Denim Wet Finishing

Denim Wet Finishing Overview

 

The special character of indigo-dyed yarns offers garment finishers many opportunities to enhance basic denim. One way is through wet processing, which encompasses two techniques: garment washing and garment wet finishing.

 

Sometimes the terms are used interchangeably but there are differences:

 

  • Washing refers to cleaning impurities from a substrate or removing processing aids.
  • Finishing refers to any process other than preparation or coloration that gives a fiber, yarn, fabric, or garment useful or desired characteristics.
  • Garment washing can be as simple as removing dirt, oil, grease, or sizing materials from a garment. It may also involve bleaching, enzyme treatments, discharge processes, or overdyeing or tinting.
  • Garment wet finishing involves using abrasive agents such as natural stones or chemicals to alter the appearance of the fabric. This might involve removing color, producing contrasting effects, or softening the fabric surface. Wet finishing also includes chemical softening, cross-linking of chemistries or resins, or other technical chemistries.

 

Popular names given to various wet finishing techniques include stonewash, frosted, snow wash, sand wash, powder wash, galaxy wash, acid wash, electric wash, ice wash, midnight wash, shotgun wash, earth wash, pearl wash, galactic wash, antique wash, and whitewash.

 

Some of these terms describe a specific garment appearance, some refer to a specific garment processing sequence, and some are used mainly for market identity. While they may have once been proprietary, many of these terms are now considered generic and interchangeable by producer, retailer, and consumer.

 

 

Washing & Wet Finishing Techniques

 


 

Desizing/Washing

Desizing denim jeans is necessary to remove the sizing compounds that are applied to the indigo warp yarns prior to weaving. Once the yarns are woven into the fabric, the sizing compounds tend to make the denim harsh and rigid, and they can interfere with subsequent chemical treatments.

 

The method used to remove warp size depends on the type of sizing used. The most common sizes are starch, PVA, CMC and various binders, waxes anti-stats, and other weaving aids.

A typical desizing process involves loading the machine at a ratio of 8:1 of water weight to fabric weight and using a non-ionic detergent, moderate temperature level, and two to three rinses. If the sizing includes starch, an enzyme is also added to the treatment.

 

Many consumers prefer darker denim shades that have not been washed down severely. These types of washes are usually referred to as rinse washes because they use a chemical rinse to soften the fabric and fix the color. One example is the dark rinse. Typically a rinse wash consists of desizing, softening and top brightening without an abrasion step, using a cross-linker helps to better retain color. If a rigid hand is desired, the desizing step is omitted which also helps to retain the shade

 


 

Abrasive Color Loss

Stonewashing

 

Stonewashing is a technique used to accelerate the fading and softening of denim jeans by adding pumice stones to the wash. The stones can be natural or synthetic, in different sizes or shapes, producing varied effects.

 

The natural pumice stones used in stonewashing are mined and produced in various grades. Pumice is mined around the world in places such as New Mexico, Turkey, Ecuador, and Italy. Due to shipping costs, most of the United States uses domestically mined stones.

Pumice stones range in size from a marble to larger than golf balls. Grades are measured in size by inches and also by their abrading ability. The effect of pumice stones on fabric varies depending on the size, abrasiveness, and volume of stones used per pound of garments. The type of pumice and its mining method affect the size, weight, strength, porosity, and absorbency of these stones.

 

The rate of attrition, or how long the stones last, depends on the mechanical action of the washing process, the brittleness of the stones, and the desired effect. Pumice stones work by cutting or abrading the surface of the fabric. The grit from the stones sands, scrapes, and cuts the yarns in the fabric and the edges and folds of the garment. Both fiber and dye are removed and the surface becomes softer. The result is an attractive, unevenly dyed appearance that looks faded or aged. Smooth stones yield a more even effect while rough stones provide a more distressed look.

 

 

Stonewashing Process

 

Let’s look at a typical stonewashing process. On average a pair of jeans weighs two pounds, a stonewashing run of 100 pounds of jeans uses 250 pounds of pumice stones and 140 gallons of water for a period of one hour. Then there are more intense stonewashings which can last from four to six hours. Jeans about to be stonewashed may first be subjected to other finishing techniques such as hand sanding or potassium permanganate processing, then they are loaded into a belly washer but they still may not be ready for stonewashing. First, any necessary preparation procedures such as desizing must be performed. Once all preliminary procedures are done, then the stones are finally added to the belly washer. Stonewashing requires exact ratios to achieve a controlled and localized abrasion.

 

Several factors must be taken into account such as:

 

  • Stone ratio: Typically, the more stones per pound of garment, the greater the abrasion.
  • Liquor ratio: The higher the liquor ratio the lighter the abrasion
  • Washer diameter: A larger machine diameter means greater machine capacity and higher productivity
  • Load size: This is determined in large part by the machine capacity.
  • Chemicals: The garment fiber composition and the desired level of abrasion dictate the amount and type of chemicals used.
  • Drum speed: Along with the tumbling action of the garments and stones, the speed of the drum directly affects the degree of abrasion.

 

A typical stonewashing process begins with desizing, followed by stone abrasion, rinsing, top brightening, and softening, You can find out more about a typical stonewash cycle in the technical tips segment of this CD. While some stonewashing is still done in belly washers, rotary machines are becoming the machine of choice. The advantages of rotary machines include larger diameter drums, microprocessor control, and ease of unloading. No matter which type of machine is used thought, it will eventually need to be replaced. Not only is stonewashing hard on the machine’s drum but the stone sludge and small stone particles of its effluent clog waste piping and trenching.

 

Once the stonewashing cycle is complete, the jeans and stones are removed from the machine. Some stones and stone residue remain on the jeans, because the residue is abrasive it will damage any washer or dryer that the jeans will be loaded into next, so it must be removed either by hand or by machine. Hand-removing stone residue is slow, costly, and labor-intensive. Workers must manually shake the stone residue off the jeans and remove any small stones or particles inside the jeans or in the pockets. It’s virtually impossible to remove all the particles from the pockets which leads to an interesting phenomenon. Consumers often take the remaining residue as a sign of authentic stonewashing. In addition to manual processes, stones and residue can be removed by a destoning machine which is quite efficient and involves very little labor.

 

After stonewashing the jeans and stones are unloaded into a truck. The truck is moved to the back of the destoning machine and the content is placed inside. The de-stoner consists of a revolving cylinder with spiral veins or baffles inside. As the cylinder turns, the residue is spun out of the garment and through the baffles. The stones drop out of the bottom of the machine into a bin, while the jeans are spiraled through the cylinder and out the back of the machine.

 

 

Enzyme Washing

 

Enzyme washing is a wet processing washing technique that softens the feel of the fabric and brings out highlights. In the jeanswear industry, enzymes are used as an alternative or addition to stonewashing. Enzymes are organic substances, specialized proteins found in all living organisms that serve as natural catalysts for biochemical reactions. They are safe and easy to use and attack and degrade specific substrates under mild conditions. Since they work under mild processing conditions, they cause less damage to denim fabric during processing, or to generate more wear and to give the feel of a full stonewash, enzymes can be combined with pumice stones.

 

Many different enzymes are used in denim wet processing, each with a specific purpose. The two most often used are alpha-amylase for desizing starch and cellulase for abrasion and biopolishing. The cellulase enzyme biopolishes cotton by hydrolyzing the fiber surface. Unfortunately, this process results in a loss of fiber from the surface of the fabric.

 

Recently, laccase enzymes have been engineered to decolorize the indigo dyestuffs on the yarns without causing fiber loss. Enzymes offer results similar to those achieved by stonewashing but with several advantages. For example, they are environmentally friendly and require less labor. Jeans washed with enzymes are softer because the enzymes digest the fabric, breaking down the surface fibers. As the surface fiber is removed, so too is the surface color leaving an ultra-clean surface. This gives the jeans a smoother, cleaner appearance even after multiple home launderings.

 

The major advantages of enzyme treatments over stonewashing are that larger washer loads can be used, no stone handling is required, no de-stoning is required, there is no stone residue, machine wear is reduced which means longer machine life, labor is greatly reduced, and plant noise is greatly diminished. But although enzymes have advantages over stonewashing, they also have some disadvantages. One is that they are moderately expensive, another is that they can cause weight reduction and sometimes strength loss in fibers.

 

Enzyme applications are any other chemical application technology in that they require certain parameters in order to do their work. The variables that need to be considered include the type of enzyme, the pH of the solution, the temperature of the bath, the time the garments are processed in the bath, enzyme dosage, the liquor ratio, the mechanical action of the machine, any needed auxiliary chemicals and the type of fabric. pH and temperature are perhaps the most important. Many enzymes simply won’t work if pH and temperature limits are exceeded. This is particularly true of cellulase enzyme processing. Mechanical agitation is another key component in enzyme washing since the enzymes themselves only partially remove hydrolyzed cellulosic material mechanical, agitation must do the rest. Agitation also reduces processing time and improves fabric preparation.

 

As a comparison, let’s take a look at both enzyme-washed and stonewashed denim jeans. With both the stonewashed and enzyme washed, the overall color is similar and the differential washdown around the pockets is also similar. Two types of enzymes are used on denim, neutral enzymes, and acid cellulases; both are effective on cotton denim but result in a slightly different effect as you can see. The type of enzyme used depends on the process being used and the desired effects of that process. For example, a common process is a dark wash using acid-stable enzymes. Its typical processing sequence is desizing, followed by abrasion using acid-stable cellulase with maximum color retention, top brightening, and finally, softening.

 

Another common enzyme process is the enzyme wash with maximum abrasion. Its processing sequence includes desizing, abrasion using high levels of acid-stable or neutral cellulase enzymes, top brightening, and softening. Yet another process is used for a typical dark wash enzyme procedure that softens fabric while maintaining a dark indigo shade. It includes desizing, followed by abrasion using neutral cellulase with maximum color retention, followed by top brightening and ending with softening. Using the right type of enzyme is critical to maintaining proper pH, which in turn is critical for successful enzyme washing. It’s particularly important to prevent backstaining.

 

 

Backstaining

 

Backstaining occurs when indigo dye removed from the white filling yarns is redeposited on the yarns during processing. Backstaining is less likely to happen during enzyme treatment if a pH greater than 6 is maintained. So neutral enzymes, therefore, allow less backstaining than acid cellulases. But acid cellulases result in greater abrasion so, depending on the desired effect, buffering agents may be used to reduce backstaining in such low pH situations. Backstaining can also be minimized through the use of special dechemicals that prevent the dyes from being redeposited. However, it is important to use the correct specialty chemical, one that won’t adversely affect the cellulase enzyme. Other ways to prevent backstaining include not overloading the machine, using shorter cycles after bleaching, and running extra rinse cycles. A fixing agent can also be used to lock in color. As mentioned earlier, pumice stones can be used with either acid or neutral enzymes. Many washes use porous ceramic or plastic balls called dingers instead of stones. These come in many different sizes and shapes from golf balls to large rubber balls.

 

The generic procedure for a heavy wash using stones and enzymes is as follows: desizing, then abrasion with a cellulase enzyme in a one-to-one pumice stone to fabric ratio, top brightening, and finally, softening.

 

 

Diatomaceous Earth (Di-Earth)

 

Another way to achieve a novel look for denim is through the use of a naturally occurring material known as diatomaceous earth or di-earth. Di-earth consists of fine fossilized remains of ancient animals. During denim fabric processing, the di-earth abrades the surface of the fabric. In the waste treatment effluent, it readily sinks and is easy to filter. However, di-earth can solidify in drains if it is not completely flushed from the waste system. Di-earth can be used with or without enzymes. The final wash down effect depends on the amount of di-earth used and the length of the abrasion cycle.

 

 

Perlite

 

Another abrasive material used in denim garment finishing is perlite. Perlite is similar to pumice stone and is about 1.5 millimeters in diameter. It produces a softer, more pliable finish than stones or di-earth and also reduces the wear on garment machines. Because perlite is small, it can generate a worn look through the entire fabric and not just on the outer surfaces. Perlite is a processed natural deposit with good abrasive properties. Unlike di-earth, it floats so care must be taken not to use too much. It must also be skimmed during waste treatment and thoroughly flushed from the machines and drains after processing so it does not clog the drains. Some of the names perlite is sold under include Beadwash, Oceanwash, and Pearlwash.

 


 

Color Discharge

Discharge washing is a chemical washing technique that removes color from selected areas of dyed fabric. The chemistries used for discharge washing are either strong oxidizers, like potassium permanganate, or reducing agents, like sodium hypochlorite. Ozone processes, which are new to the industry, may offer a clean and simple method for color discharge.

 

Some popular effects achieved by wet discharge include acid wash, moon wash, fog wash, marble wash, ice frosted, snow wash, electric wash, and galactic wash.

Both chemical and physical systems can be used to discharge color and it can be used as a single, stand-alone process or in various combinations to achieve unique effects. These effects can be placed all over the garment or localized in selected areas. They can be very subtle, slightly less subtle, or remove dyestuff completely from the fabric for the most dramatic effect. Because of its chemical nature, indigo dye is easily discharged. Effects are simple to achieve because the dyestuff is only on the surface of the fiber and yarns making it easy to remove.

 

 

Potassium Permanganate

 

Potassium permanganate is an extremely effective discharge. When it is applied to fabric, the fabric turns a purple-ish brown so you can tell exactly where the chemistry has been applied and when processing is complete, it leaves treated areas completely white. Potassium permanganate is available in liquid, powder, or pellet form. Typically, it’s applied to dry fabric however in some processes, the garment is wet but fully extracted before the chemistry is applied. Treating fabric when it’s dry will result in a whiter discharge. Potassium permanganate can be applied by brushing or spraying both of which create a large or distinct area of discharge. For example, it can be applied to the thighs and seat of the pants to give an aged effect.

 

 

Brushing

 

With brushing, some type of form or mannequin is needed to hold the garment. Jeans, jackets, and other denim items can easily be treated in this manner. Brushing requires some skill to be effective. First, a paintbrush is dipped into a potassium permanganate solution in a paint tray. The excess is brushed onto a fabric blotting-pad to remove any excess liquid. Then the solution is brushed onto the denim surface where the discharge is desired. If the potassium permanganate saturates the jeans or is improperly applied overly white spots or blotchiness can occur. A significant amount of brushing is needed to cover the desired area, so hand brushing is often used to treat very specific areas.

 

 

Spraying

 

For large areas, the preferred treatment method is spraying. As with hand brushing, considerable experience and skill are needed for effective spraying. The garment is usually placed in a booth designed for spray finishing. The garment hangs on a mannequin while the operator sprays it. Water cascades down the back of the booth behind the garment to capture any spray not directed onto the garment. For novel effects, potassium permanganate can be applied to dry fabric that is tied or restricted so that only certain portions of it are exposed to the chemistry. The process is like tie-dyeing.

 

 

Garment Washing Machine Treatments

 

Brushing and spraying are just two application techniques for wet discharge. Another option is to treat the garment in a garment washing machine. This produces an all-over effect in the fabric.

 

Acid-Washed

A good example of this type of treatment is the acid-washed effect. “Acid-washed” is a misnomer for this well-known process because it uses no acid. Typically, the discharging agent is either sodium hypochlorite or potassium permanganate. A basic acid wash procedure includes preparing the garments, preparing the machine, performing the discharge procedure, running the reduction bath for neutralization, top brightening, softening, and tumble-drying. To prepare jeans for acid washing, they are usually first desized in a separate machine. It is also important to run them through an abrasion cycle such as an enzyme treatment to give some variation to the surface of the fabric. If no abrasion is performed prior to acid washing, the resulting effect will look flat. Finally, the jeans must be uniformly extracted to the lowest possible moisture level. Once they have been extracted, they are moved to a separate acid washing machine.

 

To prepare the garment machine for acid washing, it first must be drained so that no water is left in the drum. Then the drum holes are covered with a plastic liner. The liner keeps the potassium permanganate-soaked stones used in the process from falling through the holes in the drum. Typically, pumice stones are used weighed at a ratio of 2:1 to dried garment weight, then the stones are soaked for two hours in enough potassium permanganate solution to just cover the top of the stones. The concentration of the potassium permanganate solution can be altered depending on how much discharge is desired. Sodium hypochlorite can also be used instead of potassium permanganate.

 

Once the stones have been soaked and drained sufficiently, they are placed into the dry machine and tumbled for 5 minutes with white dummy fabric. This removes any excess solution from the stones. The dummy fabric is then removed and replaced with the garments to be processed. The garments are tumbled at high speed, with reversal, for approximately 15 minutes. Both speed and time may need to be adjusted slightly depending on the machine. Once the process is complete, the garments are removed immediately to avoid creating hot spots or areas of complete color discharge in the fabric. The stones are separated from the garments with care taken to ensure that all the stones are removed. The garments are then moved to a separate machine where they are rinsed and neutralized. Finally, they are softened as desired and tumble-dried. Another common washing garment process is called electric wash.

 

Electric Wash

Electric wash involves the use of potassium permanganate powder and dingers. The process includes preparing the garments, preparing the machines, running the discharge procedure, running the reduction bath or neutralization, top brightening, softening, and tumble-drying. As with acid washing, electric wash garments are first prepared and extracted in another machine. Before they are transferred to the garment washing machine, the machine must first be drained so that no water is left in the drum. The holes of the drum are covered with a plastic liner to keep the potassium permanganate powder from falling through the holes in the drum. The weight of the potassium permanganate should be 45 – 50% of the weight of the garments. The powder is available in strengths from 1% to 4%. Once the powder is weighed, it is placed inside the drum on top of the plastic liner. Next, dingers are weighed at a ratio of 2.5:1 of dry garments and placed on top of the powder. The next step is to place pre-wet garments on top of the dingers. It’s important that the garments touch only the dingers and not the potassium permanganate.

 

Next, the contents of the machine are tumbled with reversal at 30-35 RPM for 15-20 minutes. As with acid washing, both time and speed may need to be adjusted slightly depending on the machine. Once processed, the garments are removed immediately to avoid creating hot spots in the fabric. The dingers are separated from the garments and the garments are placed in another machine, rinsed, and neutralized with a reduction bath. Then they are softened and tumble-dried.

 

An alternative to using potassium permanganate powder and dingers is to use potassium permanganate pellets. The process is the same for both, though the pellets are weighed at a 2:1 ratio to the dry weight of the garments. Potassium permanganate pellets can also be made at different strengths.

 

 

Bleaching

 

Bleaching chemistry is like discharge washing in that color is reduced or removed but not necessarily completely. Sodium hypochlorite, which is often used for discharge washing, is also used for bleaching but in a different concentration with a different delivery method and for a different effect. Bleaching alone cannot create localized areas of effect. Localized areas of effect can only occur if the area is first sanded, discharged, or prepared by another method. As with acid washing, bleaching requires an abrasion cycle prior to processing to give some variation to the surface of the fabric, if not the fabric will look flat.

 

All bleaching uses the same procedures, the only difference is the amount of chemistry used. As you can see, different amounts result in different intensities. A typical bleach down process includes desizing, abrasion using cellulase enzymes, stones (or both), bleaching, neutralization, top brightening, and softening. In bleaching with sodium hypochlorite, the neutralization step is called an anti-chlor.

 

Hydrogen peroxide is the most used chemistry for the anti-chlor process. Laccase enzyme is used in denim finishing to break down color to achieve an effect like that achieved by bleaching. The most important difference between the two methods is that laccase enzymes don’t require anti-chlor neutralization. This cuts down on the use of water, chemicals, and time. Laccase treatments do require a desizing step with an amylase enzyme and an abrasion cycle prior to the laccase step. The abrasion cycle could use cellulase enzyme, pumice stones, or both. A typical laccase enzyme procedure includes: desizing and abrading the garments, treating them with laccase enzyme, repeating the laccase enzyme step as needed to remove more color, rinsing, softening, and tumble-drying.

 

 

Ozone Treatments

 

Ozone gas is a natural part of the earth’s atmosphere but when ozone is produced by industry or automobile exhaust, it causes air pollution issues. Ozone pollution can cause dyes to oxidize, destroying or changing the color of textiles. This is a particularly troublesome issue in garment shipment and storage. Indigo and sulfur dyes are prone to ozone fading, particularly if back staining has occurred. With regards to indigo-dyed jeans, color discharge is often a desirable effect in denim garments so it stands to reason that controlled ozone treatments could be used to achieve that effect since ozone is such a powerful oxidizer and bleaching agent.

 

In ozone treatments, the gas is generated as needed and injected into a closed machine. The ozone is used as it is generated. It creates a soft hand and has a washed down appearance like pigment overdyeing. Like other chemical treatments for color reduction, the effects of the ozone process are dependent on time and chemical concentrations and, as with other chemical processes, some form of garment abrasion must be included to give character to the fabric. If proven to be commercially effective, ozone treatment has several benefits over other chemical processes. They include reduced water usage, reduced chemical usage, shorter processing time, effective results on most dyestuffs, and the elimination of fabric degradation. Ozone used in garment washing can be environmentally friendly. In some circumstances, water used during the ozone process can be recycled and reused. Currently, ozone treatments are in the developmental stage.

 

 

Top Brightening

 

After any garment’s wet finishing process, the fabric can be brightened for a cleaner appearance. Top brightening uses sodium perborate in an alkaline bath to create an oxidated scour. The process adds more contrast between the white and light-colored areas and the darker areas of the garment. Top brightening is a simple procedure and is usually applied just before softener application. A typical procedure uses an alkaline detergent and an optical brightener at around 180 degrees Fahrenheit for 15 minutes.

 


 

Chemical Finishing

Chemical finishing includes processes like softening, resin finishing, tinting, and overdyeing. Some of these processes require only tumble drying, while others require a curing step.

 

 

Softeners

 

Softeners refer to a wide variety of chemicals, for denim garment applications they must be able to be applied in a rotary machine.

Cationic softeners are a good choice because they produce a fluffy, silky hand on most fabrics. It doesn’t take much to get this effect on cotton because cationic softeners have a positive ionic charge and wet cotton has a negative charge. This gives cotton a high affinity for cationic softeners. Another advantage of cationic softeners is that they easily exhaust and are compatible with most resin finishes. In addition to cationic softeners, non-ionic softeners like polyethylene and many silicones can also be used.

 

 

Resin Finishing

 

Resin is the name commonly applied to chemical compounds that react with cotton or other forms of cellulose. These compounds modify cotton’s performance by improving shape retention, decreasing shrinkage, and improving colorfastness. On denim, the resin is applied for improved color retention, faster development of abraded areas, and helping in the formation of whiskers, pleats, and creases.

 

The process for resin finishing of denim garments includes applying the resin formulation to the garments, extracting the resin (if needed), tumble drying at a low temperature, pressing (if needed), dry finishing, and oven curing.

 

Resin finishing is a form of crosslinking in which chemical bonds are created between polymer molecules to form a three-dimensional polymeric network. In addition to the actual resin, resin finishing formulations contain a wetting agent and a catalyst. The catalyst activates the resin and causes the chemical crosslinking to occur. The process is known as curing. For the chemical reaction to be completed, the resin finish must be cured at a high temperature, approximately 300-320 degrees Fahrenheit. This is done in a curing oven—either a semi-continuous batch oven or a continuous oven. A batch oven consists of a reaction chamber in which garments are hung for curing. In some cases, the garments are placed on special hangers and put in the oven one by one. More commonly, an entire rack of garments is rolled into the oven. With a continuous curing oven, garments are placed onto an overhead rail system which moves the garments through the oven. The system’s speed is set for the proper curing time for each product.

 

When curing takes place after garments have been pressed and dry finished, it’s called a post-cure system. Denim jeans can be post-cured in either one of two methods: immersion or metered addition.

 

Immersion Method

In the immersion or “dip” process, garments are placed in a garment washer in a bath of the finishing formulation. Once the garments are saturated, excess solution is drained into a storage tank where it is saved for further use. The garments are then centrifugally extracted and tumble-dried at a low temperature in a drier allocated for resonated goods only. If the garments are wrinkled after drying, they are either steamed or hot head-pressed. Then, any desired dry garment finishing effects such as whiskering or pleating are added. Finally, the garments are cured in an oven.

 

Metered Addition Method

Metered addition is a precisely controlled method for infusing denim garments with a resin formulation as the garments tumble in the garment washing machine. Either dry or wet garments can be finished by metered addition. The process begins when those garments are loaded into an empty rotary machine with a specially designed door with multiple spray heads. A microprocessor turns the spray heads on and off as needed allowing for complete and uniform application of the chemistry to the garment. As the garments begin tumbling, the heads spray a resin bath onto them in precisely the amount needed for a uniform application. There is no waste or bath to pump into a holding tank. Once the garments have tumbled for the correct amount of time for equal abrasion of the chemistry, they are removed from the machine and tumble-dried at a low temperature in a dryer allocated for resinated goods only. When the garments are dry, they may be steam-pressed or if very wrinkled, hot head-pressed. Any desired dry garment finishing effects, such as whiskering or pleating, are added. Finally, the garments are cured in an oven. Metered addition effectively has no chemical waste and uses less water and energy, so it is a more environmentally friendly process. Some of its other benefits include a lower exposure to formaldehyde, the creation of a softer hand than fabric finishing, and decreased shrinkage and better fit.

 

 

Tinting & Overdyeing

 

After processes like discharge and heavy sanding, many denim garments are overdyed. The tint or overdye shows up on those areas of the garment where the discharge or sanding process has removed the indigo color. A common tint is a dirty-looking brown. Some garments have very little indigo dye loss before they are overdyed. In these garments, the white or undyed filling yarns are overdyed. These overdyed shades range from light pastel to dark black. To overdye accented areas, a direct dye is used during one of the final steps in the rotary machine processing. A common overdye bath contains water, a wetting agent, and the dyestuff. The garment is processed for the correct time, temperature, and chemistry. Once the garment is dyed, a softener and color fixing agent are applied. The fixing agent locks in the dye to the fiber, without a fixing agent the dye won’t adhere well to the garment fibers. Once the color is fixed, the garment is finally dried.

 

 

TERMS TO KNOW (click to flip)

Desizing

Preparation wet process that degrades and removes the size from the warp yarns of a woven fabric thus enabling the…

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Stone Washed

Garment wet process that imparts a worn, washed out look. Can be done mechanically (pumice stone or dingers) or chemically…

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Acid Washed

See Stone Washed.

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Brushing

Finishing process performed on a fabric that raises up fibers to create a specific feel (hand) or look. Not the…

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Spray Finishing

The application of a chemical finish by spraying the product to one or both sides of the fabric.

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Bleaching

Preparation wet process that is done to a greige substrate in order to impart a white base for dyeing light…

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Resin Finishing

Chemical used to impart durable press properties in a fabric or garment.

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Curing

The process by which resins are set into a fabric or garment at elevated temperatures.

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Loop Drying/Curing Oven

A low tension fabric dryer that hangs the fabric in vertical loops over continuously moving bars through a heated oven….

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Garment Dip Finishing (Immersion)

A garment finishing system that applies the chemistry to the garment in either a garment machine or a vat. The…

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Metered Addition

Spraying process for the precise application of a solution (dye, finish, bleach, etc.) onto garments while tumbling in an enclosed…

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Over Dye

To dye a fabric containing previously colored yarns or, in some cases, uncolored yarns to get a cross-dyed effect. Also…

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