The Purpose of this webpage is to educate you about foam cushion materials which are used in furniture. There are many different grades of foam that are available to the Upholsterer. This webpage will explain the rating standards for foam material so that you will have a better understanding of what makes a particular foam suitable for various applications. There are not necessarily "good" foams and "bad" foams. There are, however, good and bad uses for each particular type of foam which determines your level of satisfaction and comfort with your furniture.
If your foam cushion material is older than about 10 years, or if it is beginning to have a "rounded" front edge, or if the seat foam doesn't offer you the support you need to feel comforatable, then you are probably ready for new foam. Foam production technology has made some very significant advances in the past decade. Foams of varying densities and ILD ratings are now produced which offer the Upholsterer an opportunity to select a specific type of foam based upon its intended use. Foam is rated according to various performance tests. The results of these tests allow an Upholsterer to know how the foam will "feel" and in what ways the specific foam may be used.
I mentioned the "rounded" front edge as a clue to the need for new foam. This effect occurs over time because you tend to use the front of your cushion to a greater degree than the rest of the cushion. As a result, that portion of your cushion becomes worn or compressed faster than the rest of the cushion. Some Upholsterers will use their steamers to restore the foam to its original shape but this is only a temporary fix and the foam will soon loose its shape again. Another cause for this condition is that the foam never was the proper density to be used as seating foam and as a result it has lost its shape in a relatively short period of time.
There are three performance tests that are of primary concern in evaluating the suitability of foam. The first concern is if the foam is rated as HIGH RESILIENT (HR). The next concern is the DENSITY rating of the foam. And finally, the INDENTATION LOAD DEFLECTION (ILD) rating is of equal importance as the foam's density rating.
HIGH RESILIENT (HR) foam is what you might think it is. It is a foam material that is produced to offer a longer useful life than non-HR foam. HR foam is often also rated as fire resistant (FR). Tell your Upholsterer that you are concerned about fire safety and long life of your new foam and ask him to verify that your new foam is rated both HR and FR. If you are reupholstering furniture which will be used in a public setting, most States have Furniture Flamibility Laws that will require you to use HR-FR foam materials.
The DENSITY rating of furniture foam is expressed as a two digit number which may range from 18-35. Actually, there is a decimal between the two numbers which makes the density rating of the #18 foam a 1.8 foam. In the production of foam, there are two basic ingredients which are the urethane chemical that is the foam, and air. The more chemical that exists in the foam material, the higher its density rating will be. In the above example, the 1.8 rating means that there is 1.8 pounds of chemical in each cubic foot of foam material. A cubic foot is equal to an area that is 12" x 12" x 12". This particular foam would be rather low in density and would not be a good material to use in seat cushions. It would, however, be suitable for back cushions as back cushions do not need to support your body weight as seat cushions do. Most people prefer the comfort of a low density foam in their back cushions for the soft feel that allows them to "nest" into their chair.
The next rating of concern is the INDENTATION LOAD DEFLECTION (ILD) rating. This is a measure of how much pressure it takes to compress the foam 25% of its thickness. For instance, if your seat cushion is 4" thick and has an ILD rating of 33, it would take 33 pounds of pressure to condense the foam to a thickness of 3". In normal operations, most shops prefer to use a foam with a density rating of 3.1 and an ILD rating of 33 for sofa and chair cushions. They'll usually use a back cushion foam which is a 2.4 density with an ILD rating of 18. This foam material produces a medium-firm back cushion. Where a softer back cushion is desired the 1.8 density/ 11 lb. ILD foam material may be substituted.
On dining room chairs, where the thickness of the foam is generally lower (1-2"), it would be recommended to use a foam with a density rating of 2.8 and an ILD rating of 41 to compensate for the reduced foam thickness. Where some reupholstery clients prefer the softer feel of the 33 lb. foam for dining seats, It is usually recommend increasing the foam thickness by 1/2" if the chair style lends itself to that option.
Below is a chart which describes some of the different foam materials. Notice how an entirely different ILD rating can be produced using a density rating in the 2.7-2.8 range. This should illustrate the importance of the ILD rating in selecting a suitable foam for your needs. A high density foam is not necessarily the proper firmness.
You will note that the ILD ratings of the foam materials in the chart range up to 61 lbs. While these very firm foam materials are available and have their specific and appropriate uses I would never recommend the use of any foam material higher than a 41 lb ILD rating for seat cushions. The 50 and 61 lb ILD foam materials may be used for such applications as kneelers or fitness equipment pads where the foam thickness is limited to 1-2" and the higher ILD rating is necessary to compensate for the limited thickness of the foam.
|11||1.8||Extra Soft||Soft back cushion, envelope feather/down cushion|
|18||2.4||Comfort Soft||Firm back cushions, XX-Exta soft seating|
|26||2.7||Soft||Extra firm back cushions, Soft seating|
|27||2.8||Medium Soft||Medium soft seating|
|31||2.7||Medium||Medium seating.(Exceeds industry standards)|
|33||1.9||Medium Firm||Medium firm seating|
|33||3.1||Medium Firm||Medium firm seating|
|41||2.8||Firm||Firm (2" Dining chairs)|
|50||3.2||Extra Firm||Extra firm seating|
|61||3.0||Extra Firm||Extra firm seating|
Cushion wraps are a layer of material that is installed between the foam material and the fabric cover. A commonly used cushion wrap material is DACRON. It is commonly recommended to use as cushion wrap and is further recommended that the dacron material be laminated to the foam using special foam glues.
The purpose of the dacron wrap is to soften the sharp edges of the foam to give it a more soft appearance. The dacron wrap also helps to protect your fabric in the event of a liquid spill by allowing the liquid to pass through your fabric and the dacron and settle in the foam. While the spill may keep your foam wet for several days, there will be a barrier between your foam and your fabric which will allow your fabric to dry out rather than continue to soak up the wetness from your foam. Even a dry spill,such as dirt, will have less of a soiling effect on your fabric with a dacron wrap as the dirt will pass through the dacron to some extent and not be ground into your fabric as much. Another advantage of a dacron wrap is that some foams and fabric backings are somewhat abrasive. Each time you get into, or out of, your chair the fabric and foam rub together to some extent. The dacron wrap will eliminate this abrasive action and extend the life of your fabric and/or your foam. The dacron wrap should be laminated to the foam to prevent the dacron from moving and bunching up inside of your cushion cover. A laminated dacron wrap will likely increase the cost of your foam cushions, but should be considered a good investment.