg-crate foam. This is a foam that has been processed with a special machine that presses a pattern of bumps into one or both sides of the foam. The result is similar to the shape of an egg crate. |
| HLB Packaging Foam | A type of packaging foam with a high load bearing (HLB) capacity. It can offer additional protection to various items and can be cut to create foam packaging inserts. |
| Recon Foam | Made from recycled scraps of foam that are bonded together to create a new recycled product. A durable foam used in bar seating, bar stools, church kneelers and gym mats. Also known as reconstituted foam or chip foam. |
| Reticulated Foam | A fast drying foam with wide open cells that allows water to rapidly drain through it. Has a visible mesh-like structure. Popular for making outdoor cushions and boat cushions. Our QuickDry grade offers much higher fire resistance than standard reticulated foam while keeping the same fast-draining benefits. |
| Upholstery Foam | A generic term used to describe various types of polyurethane foams used for upholstery purposes. |
| Viscoelastic Foam (Memory Foam) | A popular foam, often used in the manufacturing of mattresses and cushions to increase comfort. Viscoelastic refers to the foam’s ability to slowly return to its original shape after being deformed. |
Acoustic Treatment Terms
We’ve already covered acoustic foam, which is used to provide sound treatment for various types of indoor spaces. However, there are plenty of terms linked to this type of foam that you might not be aware of.
| Term | Definition |
|---|---|
| Bass Traps | Specialised panels that absorb low-frequency sound, preventing the bass from bouncing around the room. They are commonly placed in the corners of a room, where low frequencies tend to build up. |
| Decibel (dB) | The unit used to measure the intensity of a sound. |
| Frequency | The number of cycles of a wave that pass a certain point in each period of time. In acoustics, frequency is often measured in Hertz (Hz). Different frequencies correspond to different perceived pitches. |
| Hertz (Hz) | A unit of frequency representing one cycle per second. In the context of acoustics and sound absorption materials like foam, it denotes the pitch of the sound that the material can effectively absorb. Lower frequencies correspond to a lower pitch (bass sounds), while higher frequencies correspond to a higher pitch (squeaky sounds). |
| Noise Reduction Coefficient (NRC) | A scaled representation of the amount of sound energy absorbed upon striking a particular surface, ranging from 0 to 1. An NRC of 0 indicates perfect reflection, whereas an NRC of 1 indicates perfect absorption. |
| Pyramid Foam | A type of acoustic foam where the surface has been shaped into a pattern of pyramids. |
| Sound Absorbing Foam | Another name for acoustic foam, a specialised foam designed to absorb a percentage of sound wave energy to improve room acoustics. |
| Soundproofing | The process of preventing sound from entering or leaving a certain space. |
| Studio Foam | A general term for the foam used in studios for sound absorption. It comes in various styles including wedge, pyramid and egg-crate profiles. |
| Wedge Foam | A type of acoustic foam that has a surface pattern consisting of a series of protruding triangles in a wedge-like style. |
Units of Measurement and Testing
In order to determine its properties and suitability for various jobs, foams are tested under a variety of circumstances. There are many units of measurement used to describe each type of foam to help explain the benefits they offer.
| Term | Definition |
|---|---|
| Air Flow | A measure of the breathability of a foam, determined by the amount of air that can pass through it. It is often measured in cubic feet per minute (CFM). |
| Cell Size | A measure of the size of individual cells or bubbles in the foam structure, often stated in pores per inch (ppi). Smaller cell size can lead to higher strength and hardness, while larger cells can improve flexibility and shock absorption. |
| Compression Set | A measure of the extent to which foam retains its shape after being compressed. It is expressed as a percentage, with lower percentages indicating better recovery. |
| Density | A measure of the foam’s weight per cubic foot. This is often used to determine the durability of the foam, where low density foams will generally have shorter life expectancies when compared to high density foams. This is not an indication of how firm the foam is. |
| Indentation Load Deflection (ILD) | Also known as Indentation Force Deflection (IFD), it measures the firmness, comfort, or support level of foam by determining how much force is needed to make a 25 percent indentation on a 4-inch thick foam sample. ILD is often used in the mattress industry and is expressed in pounds force (lbf). |
| Shore Hardness | A measure of a foam or rubber material’s resistance to indentation, tested on a scale such as Shore OO or Shore A depending on how soft the material is. Used alongside density and ILD to describe how firm a foam feels, rather than how durable or heavy it is. |
| Tensile Strength | A measurement of a foam’s ability to resist tearing. It is usually expressed in pounds per square inch (psi) or kilopascals (kPa). |
Frequently Asked Questions
What’s the difference between open-cell and closed-cell foam?
Open-cell foam has broken cell walls, so air moves freely through the material, making it softer and more breathable. Closed-cell foam has intact cell walls, making it firmer and resistant to water and chemicals.
What is CMHR foam used for?
CMHR (Combustion Modified High Resilience) foam is used mainly in furniture to meet UK fire safety regulations. We stock a wide range of CMHR grades, typically with densities of 25 to 60 kg/m3.
What is Plastazote foam?
Plastazote is a closed-cell polyethylene (PE) foam blown with nitrogen, manufactured by Zotefoams. It’s water-resistant, insulating and lightweight, and it’s the closed-cell foam we stock and cut to size.
What’s the difference between foam density and foam firmness?
Density measures a foam’s weight per cubic foot and relates to durability, not firmness. Firmness is measured separately, for example through ILD or Shore Hardness testing. A high-density foam is not automatically firmer.
What is reticulated foam used for?
Reticulated foam has a wide open-cell structure that lets water drain through quickly, making it popular for outdoor and boat cushions. Our QuickDry grade offers even higher fire resistance for the same fast-draining outdoor use.
What does ILD mean for foam?
ILD (Indentation Load Deflection), also called IFD, measures how much force is needed to compress a 4-inch foam sample by 25%. It’s commonly used in the mattress industry to describe firmness and support level.
Have a Foam Question? Get in Touch
If you’ve got a foam-related question, we’ll be happy to help you. Our team of experts can provide a greater explanation of each type of foam we offer as well as the most common applications.
We always try to keep things clear and simple for our customers, but don’t forget to use this guide if there are any words you’re not quite sure about.
Cameron has emerged as a key marketing expert since joining GB Foam Ltd in 2017. A graduate of the University of Winchester, with a professional background in Public Relations; he has combined his content writing and brand awareness expertise with an in-depth knowledge of foam products and foam conversion technology to enhance the company’s marketing strategies and industry presence. Cameron has led numerous marketing campaigns, in both B2B and B2C segments, to further brand recognition and open up new business avenues worldwide.