An Article about

  Dye Systems
















You’ve successfully removed many stains using your favorite red stain remover. This time however, not only has the stain been removed but along with it some of the original color of the carpet. You’ve seen that pattern in upholstery fabrics before and it always cleaned up beautifully. After today’s cleaning the red from the flowers is beginning to bleed onto the white background. The yellow in the carpet looks like a urine stain. But, none of the urine stain removers in your spotting kit seems capable of returning this to the original color.


These are just a few of the many situations a cleaner will encounter where knowledge of fabric dyes and dye systems would be helpful.


Color sells carpet. The benefits of a resilient nylon fiber compared to the soft hand of wool or the stain resistant properties of olefin will be debated by cleaners, but Mrs. Average Home Owner buys her carpet because she likes the color and appearance. Her choice of color may have been influenced by the furnishings she will put into the room, the color of the walls or simple be a color she likes.


Manufacturers and retailers have long ago learned the importance of color when the buying decision is made. The successful cleaner should realize that maintaining or restoring the color will be important to how Mrs. Home Owner feels about the results of your work.


Dye problems can be a real challenge. You need all the expertise you can get. Many professionals use their expertise in spot dyeing and color correction to separate themselves from other cleaners. Understanding how mills dye the carpet we work on is a basis or foundation for being able to accomplish advanced color repair techniques.  We often use strong chemicals and even heat (such as in red stain removal) when cleaning carpets. We need to understand how chemicals and temperature interact with carpet dyes to avoid reversing the dye process and removing color or worse yet winding up with a hole where carpet used to be.

 

Dye Methods

Dyeing is the broad term for all methods of imparting color to fibers, fabrics, carpet and rugs. Dyes are colored materials that can be dissolved or dispersed in water or some other liquid. We will also talk about pigments which are solid particles of color that cannot be dissolved in water. They must be mechanically bound or locked into the fiber.


Numerous methods are available for the manufacturer to choose from. Each has it own advantages and disadvantages. What factors must be considered when deciding on a dye method? A process may yield excellent results when applied to one fiber but the result is less then acceptable when applied to another fiber. Cost, effect on the environment, design flexibility, availability of raw materials and necessary equipment, range of possible colors along with fastness to light and water are among additional considerations.

The color can be put supplied either before or after the yarn is tufted into carpet. When carpet is dyed prior to tufting the process is referred to as pre-dyeing.  Methods that apply the dye after dyeing are called post-dyeing.

Pre-dye methods include solution dyeing, stock dyeing, yarn dyeing, skein dyeing and space dyeing. Piece dyeing, Beck dyeing, use of a continuous dye range and various forms of print dyeing are all post-dye systems.

The more you are involved with high-end homes and corporate cleaning, the more likely you are to come across a greater variety of these systems. Learning to recognize each of these dye systems, learning how they can affect our cleaning efforts, and having advance knowledge of potential problems can really set a cleaner part from the run of the mill cleaners who take a one method fits all approach to their cleaning.

When we expand our view to include upholstery fabrics, the methods for creating color in or on the fabric skyrocket. We need to not only know how to clean but how to avoid problems and if you want to be the go to guy, you need to know how to solve color related problems.

This multi-part discussion will explain each of the dye systems, lay the foundation for color repair and open the door to new opportunities.
As a rule of thumb, the earlier in the manufacturing process that color is added the more stable the color will be. For example, solution dyed carpet is more resistant to strong chemicals, sun fading and so forth than carpet dyed on a continuous dye range. Yarn dyed carpet will be more resistant to the effects of traffic and cleaning chemicals than printed carpet.

If you can determine how a carpet was dyed you will know how aggressive you can be in your choice of chemicals or agitation. If the carpet constructed of solution dyed yarns your choice of cleaning agents could include any product intended for use on carpet and a few that are not. At the other extreme, you may want to suggest to the owners of some printed carpets that they be cleaned more often so that aggressive methods are not required.

Residential carpets are more commonly post dyed. This allows manufacturers to adjust to changes in consumer fashion trends without the need to stockpile huge quantities of yarn in every possible color.

Commercial carpet is more likely to be pre-dyed. Pre-dyed colors are better able to stand up to the rigors of heavy commercial use. However, many residential and commercial carpets are dyed using each process.

The yarns used in area rugs normally receive their color before being woven.  Solution dyed, yarn dyed or stock dyed fibers are positioned in their proper places by hand or by machine. Various treatments such as “tea washing” may be used after the rug has been completed to effect a change in the colors.

The variety of fibers and construction methods used for upholstery fabrics allows for a wide variety of dye types and procedures. Pre-dyed yarns may be woven into patterns. The cleaner will encounter many printed fabrics and occasionally a cross dyed fabric.

Cross dyeing is accomplished by combining several types of dyes in the same dye bath. When a blended fabric is submersed in the bath the various dyes have affinity for different fibers. Each fiber accepts some dyes while rejecting others. The result may be a multi-colored fabric dyed in one dye bath.

 Types of Dyes

Nylon is by far the most common carpet fiber we clean. Nylon is frequently gets its color from acid dyes. Most cleaners have heard of acid dyes and are even familiar with acid dye resistors used to impart stain resistance to nylon carpets.


As we continue to exam the variety of ways color can be added to all the products we clean, we should understand differences between pigments, basic dyes, disperse dyes, Azo dyes, natural dyes and more. Let’s begin by defining some of those terms as they apply to carpet and fabric dyeing.

Acid Dyes – are negatively charged ions in the form of salt. They easily dissolve in water. The pH level of the water will affect how readily they migrate (spread out or level), and how well they bond. pH may even affect the color. They are attracted to positively charged sites on nylon or wool. Acid dyes may also be used on silk. Food coloring is often an acid dye and so these colors often bond well with nylon and wool.

Azo Dyes – produce vivid colors in the yellow, orange, red hues. The name is related to specific nitrogen chemistry. Azo compounds may create acid dyes, disperse dyes or pigments.

Basic Dyes – are also water soluble ions but they have a positive charge. A key feature is brilliant colors they produce. Basic dyes may be used on natural fibers such as wool and cotton, but the colors are not very fast. You are more likely to see them used on acrylic and sometimes nylon and polyester.

Disperse Dyes – These are the only common dyes that will not dissolve in water. They are ground very finely and dispersed in water. Disperse dyes are used primarily to dye polyester and related fibers which do not absorb water and also being used for nylon and acrylic. The dyes are held in place principally by strong electric forces. These dyes are not affected by common cleaning agents, reducing agents, oxidizers or other chemicals used in cleaning. Some staining materials such as turmeric, a spice that gives mustard its yellow color, act as disperse dyes making such stains very difficult to remove.

Fluorescent Dyes – Fluorescent dyes will fluoresce or glow under ultraviolet or black light. Due to the properties of the dyestuffs, some manufacturers do not warranty the color. Fluorescent dyes are sensitive to sunlight. The dyes are adversely affected by alkaline cleaners. Whether cleaning or spotting these carpets it is important to use only cleaning agents on the acid side or near neutral on the pH scale. Because these carpets may be heavily soiled but must be cleaned with mild cleaning agents it is important to have reasonable expectations of the results. Fluorescent dyes are often applied by the print method.


Optical Brighteners – These are a type of dye with a chemical make-up that absorbs energy in the UV range and re-emit it in the visible range, usually as blueish white. They are sometimes adding to carpet cleaning products to make carpet appear brighter and cleaner after cleaning. With time and exposure to light, they can give carpet a yellow or brown color. Most major carpet manufacturers specify that the use of optical brighteners will void the warranty.

Natural Dyes – The earliest dyes, these came from plant sources including leaves, roots and bark of trees, minerals and insects. When discussing hand-knotted rugs made of natural fibers, natural dyes may also be referred to as vegetal dyes. The colors tend to be muted and earth tones. They are suited for natural fibers including wool and cotton, but not often used for dying synthetic fibers.

 The Process – Pre Dye Systems

Color may be applied at many stages of the process from the fiber to the finished carpet.
Some processes apply the color before the yarns are tufted into a carpet. These are classified as pre-dye methods. We will now take a closer look at some of the pre-dye methods.
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 simply 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, slightly lighter colors 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 – Being prepared to fill 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 not a large 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 PROCESS
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 or fiber 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 moved through the fibers to reach all surfaces, thus 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 dye is a broad term that describes several processes where the color is added after the fibers have been spun into yarn. Package dyeing is one type of yarn dyeing in which the yarn is wound into packages or onto spools and suspended in the dye bath where the liquid circulates around the packages of 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 cannot 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 single yarns 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 long sock but with both ends open. 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 have you seen 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 encourage them to view you as the carpet expert and earn 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 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 discoloration 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.

Post Dye Systems
If pre-dye systems have the advantage of greater colorfastness and evenness in coloration, why is so much carpet post-dyed?
Thousands of yards of residential carpet are sold because Mrs. Home-Owner likes the color. Some colors have been perennial favorites, forest green for example. But many color choices are affected by designers and photo layouts in popular magazines. The color choice that was all the rage last fall may be out-of-style this spring.

It simply does not make economic sense for a manufacturer to fill huge warehouses with every style of carpet in every possible color. Sooner or later they would get stuck with 10,000 yards of Pumpkin Spice frieze (which everyone knows is now out of style).
It requires much less warehouse space to store greige goods (undyed carpet). This carpet can then be dyed to match needs thus saving lots of expense that would otherwise be tied up in inventory and building warehouses.
Post-dye systems also allow for small custom runs to suit a particular consumer. For example a business would like its logo displayed in the lobby carpet or maybe a university wants carpet in the school colors or a designer needs a particular shade to accent the living room she is designing for Mrs. Piffleton.


Piece Dying refers to dye systems applied to an entire piece of carpet. Major piece dye methods include Beck dying and use of a continuous dye range.


Beck Dye Method – Lengths of carpet are connected end to end to form a large continuous loop. This carpet is placed in a large vat called a beck. Rotating reels in the beck move the carpet in and out of the dye liquor. Heat and pressure can be added to assure that the dye penetrates deep into the fibers.
Beck dyeing results in an even coloration from one end of a piece to the other. However the size of the vat limits the length of the carpet roll that can be done at one time. Dye lot variations will exist from one roll to the next. For this reason, beck dyeing is more often used for moderate sized runs in specific colors.
After being removed from the beck, the carpet will be extracted and dried. The secondary backing is then applied and the carpet goes to the finishing stages of production.

Nylon and polyester may be beck dyed.


Continuous Dye Range – A conveyor system moves the carpet through the dye application, steaming to set the dye, a bath to wash off excess dye and a dryer. Continuous dye ranges are widely used because they can handle large volumes of carpet quickly and inexpensively.
In the pad dye variation of the continuous dye range, the greige goods are routed through a trough containing the dye. Heavy rollers then squeeze the carpet to spread the dye out evenly and remove excess liquid.
In the more popular Kusters (Rhymes with boosters) dye range the carpet passes under spray jets, foam dispensers, drips or rollers that apply the dye. This allows for a greater variety of design effects.  For example, if the dye is applied as foam, the color will be a deeper shade on the top of each tuft becoming lighter toward the base of the shaft.  A dye resist can also be applied prior to the dye to produce variations in the color.
Polyester and nylon fibers are also suitable for the continuous dye methods.

Print Dyeing – Print dyeing allows for specialized and customized designs to be applied to carpet.  This works great for corporate logos and similar applications.  Additional decorative effective may be added to a carpet that has the main color field dyed using another process.
There are several variations of this method.  With screen printing a fine screen is created for each color to be used. Ink is forced through the screen with squeegees as the carpet passes underneath. Some machines allow as many as 8 different colors to be applied in succession. Lighter colors are applied first. You may be familiar with this method if your name or logo applied to your uniforms by screen printing.

Rotary printing is similar. Think of the flat screens being bent to form a tube.  Like printing a newspaper (remember those), carpet passes through a series of rollers with pattern screens. Dye is pushed through openings in the rollers by a squeegee inside the roller. On engraved rollers a doctor blade scrapes off excess dye to provide an even application.

You will be able to recognize a print dyed carpet by looking at a side view of the tufts. Color will be heavier at the top of each tuft and usually will not reach all the way to the base of the tuft. Sometimes a print will be applied on top of an already dyed carpet to complete a desired look.

Since the color is not forced into the fibers it will be more easily removed than any pre-dye method or any of the previously mentioned post dye processes.
I have seen the printed portion of a pattern coming off during restorative cleaning using alkaline chemistry and mechanical agitation.


Ink Jet or Injection Dye is applied by spraying the color on in patterns in a fashion similar to an ink jet printer. Precision control of the carpet and jets allows for the use of rather fine and intricate designs.
Ink jet or other print dyes are more easily harmed by strong cleaning chemicals or the wear and tear of high traffic.

Print dyes are applied mainly to acrylic and nylon but can be used on almost any fiber.
The Latest Innovation is not actually a dye system, but technology for using already dyed yarns (often solution dyed yarns). It is known as computerized yarn placement or CYP for short. This allows multiple colors of yarn to be placed anywhere in a pattern by computer control. It is possible to scan a photograph or other source and the software will guide the tufting needles to duplicate the pattern. Even a single carpet or rug can be created by this method, thus allowing great freedom in producing custom made rugs and carpet.


Although not used for carpet, patterns may be placed on upholstery fabric by heat transfer. Designs are on sheets placed over the fabric. The fabric and design sheet pass between heated rollers the force the color off the sheet and onto the fabric. The process is much like iron-on or heat transfer patterns that may be put on a T-shirt. If you have such a shirt and have laundered it several times, you get an idea of how well this holds up compared to the colors dyed into the fibers.  Wear, multiple cleanings and aggressive chemicals can all contribute to loss of these patterns.

Because of the huge role played by color and design in the sales of carpet, we can expect to see innovative new technology as well as innovative uses of existing technology. Being aware of dyes and dye systems used in your client’s carpets will add greatly to your credibility as a cleaner. This information will also alert you to proper chemicals and procedures to use on each carpet you encounter.