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The Truth about Dust Bunnies

by: Verde Home 2/24/09


If you have ever owned a wool area rug, chances are you know about or have at least witnessed a “dust bunny”.  Dust bunnies are the urban equivalent of interior tumbleweeds.  They start as small clumps of wool, lint, and dust emanating from the surface of a rug and before you know it you have a softball sized “pom pom” clinging to your floor.  But how do these little critters form, and why do some rugs seem to produce dust bunnies like it’s their job?

 
Both Paul and I have been in the rug business for a long time and are very familiar with the effect.  We can usually point out rugs that will tend to shed more than others but until now we have not explored the technical reasons for the effect.  With several clients asking us about this phenomenon as of late, particularly in regards to tufted rugs purchased through chain stores, we felt it was time to do some in-depth research to get to the bottom of this once and for all.


First off let’s define what dust bunnies truly are.  The technical term for what is happening is called “pilling”.  Almost all natural and manmade fibers will pill to some degree or another.  Pilling occurs when individual fibers (wool in the case of most rugs) either pull out or break off of the yarn tuft that they have been spun into.   These fibers rise to the surface where they gather and ball up due to static electricity.  The degree to which this will happen is a matter of several technical factors but it all basically boils down to two simple ones; the quality of the wool fiber used to make the rug and the durability of the construction method used to “weave” the rug.  Let’s take a look at each factor individually before discussing how they combine to cause pilling.


Wool Quality

The soft pile that we feel in a wool rug is a spun yarn, made by twisting the straightened wool fibers into a long continuous thread.  Wool is naturally a staple fiber meaning that it grows in clusters that are interlocked by cross fibers.  After the wool is sheared it is graded to determine value and best use.  This grading system is complex but generally relates to the length of the wool staple, staple strength, the thickness and crimp of the fiber, and what time of year it was sheared  (sheep sheared in the spring have had all winter to grow a thick coat resulting in a denser, longer and stronger staple).  Higher grade (and more expensive) wools tend to be those of longer staple length that are strong and clean, with uniform coloration and a fine crimp.  The coarser, strong, and longer staple wools (higher grade) make the best rug yarns as they hold up better to the constant surface abrasion of walking, while the finest crimp wools are most often used in garments as they can be spun into very fine yarns.


Construction

Before we go into how wool quality affects pilling, lets first look at construction since they go hand in hand. The two most common methods for constructing wool area rugs are tufting and hand knotting.  Tufted rugs are produced by inserting a yarn into a separate prefabricated base material, much like a mesh.  The inserted tufts are then secured to the base using an adhesive (often latex).  The basic process for making tufted rugs is essentially the same regardless of whether it is made in Dalton, GA or New Delhi, India.  The major difference between the two is essentially the speed in which they are created.  Modern tufting factories like those in Dalton run the base material through a large machine that inserts the yarn tuft followed by the adhesive in one incredibly efficient continuous process.  Pieces produced in India and China (the two most common sources for Hand Tufted rugs) are tensioned on a rack before the tuft is injected.  An interesting point worth noting is that virtually all “Hand Tufted” rugs are actually machine made.  The machine that injects the tuft into the wool must be held by hand so it is sold as a “handmade” product, but about the only time a hand touches it is when it is put on and taken off of the tensioning rack (click here for video link).


Hand knotted rugs, as the name would imply, are woven by hand with each individual knot being tied to an interlocking web of warp and weft strings that are wrapped around a loom (for information on the types of knots used and weaving detail please see our library article entitled “Why Knot?”).  The result is an incredibly sturdy and flexible textile.


Why so shaggy

So how do these two factors combine to create a rug that sheds?  Let me first say that all things equal, a tufted rug is more likely to pill excessively than a hand knotted rug.  But why?  Let’s look at how the above factors come into play.
Most tufted rugs are produced with cost as the primary concern.  The mechanization greatly reduces the labor cost, however in order to save more, the rugs “hand” tufted in India and China are made from a cheaper local source of wool (coming from sheep that have been bred with Merino’s).  This wool has a shorter, dryer staple and a high lanolin content (oil naturally occurring in the wool) which requires aggressive cleaning prior to use.  The naturally shorter staple length combined with aggressive cleaning results in a fiber more prone to breaking.  As these fibers break off they collect on the surface contributing to the pilling effect.


A second area where costs can be saved is found in the adhesive backing.   Every yarn tuft that protrudes through the base material is called a “tuft bundle”.  In order for the tuft bundle to remain intact it must be completely covered in adhesive.  Many producers are willing to trade off a bit of speed and cost in exchange for quality, which has lead to an industry standard of 80% coverage becoming the norm.  The 20% that are left uncovered will rapidly release from the backing and collect on the surface.  As the backing adhesive becomes dry and brittle over time, it too can crack and slowly release the yarn tufts to the surface.


Because the labor involved with a hand knotted rug is so much greater (often taking months rather than minutes), these rugs have an intrinsically higher base cost resulting in a more expensive product.  Producers tend to spend more on raw materials in order to make the piece stand out and justify the greater price.  In order to do this, weavers often choose higher grade wool (longer staple, less brittle).  In fact most handwoven rugs from Turkey, Nepal, Pakistan or Afghanistan are made using wool from the indigenous long tailed sheep which naturally produce longer, dense staple wool that is ideal for rugs.  This wool, once spun into a yarn, is knotted to the foundation and becomes very difficult to pull out unless the foundation becomes rotted or torn.  Individual fibers will still break off and cause some initial pilling but this effect will lessen with time.  The combination of better wool with sound construction means that the rug will be less prone to pilling.


You get what you pay for

As with most things, the old adage that “you get what you pay for” also holds true for rugs.  Cheaper rugs cost less because they are made quickly, using lower grade wools.  These wools tend to be dry, shorter staple and more brittle.  Over time, the short dry fibers break and release from the foundation and come up to the surface.  Handwoven rugs are costly to produce and tend to use higher grade wool.  This wool is less prone to breaking or releasing to the surface. As a result they pill less.  No rug will ever be completely impervious to shedding, but if you can’t stand vacuuming up wool tumble weeds, a hand knotted rug is a good place to start.


Special Thanks

 


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