There is a lot of misconceptions when it comes to density and firmness of polyurethane foam. If you google this, you will come across a number of websites where they speak differently on these two things. If you are in the USA, density is the firmness of the foam. So, that makes these two words interchangeable if you are in the USA.
However, in Canada, they are two separate tests and allow for a lot more information to help guide your decision making. So, let's begin!
Density is the physical weight of the foam. This is rated as pounds per cubic foot. The higher the number, the better the quality of foam, and the longer it will last especially if it is in a high traffic area. Density can be as low as 1 lb/cubic foot and go up to 8 lbs/cubic foot. More on this in a bit!
Firmness, on the other hand, is how hard (or soft) the foam feels. This can vary from a very soft firmness of just 12 lbs to extra firm of 99 lbs. This test is done with actual weights where they use a 4" piece of foam, 12" x 12" and put various weights onto the foam. Whatever weight indents the foam 25% (or 1" in this example), tells us the firmness. So, for a foam that has a compression rating of 38 lbs, that means it takes 38 lbs to indent the foam 25%.
So, with the terms defined, it is also important to realize that just because a piece of foam is firm, does not mean it is of a high quality. You are able to purchase firm foam that is not great quality and will collapse very quickly under regular wear and tear. Just as it is possible to get a very high quality foam in a soft feel. And how do you make this choice? At the end of the day, the biggest choice you have to make is the density/quality of the foam. Once you know that, then the firmness is simply a personal choice (ie do you like to sit on a soft cushion or a firm cushion?). Pricing is always linked with the quality of the foam. So the higher the density, the more money you are going to spend. However ! That also means it will last much longer. The old saying is true here - You get what you pay for!
Here are some guidelines on making sure you are picking the right density foam for your project.
A 1.0lb density foam is great for padding a wall, hallowe'en costumes, padding in the arms/backs of a piece of furniture, or anywhere there will not be much if any weight or wear and tear.
A 1.7lb density foam is basic commercial grade quality. This works well in furniture that would be more for looks than use. It can take some wear and tear, but if used regularly will collapse within a couple of years. It does work well as a mattress in a hunting or fishing camp that is seasonal use.
A 2.0lb density foam is a great one for seating in furniture, window seats, dining room seats, etc. It can take a lot of wear and tear and hold its firmness. It is also ideal for mattresses in homes and cottages. This foam typically has a life span of 5-8 years.
A 2.5lb density foam is the best quality open cell foam you can purchase. This is ideal for restaurant seating, or residential furniture that gets a lot of wear and tear, or as a mattress that you want to last 10-15 years.
So what does this mean at the end of the day? Make sure you are spending your money wisely and know exactly what you are buying. If someone tells you it is high density foam, you now know they do not know what that means so be proactive to get the real answer. Information is key and we want you all to stay comfortable out there