Joint Industry Foam Standards and Guidelines


Published: 7/94

Effect of Cover Fabric on Cushion Firmness

Many of the sources of complaints on firmness or softness of cushions are associated with something other than variations of foam IFD. One of the single largest and most significant sources of problems of this type is upholstery fabrics.

Fabrics affect firmness - but the exact magnitude of the effects is not known. The following table demonstrates quantitatively, the effect of this group of upholstery fabrics on final cushion IFD. Data in the table was derived as follows:

24" x 24" x 4" thick foams with IFD's measuring 26 pounds, 27 pounds, or values between 26 and 27 pounds only were used in the test. (All IFD measurements were made in a conditioned lab by the same technician). Foam cushion cores were 24" x 24" x 4", and the foam was wrapped with 1.1 Oz/square yard, resinated polyester fiber with 1.5" measurable loft. All polyester fiber came from the same roll and was allowed to relax under zero load (uncompressed) for 36 hours prior to cushion wrapping. Two inches of the entire horizontal periphery of the foam cushion cores were sprayed with adhesive to prevent rolling or moving of the polyester while the cushion jacket was being stuffed with the core plus polyester wrap.

Each upholstery fabric used in the experiment was cut and sewn as follows:

  • Top and bottom panels---24" x 24" (then sewn with 0.5" seam allowance)

  • Boxing strip---4.5" wide(then sewn with 0.5" seam allowance)

  • The experimental cushions were boxed, non- welted, zippered cushions

A standard pile fabric was chosen based on general softness-pliability; ease of sewing without wrinkles, puckers, etc; and breatheability. All other fabrics were compared to the standard. After the cushion jackets were cut, sewn, and stuffed, a type of IFD was run as follows: The finished height of the cushions was measured in the exact center of the cushion by using a one pound pre-load. The cushions were then flexed twice to 75% of their total, original measured height using the indentor foot and a vertical speed of 1.0 inch per minute. the cushions were allowed to rest for 10 minutes plus or minus 5 minutes before further testing. After the rest period, the finished cushion height was measured with a one-pound pre-load, and the indentor foot was indented into the cushion exactly 1.25" at a vertical speed of 2.0"/minute. After one minute, the force required to accomplish the deflection was read in pounds and recorded. Data thus generated is a follows:

  • The Effect of Upholstery Fabrics on Cushion IFD Fabric Description
  • 1.25" IFD(in pounds)

  • Standard Velvet 31.5

  • Sliver Knit(14% Elongation) 29.0

  • 8.4 Oz/ydý Cotton Print (warp satin) 32.0

  • Raschel Knit Velvet (Mayer Type) 32.0

  • Tufted Velvet 30.0

  • Woven, Textured Flat (With Air Textured, Spun, Chenille, and Monofilament Yarns) 45.0

  • Weft Insertion Knit (With Spun, Boucle', Air Textured, and Chenille Yarns) 43.5

  • Printed Flock 41.5

  • Flat Jacquard (double cloth tied-down construction) 49.5

  • Flat Woven (with large diameter spun yarns adjacent to very small diameter spun yarns and then latex backcoated to accommodate the large degree of heterogeneity in yarn size) 54.5

  • Vinyl Fabric (with breather strip sewn on one side of cushion) 50.5
Note: With the exception of the printed cotton and the vinyl fabric, all fabrics were backcoated.

Fabric construction and yarn type alone are not totally responsible for the increase in finished-cushion, equivalent IFD. Latex backcoating applied and/or selected improperly can even spoil the softness and suppleness of the standard fabric. Suffice to say, however, fabrics do contribute significantly to the firmness-softness of seat cushions; and complaints should be thoroughly reviewed before core foams are deemed to be at fault.