Different Types of Dry Process for Denim Wash
Md. Mizanur Rahman
Daffodil International University, Dhaka
The distressed jeans that we see around everywhere undergo a wide variety of wet as well as dry treatments to get the desired effects. Destroying denims is as much an art as it is a technique. The direction in fashion is varied across all areas particularly in denim dry process, whether worn or torn to wrinkled or pressed; these trends can appeal to a wide range of consumers. These can be achieved by variety of denim dry processing techniques which are mainly dependent on physical and on chemical abrasion of the surface dye there by producing different wash-down looks to the denim fabrics. Hot spots are heavy/intense area on thigh or knee, which is made purposely to create used-look & on knee area if any whiskers lines are there, called knee star.
Different Types of Dry Process for Denim Wash
Whiskers are one of the most important dry process of denim wash bringing used look garment. The idea of whiskers is taken from the worn out lines and impression patterns generated by natural wearing on hips and front thigh area. On old jeans, a number of patterns can be finding consequential to fabric, body shape of user or sitting posture. It is also known as Cat’s Whisker.
Various methods are designed to create this impression on jeans. Such as:-
Mostly rubber balloons are available with different pattern designs. Garments are mounted on balloons and filled with air to get impressions of whiskers. Garment is scrubbed over pattern carefully with sand paper on engraved pattern lines. This operation requires high skilled labor and who can handle uniformity and sequence in whisker line. Fabric may damage during rubbing if care is not taken. This method is famous for high quality and cost effectiveness.
Sometimes separate patterns are made and fixed on balloons to make mustaches. These patterns are made of thin rubber sheets and electric wires or rubber cords and pasted on balloons for pattern lines. Thin line patterns are very easy to work in that way but it is not much successful for broad lines.
Engraved patterns on thick board like hard rubber sheets are widely used for whiskers impression making. This idea is very simple to draw lines on rubber sheets and engrave them with blade. Garment is places on sheet and scrapped on specific area to draw this impression on garment. For its low cost patterns, it is most frequently used in small industries especially where the production is not consistent to style.
In some workshops it is done manually with the help of sharp edge rolled on fine wood sticks of pasted on plastic material. Before starting execution, placement and pattern must be marked on garment, this will help operator to execute the pattern right to match the aesthetics of garment. 
Sand blasting is the process of scrubbing off the garment by blowing high-speed air mixed with very fine particles of sand. This is a very successful and most widely used process for fashion articles. When the surface area of the garment is blasted, white cotton appears beneath the blasted area and the effect appearing is very similar to the worn out jeans. Sand blast provides a very uniform result, which cannot be achieved with its alternates. Its specialty is the merging effect that is blended with such a beauty that it has no difference with natural effect.
High pressure of air produces a powerful backward thrust to operator so it is always recommended to fix the gun in appropriate stands rather than placing it on shoulders or using it with bare hands. On some fabrics sand blasting is not successful for it covers the characteristics of fabric. Especially in fabrics, which are famous for slob patterns it flattens the look. Specified areas for sand blasting are front thigh, back seat, back panel near bottom or front panel around knee. Some time full body blasting is also done for giving a unique look to fabric. Hot spots may be designed for more real look on front knees or back seat by intense blasting in these areas.
Procedure of Sand Blasting:
- Individual garment to be processed is taken on a table.
- Air compressor is started and pressure to be maintained between 3 – 4 kg/sq.cm.
- Air compressor then stores air in the machine cylinder. Aluminum sand or silicon sand, Al2(SiO4)3, is then taken in the chamber of the blasting machine.
- Sand and compressed air are then sprayed over the garments at specific points at 10-200 angle by hand spray pipe.
- Sands pass into the machine by regulating system.
- The machine comprises a blasting regulator and a hand regulator to control the amount of sand and compressed air respectively.
- The angle of sand blowing is very important. Higher the blowing angle, higher the fading effect and higher the risk of fabric damage.
- Fading is done on pre-marked areas.
- Sandblasting is a hazardous technique and therefore, the area should be isolated from other working areas.
- Handling of sandblasting gun is risky therefore, operators should use safety equipments like hand gloves, mask and gown. Production/hour/gun varies from 25 – 45 garments depending upon the degree of fading or extent of fading to be attained.
- The faded garments are cleaned by shaking manually. After sandblasting, garments are washed and the technique is being followed may be normal, bleach or bio-stone. 
Potassium permanganate spray (P.P Spray):
Potassium permanganate spray is done on jeans to take a bright effect on sand blast area. One important thing about potassium permanganate spray is, this is usually a sporting process to increase the effect of sand blast. Potassium permanganate solution is sprayed on blasted area of jeans garment with the help of normal spray gun. This potassium permanganate spray appears pink on garment when fresh and turns to muddy brown on drying. The garment is hanged in open to dry after potassium permanganate spray and when the potassium permanganate turns its colors completely then it is considered to ready for next process. It is always followed by neutralization process. Sodium Meta bisulphate is most commonly used neutralizer. A number of products are available in market for neutralization process like sodium Meta bisulfate selected on the bases of effect required on blasted area.
Potassium permanganate sprays concentrations ranges from 0.25 gm per liter to 15.00 grams per liter depending to required results and fabric types. Usually indigo died fabrics are treated with low concentrations whereas Black Sulfur Fabric requires high concentrations to treat with.
Process of P.P Spray:
1. Potassium permanganate spray in best is done in specific spray booths, where rubber dummies are installed for holding garments. Garments are mounted on the dummies and air is filled so the garment is full fit exposed. Specific dummies are used for different sizes and styles, like for kids, men’s, trousers, jackets, shirts etc. The booths are fitted with proper air exhaust system. This system leads the spray to treatment room where the chemical mixed air is usually passed through the water showers. Potassium permanganate is dissolved in water and the clean air is blown to open. Shower water is further treated with mild quantities of neutralizer before adding to main drain. But where the potassium permanganate spray is used in low concentrations then there is now need to treat shower water. This mild potassium permanganate mixed water is rather useful for water reservoirs to keep the water clean and germs free.
2. Garments are mounted on air-filled rubber dummies and chemical is sprayed on blasted areas. The variables in spray process are as follows:
- Distance of spray gun to garment: Less distance will give more defined and sharp effect whereas distant spray will result in more mild and merged effect. Distance ranges from one foot to two and a half feet.
- Air to water ratio of gun: This is to be set very carefully. Low air pressure possibly will through KMnO4 drops on garment resulting in bright white spots whereas high pressure will produce very low bright effect spray effect to areas where it is not required.
- Potassium Permanganate Solution Concentration: This will control the extent of brightness.
Potassium Permanganate Sponging/ Brushing:
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 sponges 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.
In usual, it is done with regular paint brushes or the brushes are modified by cutting hairs in different shapes to produce new styles. Rather towels, sponges, straw bunches or other objects are also used to create effects. What it is seen, is that most merging and beautiful effects are created with towel. Towel dipped in solution are drawn over the garment very lightly. This produces random effect and looks great with dark washes in contrast.
This process is very complicated & needs highly skilled operators to execute it followed by immediate neutralization.
Procedure of P.P Sponging/Brushing:
- Prepare Potassium Permanganate solution.(P.P 20%,water 80%).
- Take the solution in a tray or bowl.
- Take a rubber board.
- Then take a jeans trouser & place the rubber board inside the leg panel of the trouser.
- Now place the trouser with rubber board on a flat table & sponged or rubbed P.P on apparel surface.
- Then color will faded.
- After this process wet process essential (detergent/bleach/enzyme wash).
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.
Different types of machine used for destroy the garments. Such as-
- Grinding Machine.
- Emery Cloth.
- Hacksaw Blade.
- Knife etc.
Process of Destroyed Denim:
- We can make holes in jeans by overdoing different methods. The trick is to make the holes look natural. Grind away at the fabric slowly. Try not to localize the worn area, spread it with diminishing wear the further we get from the intended hole.
- The area around the hole should be worn out as well as bleached to further blend the hole with the surrounding fabric. “Finish” the edges with a pumice stone or sandpaper dampened in bleach. Also dampening a sponge with bleach and applying it to the outer edges of the hole will add to the natural worn look.
- Ripped jeans are a bit different. The rip is not necessarily from wear, and should not look the same as a worn out hole.
- It is important that what types of look we want to see on our denim. It is recommend to use a sharp pocket knife. Be careful, they are very sharp. Rub the blade of the knife perpendicular to the line of the rip that we want. Continue until we create a slit, and then fray the edges, exposing the threads that are perpendicular to the rip. Do this until the hole is the size that we want and the edges are fuzzy. A wash and a dry will further mess up the edge. To some extent this will control further fraying.
- To reinforce this newly created hole, turn your pants inside out and place an adequately cut piece of fabric around it and sew it. An iron on will work as well, but the stitching, done either by hand or with a sewing machine, will make it look much better.
- It is preferred that not too many holes, 3 to 5 should be enough. The current trend, however, seems to be for smaller holes.
The scope dry process of denim wash is very broad. Only innovative products will be able to open up new markets and new horizons for denim industry. To achieve this it is essential to invest in further research and development. Globalization has opened the door to competition at the highest level. Every industry should now produce products that are best in terms of quality and price. Customers today have a wide range of choices and the one who produces the best quality at a high competitive price will survive and prosper.
- http://www.denimsandjeans.com/denim/manufacturing-process/denim-dry-processing-for-creating- vintage-jeans/
- http://www.denimsandjeans.com/denim/manufacturing-process/denim-dry-processing-for- creating-vintage-jeans/
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.