Author: Sandeep Agarwal

 

Acid wash is again becoming popular on denim jeans and we are going to see more of acid washes in the coming seasons. Here , lets have a quick look at the acid washing process .

An acid wash finish treatment creates significant contrasts in the color of the denim material. It can be done on Indigo & Sulphur base fabric garments. As the randomly faded, acid washed style came into vogue in 1980s, the process of treating denim in such a way began to become increasingly refined. Some tried to use a method similar to the stonewashing, yet the fading did not occur as dramatically or throughout the material.

In 1980’s this washed being launched as first innovative finish on denim ever. This was being done by soaking stones in Bleach and making acid wash effect followed by neutralization. But this process was not so re find to get some how consistent & smooth effect on denim. In early 2000 some laundry tried doing the same wash soaking thermocol bolls in bleach or pp solution to get this desired effect.

While this process can be done using either light bleach, chlorine , potassium permanganate etc. The most popular is PP Bleach and will produce the best acid washed results. Doing the process is very simple , but following all parameters in correct way to have right & repeatable results. The load size of garments, machine drum diameter, quantity of soaked stone / towels & skilled operator.

Initially, the Acid Wash process involved soaking pumice in Industrial Strength Chlorine .However, it was discovered that potassium permanganate was more controllable and just as strong an oxidizer. They simply marinated pumice stone in it and then vacuum packed the stone to the required moisture level. Acid wash was a chemical process on  denim that stripped the top layer of color off to a white surface with the undertones of navy blue remaining in the jeans.

The Materials

The process of acid washing jeans involves porous pumice stones or small towel pieces and chlorine or Pp Bleach, such as you would put into a bucket or in drum for soaking process. Sodium-bisulfate is used in the second washing for Neutralization. Also recommended is access to two separate washing machines. One for Acid Washing & another one for further process i.e. Neutralization etc.

The Acid Washing Process On Denim Jeans

The process of acid washing jeans used chemicals, stripping off the color of the top layer, leaving the white fabric exposed. The color remained in the lower layers of the material, giving it a faded look. Acid washing could be done overall or made to look splotchy.

1.Soak porous pumice rocks or pieces of towels in chlorine or PP bleach solution for about 20 minutes to an hour. The longer you soak the pumice or towel, the more prominent the effects will be.

2.Once the stones are saturated with chlorine/pp, remove excess water from stones/towel then put the stones in machine followed by the jeans in a washing machine for about 20 minutes. Make sure machine do not have single drop of water, open the drain during complete process

3.At this time, check on the jeans to ensure they look acceptable, and then move them to another washing machine for a regular washing process. Too long in the first machine can totally bleach or ruin the jeans, and too little time may not produce the desired results or can make patchy appearance. Check on the jeans once every 10 minutes or so during the second wash process of neutralisation to ensure the desired look is achieved.

4.Next, fully dry the jeans in a dryer that gets nice and hot.

Precautions

Any time we mess with chemicals such as bleach or chlorine or PP, be sure to protect workers by wearing mask & aprons , so it is best to be fully prepared. Also, protective rubber gloves and safety glasses are highly recommended. These products can burn skin and eyes pretty badly.

About Author : 3E’s Consultants, Group of experts, focused on Denim Fashion, Providing consultancy to all Denim Garments Finishers..Contact for further info email here

The distressed jeans that we see around everywhere undergo a wide variety of wet as well as dry treatments to get the desired effects.  Here I shall try to explain some basic Denim Dry Processing techniques. In the creation of vintage denim jeans, dry processes play a very important role and hence important to understand.

Denim Dry Processing – Basic know how

Destroying denims is as much an art as it is a technique. Details are added using a fine abrasive paper on a scraping tool. And extra whiskering can be added with sand paper. Sometimes a bit of local tint staining is being done into the local areas to emphasize the lighter parts. The jeans then go for a washing with pumice stone to blend in the whiskering and tinting / over dyeing. Where the folds and wrinkles go is where the art part comes in, it’s often through observation of where wear patterns are typically found. For some of mine I have several pairs of old well worn thrift store jeans that I use as a template to guide where I want the wear patterns. I chalk in where I want the details and then they are finished off site by me in my finish workshop. Some of what is done to customize jeans are patented secrets, no one other than those who work for these companies knows the exact techniques or the abrasives and chemicals used to achieve certain special effects. Here I am revealing some basic facts to the denimsandjeans.com readers……………..

Below is list of operations being carried out on denim garment to achieve VINTAGE (used/worn out) look……

• Hand Sand / Hand Scraping
• Sand blasting
• Whiskers
• Chevrons
• Knee Star / knee whiskers
• Hot Spot
• Tacking
• Grinding
• Damages / Destruction
• PP Spray
• PP Brush / towel
• Patch / repair
• Bleach spots
• Resin application
• Pigments & Local tint application etc…..

1.Denim Hand Sand / Scraping

Hand sand is step which is generally being done in rigid form of garments to get distress look. Locations can be front thigh & back seat or its can be overall / global application as per Standard. Emery paper is being used to scrape the garments in particular placement & design. Emery paper comes in different number generally start from 40 till 600 and above , higher the number finer the emery paper, lower the coarseness of the paper. In garment industry from 220 , 320 & 400 number papers are most popular & widely used.

Purpose of doing this process is make used worn out look to the garments.

The most important factor is to select right number of paper according to the fabric strength & intensity need. Feathering / merging white sanded part to dark blue area in such way that it should look natural & not artificial.

Scraping can be done on inflated rubber balloons for better effect ( horizontal or vertical its up to operators convenience ) , even it can done plain wooden board of garment size & hand pressure should be uniform in order to get better results.

Hand sanding must be started from intense part & feathering out on less intense part gradually. One garment must by done by one operator only to have balance intensity on both the legs.

2.Sand Blasting

This process is isolated now a days due to health hazards & buyers do not like the results of sandblast because its covers the characteristics of fabric. This process being done by using different kin d of sand blown to garments with air pressure to rub out the color.

3.Whiskers/ Moustaches , Chevron , Knee Star, Hot Spot

On Denim, whiskers / Mustaches , Chevrons are nothing but the worn out lines / impression generated by natural wearing on hip & thigh area. There are many designs & pattern available.

This is being done manually with help of sharp edge Emery paper rolled on fine wood stick or pasted on plastic material. Before starting execution placements & pattern must be marked on garments, this will help operator to execute the pattern right to match the aesthetics of garment.

Hot spots are heavy/intense area on thigh or knee which is made purposely to create used look & on knee area if any whiskers line are there, called knee star.

All above operations are carried out in width direction hence its appears intense than hand sand with less strokes, because hand sand is carried out in length direction.

4.Tacking & Grinding

Tacking: is a process which is being done by swift tag machine with the help of plastic or nylon tag pins in rigid form of garment to get very heavy contrast ( rigid & washed ) on waistband, bottom hems, back pocket & front pocket corners etc.. after completing wash cycle, it must be removed from garment before making softening.

Grinding: is being done on pocket edges & bottom hems edges by running against abrasion surface or stone to achieve worn out effect. Many different make of machines & pen grinding tools are available in the market which runs with pneumatic system.

5.Damages/Destruction

One of the most popular distressing effects currently , ‘Destruction’ is an art which make denim look unique & used. To make destruction pen type of stone tools being used in mid of wash process to apply on desired area. It can also be achieved by cutting it thru knife the warp yarns & keep the weft yarn as is to show white thread. Holes also can be made by cutting weft & warp yarns. These are all manual processes & every garment will look unique & different than others.

6.POTASSIUM PERMANGNATE SPRAY/RUB & BLEACH SPRAY

PP Spray is being done  on denim garments to achieve local abraded area to appear whiter than back ground indigo color shade. This can be applied by spray gun or by towel dipped in to PP Solution & rubbed on desired area followed by neutralization in wet process. This process can be done in rigid after doing hand scrape or in the middle of the wash. Doing after enzyme or bleach cycle will give more natural & white effect that doing in rigid. There are many additives can be added in order to achieve desired intensity and look.

The same way bleach solution also can be spray or rubbed on the garments on desired area. But this process is very complicated & needs highly skilled operators to execute it followed by immediate neutralization.

There are many parameters needs to be taken into control for doing PP or Bleach spray…. Spray gun pressure, width of spray, flow & way of spraying.

Note:Safety of operators must be taken in to consideration and it must be ensured that he should wear mask, gloves & eye glasses etc…

7.Patch & Repairs along with Bleach Spots

These are totally manual processes to give uniqueness to Denim and to make it  look VINTAGE.

First cut or damage the units intestinally to desired area & then make hand repairs or machine repair to look natural. Diluted bleach can be used to spot the desired area followed by neutralization in wet process.

These process are time consuming hence productivity is low & reproducibility is very difficult but similar aesthetics can be achieved.

When we talk about Vintage denim, every garment should look unique & not a photocopy !. These garments are sold at very high prices so customer should have a feeling of uniqueness & feeling different from others. Vintage denim are signature/ autograph of a brand & its image.

8.Resin Application( 3D Effect )

Resin ( Formaldehyde free ) being used for achieving 3D effect ( 3 Dimensional ), Rigid Look etc. This process can be done by spraying or dipping the garments in to Resin, Catalyst, Silicone & PU solution in right combination according to the fabric strength & desired effect needed.
After application of resin solution in right proportion, make manual designing as needed on the thigh, hip & back knee area to get 3Dimentional effect. After making it , it should be manually dried with hot press or hair dryer & then must be cured in oven at right temperature, time as mentioned in resin product manual.

If resin not cured properly , 3 D effect will not be permanent & can cause skin irritation/rashes to the wearer. Highly skilled operators needs to execute this process in order to get consistency & uniformity.

Whole garment can have crushed look by resin dip & crushed manually followed by oven curing. Silicone plays an important role in getting softer hand after oven.

Special streaky effect & Crackles also being done by applying resin on desired area followed by scraping & pp spray then neutralization.

9.Pigments & Local  Tint ( Staining)  Application

Need to choose right color of pigment or tint with binder or fixer to apply locally on denim to get vintage look. This process also needs an artist to execute it nicely to merge the tint with ground indigo color & should not look too artificial. Pigments & Local tint also can be applied through spray gun or rubbing on desired area of denim garment. After application its must be cured in order to have permanent effect on jean.

As we can see from all the dry denim processes mentioned above, they are mainly manual processes. The quality of the worker can make or break the garment. Hence , great care has to be given to select the right personnel for these jobs.

About the Author : This is Guest article by Saurabh Rai .He is a  Textile Chemist by Profession & a Denim Finishing Expert .He is working in one of the most well known denim brand in Middle East as their denim washing head. Contact him on email here  . Want to write guest articles ? Check here

Fashion is today incomplete without denim. Denim comes in all forms, looks and washes to match with every dress . It would be difficult to believe that the same denim was originally employed in clothing for the pants and overalls worn by miners on the west coast(US). A number of technological factors have contributed to making denim the fashion icon that it is today – including vast improvements in spinning, weaving, finishing etc. One of the most important part of creation of the beautiful denim jeans is the washing . Washing plays such an important part in the denim chain because of the umpteen effects that the consumers are looking for on their jeans . Lets talk a bit about denim washing …

 

BASIC DENIM WASHING PRINCIPLES

Below is the brief introduction to common steps done & followed in denim garments washing in Laundries across the world. Different kind & make of machines being used across the globe to hit similar results.

Every small step in denim washing makes a big difference because indigo dye has very poor wet & dry rubbing fastness. All parameters are critical to maintain for repetitive results. Eg Many laundries across the Globe ignore the importance of pH M:L:R & R P M of machine.

Some  important steps in the process of Denim Washing

 

1. Pre treatment ( Desizing, Rinsing, Scouring etc)
2. Enzyme or Stone wash
3. Clean up to adjust the desire effect
4. Bleaching
5. Tinting / Dyeing
6. Softening & Much more…..

1.PRE TREATEMENT

This is very first & basic step but most important step of washing. Here the fate of denim garment is decided that its going to appear good or bad. Good Pre treatments avoid streaking, stiffness & color loss. This process removes impurities, starch & stains during handling of fabric.

This step is also called desizing ( Removal of Size applied during denim fabric making in weft yarn ). All the woven fabric contains size on them due to reasons to strengthen the yarn for weaving.There are many types of sizes available in the market but they can be divided in two major groups.

1. Water Soluble (CMC or PVA based sizes ) and
2. Dissolvable sizes in water ( Starch based ). Starch based sizes are most commonly used due to cheap prices & readily availability.
   

Methods of Removing Sizes from Denim Jeans……

· Washing with High Alkaline agents ( i.e. Soda ash )

· Washing with High Acidic agents (i.e. Acetic acid )

· Washing with Oxidative chemicals ( i.e. Hydrogen Peroxide )

· Enzymatic desizing with Alfa amylase .. This is eco friendly & convenient .

2.Enzyme  & Stone Washing  Process  Of Denim  Garments

There are four kind of Enzymes available in market for Denim Laundry business..

• Amylase …. Desizing
• Cellulase …. For Salt & pepper effect , contrast
• Laccase…. … bio bleaching
• Catalase …… Peroxide killer

Enzyme is kind of protein that is obtained from fermentations method from naturally existing bacteria & fungi. The structure of Enzyme is a biological polymer and it can be found in every cell. Generally called as Cellulase & it works on cotton( Cellulosic fiber ) only. Enzyme are living organisms which will attack a specific molecular group.

There are mainly three kind of Cellulase being used for Denim washing , Neutral, Acid and Bio polishing Enzyme. Enzyme are very sensitive with parameters in washing cycle i.e, pH , Temperature & time. If any of these parameters are not up to the mark, result will not be accurate.

The reaction of enzyme can be easily controlled, its biodegradable products, so they eco friendly.

Bio Polishing Cellulase are being used to have protruded fiber removal from denim & oven fabric. This is also widely known as Anti pilling enzyme.

Any Cellulase used in process must be cleaned/killed after the process completion by simply disturbing the parameters ie. By raising high temp. or raising pH to alkaline where no Cellulase withstand.

Cellulase are available in 3 categories

 Neutral

Acidic &

Hybrid enzymes.

Neutral enzyme gives better salt & pepper effect with very less back staining & its generally come sin powder form & also retains better strength of fabric than acidic Cellulase. Where as acidic cellulase give faster results but with too heavy back staining & cuts down the indigo color, also affects the strength of fabrics.

Now a days laundry people needs faster results in less time & money hence chemical suppliers combined Neutral & acid cellulase in such way that it works faster & with better results than acid cellulase with cost effectiveness & known as Hybrid enzyme.

Laccase is bio bleaching agent & alternative for conventional bleaching agents. This impart greyer cast to blue denim & enhances salt & pepper effect. But due to high cost & low self life, laundries do not prefer it.

3.CLEAN UP

After finishing Enzyme wash it is must to add clean up process for better results & garments appearance & that can be done in various ways & methods. As clean up is a must process to be carried out after every chemicals steps done for any garments which allows next process to happen smoothly. All processes mentioned below kill/ deactivate the active enzymes process which is necessary in order to protect/retain garment strength……

• a.Hydrogen peroxide in alkaline pH clean up enhances the brightness & rich blue tone of indigo.
• b.By using non ionic detergents in medium to high temperature
• c.By doing two good hot water rinse etc….

 

4.BLEACHING

  

This in one an important step in washing denim & can be done by various bleaching agents …..

• a.Calcium hypo chlorite
• b.Sodium hypo chlorite
• c.Hydrogen peroxide
• d.Potassium permanganate

First two chemicals are commonly being used for every medium to vintage denim but when it comes to super vintage & light shade its advisable to use potassium permanganate bleach to cut the color faster till half way & then neutralize it & go with Liquid ( Hypo ) bleach to adjust the desired shade. This process helps to get Greyer cast & also protects the lycra/spandex , retain elasticity.

Hydrogen Peroxide is rarely used as bleaching agent when very less color loss required or if fabric is sulphur top. As it takes longer time to give desired effect.

Potassium Permanganate is also being used on 100%  sulphur black denim fabric for bleaching/reducing agent to get unique effects. As its not production friendly till laundry have very expertise team to handle this program, otherwise it will result in many shades & cast.

Proper Neutralizations of bleaching process is very essential in order to get rid of fabric strength , bad smell from garment, yellowing & skin irritation etc…

4.Tinting & Dyeing

 

Tinting is a process where very less amount of tint is involved & mainly direct dye is being used to do this process. This is being done to change hue/cast/tone of indigo. As soon as quantity of tint color increases & it cover up indigo, reaches the level of dyeing.

Tinting being used to give garments a used / vintage & muddy look. This process takes from 5 minutes to 15 minutes time for better results followed by dye fixing & clean up of superficial dye.

Dyeing is being done on very light shade of Indigo, Ecru/ grey denim & Ready for dyeing denim.

•  There are various Types Of Dye . THe comparison of these dyes is given in the chart herebelow:

1-Direct Dyes

2-Reactive Dyes

3-Pigment Dyes

4-Sulphur Dyes

Direct Dyes	Reactive Dyes	Pigment Dyes	Sulphur Dyes
Economical	Costly	Cost Efficient	Economical
Wide range of shades	Wide range of shades	Styling ( limited to dull shades)	Shades are dull
Short Cycles	Long Cycle	Short to long Cycle	Short to long Cycle, depends upon shade
Ease of application	Water Consumption High	Machine contamination, but hard to obtain consistency, harsh hand feel	Sulphur Odour & harsh hand feel
Smooth Appearance	Smooth Appearance	Smooth Appearance	Smooth Appearance

 

5.SOFTENING PROCESS

Softening process of Denim is very critical. As denim is very heavy in compare with other fabrics hence its needs softening. During this process there is a big problem -the discoloration of denim i.e change in shade or loss of whiteness, giving a yellow tint is commonly known as yellowing. By using normal softener will lead to ozone problem. Indigo dyed fabric are even more prone to yellowing.

As it’s a widespread problem & there in no single reason for its cause. Instead a number of condition can singly or in combination lead to the problem. Yellowing in not specific to certain fibers, finishes or washing processes. It is not specific to chemicals or chemical treatment but certainly some of the factors among these can lead to the yellowing. As cotton & all organic polymers develop yellowing in time.

Light , acids, impurities, detergents & chemical contribute to yellowing problems.

Temperature of drying & curing can impart yellowing due to scorching of the cotton. Therefore good control must be used to minimize this type of damage.

Hence its advisable to use Antiozonate softener which prolong ozone reaction of Indigo & keep garment in good condition.

MINIMISATION OF YELLOWING RISK:

Its Impossible to eliminate yellowing but it is possible to prolong & reduce the conditions which causes classical yellowing:

· Ensure bleaching neutralization & rinsing is proper

· Minimize back staining

· Avoid use of chemicals which cause yellowing

· Avoid leaving garment in open air for longer time

· Control drying & curing temperatures

· Using right Antiozonate softener with right pH

 

About the Author : Saurabh Rai  is a  Textile Chemist by Profession & Denim Finishing Expert .He is working in one of the most well known denim brand in Middle East as their denim washing head. Contact him on email here. Want to write guest articles ? Check here