An earlier post in this series briefly covered a few of the various methods used to dye carpets. This article will take a closer look at some of the pre-dye methods. These are processes apply the color before the yarns are tufted into a carpet. A future topic will go into more detail about continuous range dyeing and print dyes which are applied after the fibers have been tufted into carpet.

Names applied to some of the pre-dye systems include solution dying, stock dyeing, skein dying and space dyeing.

Advantages of Pre–Dye Systems

• Colorfastness - In general pre dyes will exhibit greater fastness to light, washing, chemicals and even oxidation due to age. The dye stuff or pigment penetrates the fiber more deeply than post dye methods.
• Evenness of color –Dye lots of almost unlimited size and uniform color can be produced by solution dyeing. Staple, pre-dyed fibers can be blended. This allows the color to be even. This is especially important in larger open areas that can be found in some commercial settings.  Whether natural or synthetic, some fibers simple accept more color than other similar fibers. There will also be variations from one dye lot to another. By blending fibers from several batches of fibers, yarns that may be a slightly lighter color are mixed with some that may be slightly darker. When the yarn is tufted the result is an even color that would be difficult or impossible to achieve with post dye methods.
• Design Effects – Space dyeing in particular offers the appearance of a more random pattern than is achieved with most post dye methods. Computer yarn placement is a post dye method that can be an exception.
• Solution dyeing does not produce the large volume of waste water and dye that is standard with other methods. Solution dyed yarns are also easier to recycle.

DISADVANTAGES

• Less Flexibility in color choice – Fulfilling any order that might come in with pre-dyed yarns in any of the thousands of colors carpets are sold in would require a huge warehouse full of yarns. Since this is impractical the color choices in pre-dyed yarns are limited.

           In the case of hand woven rugs made of natural dyes from vegetal and insect sources, there simply is a limited selection of colors available.  For example Green is rarely seen in naturally dyed rugs. Lacking a good green dye, the yarn must be first dyed blue and then a second application of yellow.

• Cost – The processing of pre-dyed yarns usually increase the cost of the final product.

DESCRIPTION OF EACH METHOD

Solution dyed yarns get their color from solid pigments mixed with pellets of polymer before it is extruded. The color is blended throughout the entire fiber. This can be compared to the color seen when one cuts a cross-section through a carrot. With other dye methods most of the color is on the outside similar to the cross-section of a radish with red outside and the white center.

Because olefin fibers absorb very little moisture and have no sites where dyes can easily be chemically attached, olefin fibers are solution dyed. Some nylon fibers are also solution dyed.

The Stock Dye method is used for staple fibers before they are spun into yarn. Wool is frequently stock dyed. Acrylic, intended to imitate wool, may also be stock dyed. Fibers are placed in a large vat where color is added using heat and pressure.

The dye is able to reach all surfaces of the staple fiber applying the color evenly. Fibers from several batches can be blended before they are spun into fiber. This permits the manufacture of large volume of fibers with even, consistent color.

Yarn dying is a broad term that describes several processes where the color is added after the fibers have been spun into yarn. Skein dyeing and space dyeing are the two most common methods that fall into this category.

Skein dyeing is similar to stock dyeing. In the case of skein dyeing, fibers have been spun into single ply yarns and wound onto skeins. The skeins are then placed in a vat. Dye liquor is added to the sealed vat under heat and pressure. Because several batches can not be blended together, this produces smaller quantities of a solid color yarn than the stock dye method. These small batches make skein dyeing a good choice for custom colors.

Following skein dyeing the singles will be twisted together to form multi-ply yarns and then tufted into carpet.  Skein dyeing will also be used for the yarn in hand-knotted rugs. Fibers commonly dyed this way include wool, acrylic and nylon.

Another yarn dye method is known as Space dyeing.  Bulked continuous filament (BCF) nylon fibers are knitted into a tube or cylinder like a sock but without the toe end. Several colors are then sprayed on or applied with rollers. The sock is de-knitted back to a yarn that now has bands or streaks in 2 or more colors. The color placement appears to be random. When tufted into a carpet, it has a mottled or heather look. Space dyeing is used in many commercial level loop products.

Some solution dyed nylon and occasionally stock dyed acrylic are found in residential wall-to-wall installations. Olefin (solution dyed) is widely seen in both residential and commercial goods. Wool area rugs are commonly stock or skein dyed. However, the majority of pre-dyed fibers go into commercial products.

Why are some settings a great match for pre-dyed products? The hospitality industry (hotel and restaurant chains) and corporate office buildings plan carpet changes on a regular schedule well in advance. They use relatively few colors across many properties. The popular trends don’t change frequently. For example, how often do you see forest green or deep red dominate the large patterns in a hotel hallway? These businesses want the color stability and durability. Institutional carpet cleaning may be handled by staff members who have limited training in carpet cleaning. Chemical resistance and fastness to washing is a plus in these situations.

Why Does the Cleaner Care?

Your potential client is making a decision on whom they will allow into their home or business and entrust to clean their valued possessions. Being conversant with the construction of their carpet goes a long way to earning their trust.

Knowing the dye system used also lets you know what cleaning methods and chemicals can safely be used on a particular carpet. You’ll also be better able to identify causes of color related problems.

You’ll also gain confidence in your ability to handle carpet produced using any dye system that comes your way.

Solution dyed carpet can withstand any chemical in your spotting kit plus a few that may not be in your spotting kit.  Any color change is unlikely to be fading or color loss. More than likely it can be removed by cleaning.

When you encounter a large room of a single color you’ll be alert to the possibility of stock or skein dyed staple fibers. Aggressive agitation could cause fuzzing.  These fibers could be wool, acrylic or nylon. A burn test will tell you if this carpet can be treated like a synthetic or wool.

BTW- If you would like a flow chart style burn test chart, send me an email with burn test chart in the subject line and I will be glad to send you one.

Scott Warrington has over 40 years experience in carpet cleaning. He currently serves as the Director of Technical Support for Interlink Supply and Bridgepoint Systems.