Common Printing Defects in Screen or Roller Printing

The following printing defects are frequently observed in screen or roller printing:

1. Scrimp

 During the printing process the fabric sometimes creases under one of the screen during the printing process. Thus the pattern is printed on the top of the screen. When the crease is removed, it leaves a large area of the fabric unprinted.

2. Misfit or Out of Registration

 A misfit is a defect caused when screens are not properly aligned. The misaligned screens can leave an area unprinted or cause the pattern overlap on one another.

3. Stick-in

A stick-in occurs when a small fiber or yarn get stuck in one of the screen openings. It can result is a small unprinted circle in the design of the size of the tip of a pen. A stick-in is very  difficult to see and often go unnoticed.

4. Wicking or Flushing

It occurs when the printed area bleeds out into the unprinted area. This results in a "haloing" or shadowing effect around the outline of the pattern design. Wicking is often caused by residual salts left in the fabric during  resign finishing or during fabric preparation.

5. Doctor Streak

It refers to a wavy white or colored streak in the fabric in the warp direction. It is called so because it is caused by damaged or improperly set doctor blade in the printing machine. A doctor blade is a metal knife that cleans or scrapes the excess dye from engraved printing rollers, leaving dye paste only in the valleys of engraved areas.

6. Mottled

It results from the color applied unevenly during printing

7. Printing Machine Stop

As a result of printing machine stop the dye sometimes is smudged along the width of the fabric.

An excellent description of defects in digital printing can be found here.

Thanks for your attention. Did you find the information you were looking for ? Please leave a comment. Do you need to know more ? Please suggest a topic in the comments. You can also join the Forum for your specific queries.

What are Plisse and Burnout Prints

Plissé Prints

The plisse prints are created by application of strong alkali to 100% cotton fabric. The alkali is applied in a pattern. After some time ( usually several minutes) the fabric is washed so that the alkali is removed. This results in the shrinkage of fabric from those areas where alkali is applied. This shrinkage causes puckering in the areas where alkali is not applied. A seersucker type appearance can be given to the fabric by applying the print pattern in parallel stripes. The alkali can be applied using direct or resist methods. 

http://ny-image0.etsy.com

Burn Out Prints

A beautiful "burn out" effect can be created by applying strong mineral acids or acid salts in the selected areas of a cotton polyester blended fabric. The acids will cause cotton to be destroyed and the polyeste rremains. Thus very beautiful lacey designs can be imparted to the fabric. Also in the burn out paste, a disperse dye can be incorporated which will also dye the polyester which burnout is taking place. However, due to the corrosive nature of the process special protections need to be taken.

Thanks for your attention. Did you find the information you were looking for ? Please leave a comment. Do you need to know more ? Please suggest a topic in the comments. You can also join the Forum for your specific queries.

Effluent Tratement- Kerosene Recovery from Pigment Printing

Effluent Treatment- Kerosene Recovery from Pigment Printing

In India about 46% of the total printing is done using pigment printing method, 27% using reactive dyes, 15% Disperse dyes, 2% napthol, 3% acid and 7% using vat colors.

In a typical pigment printing paste, 75% is keorsene, 10% is binder, 5% each is gum and water, 2% urea and 1% each of DAP and emulsifier. Kerosene water emulsion acts as a thinkner is pigment printing. Its use is prohibitied in most of the developed countries. Alternatives to kerosene are synthetic thickners but they make the printed fabric stiff.

In India alone, about 140 thousand kiloliters of kerosene per annum is consumed during the process of printing and drying. Out of the total kerosene applied, about 22% is lost at various points during this process( 1 % is left out on the fabric, 12% screen printing and wastage, 5% is before dryer, 4% is at curing machine and 78% is released or evaporated in the atmosphere during the process of drying at 120-150 deg C). It signifies a loss of precious kerosene as well as pollution in the environment.

Apart from the effluents generated during wet processing, there is a substantial amount of kerosene vapour that is released in the air in the process of pigment printing.

Any kerosene recovery process should be based on the fact that kerosene is liquid at room temperature and immiscible with water. The kerosene vapour are at 120 deg C and they have to be cooled below 40 deg Celcius. The kerosene and water will separate out in two layers, with top layer can be skimmed for reuse.

An excellent effluent treatment plant is proposed by BTRA. Average recovery is 58% whereas maximum recovery can be 85%. Read more about it here

To view the pigment printing process and alternative to kerosene, please find the link here.

Thanks for your attention. Did you find the information you were looking for ? Please leave a comment. Do you need to know more ? Please suggest a topic in the comments. You can also join the Forum for your specific queries.

Puff Printing

Watch these Videos on Puff Printing



Here is the industrial version of it:



Now that you've finished reading this post, what are you going do? You should go join the Forum.

Heat Transfer Printing

Watch this amazing video on Heat Transfer Printing



Now that you've finished reading this post, what are you going do? You should go join the Forum.

What is High Density Printing

High Density is a popular special effect that rises straight up off the shirt and has a hard rubbery feel with sharp edges. A High density print has slight glossy finish.

The source of this image is Anomaly Ink.

To get these effects about 20% of the puff base is taken which is then mix with colored inks to make it 100%. The base is Vinylidene chloride based polymer and the inks are Acrylic co-polymers. 

Then it is printed in 5-8 rounds depending upon height required on normal screen ( 2 flood/ 2 strokes). After that 3 rounds of printing is given with 150 micron film screen and then 2 rounds with 220 micron capillary film screen depending upon the height. 

An excellent video on flooding and stroking is embedded as below:

Now that you've finished reading this post, what are you going do? You should go join the Forum.

What is Glitter Printing

Glitter Printing

Glitter printing enables the fabric to show glittering granules on the fabric. For this Glitter powder is used.

Glitter Powder is generally PET with size of 1/8" to 1/256". It is cut into square and hexagon shape. It is available in metallic, rainbow, laser and iridescent colors. Generally it comes in 25 kg bag. A typical glitter power substance is heat resistant to 170 degree celcius and is acid and alkaline proof. The picture of the glitter powder is as given below:

To Print, first glitter paste is prepared. Glitter powder is added in the Glitter ink, under stirring slowly to avoid lumb formation. Glitter ink is made of acrylic co-polymer. Then it is screen printed using Bull nose squeegee (You can read an excellent manual on squeegee here.) The mesh size should not be more than 20 T (An excellent premier on mesh size can be read here).

One can get an idea of the prices of the chemicals used for glitter printing here.

Source of Picture: http://www.ampmerch.com


Now that you've finished reading this post, what are you going do? You should go join the Forum.

Traditional Dabu Printing of India

Dabu is a mud-resist hand-block printing practiced in Rajasthan of India. The prints have a sublime quality and appearance. In making of the printed fabrics, a lot of manual process and hard work is involved and the process of uses lots of natural dyes and vegetable pastes. Here is a brief outline of the process.

1. First of all Fabric is received from the mills. Traditionally mill made cloth of 30s, 60s and Mull is used.  It is heavily sized. For that it needs to be desized. Desizing is done by repeatedly beating the wet fabric against a hard surface (stone). It is frequently kept for a day after such beating so that enzymatic reaction can loosen the size. Next day it is again beaten and so on. This process continues for three days. 

2.  After that the fabric is dipped in Myrobalan (Tanning) agent. The myrobalan paste is prepared about three hours in advance by mixing about 2kg paste for 100 m of fabric.

3.After that the fabric is dried in the sunlight

4. After that fabric is printed once with a paste of Alum+ Tamarind Seed+Direct dye to distinguish. (Red Process-No Dabu)

5. After that fabric is washed once, and then it is dried and then go for boiling.  In boiling we boil the fabric with Dhauri Ke Phool ( Jaloor)+ Alizarin ( Madder)+Mahi for 1 hour at 100deg Celcius. The fabric is circulated about 5 times using Bamboo Poles. If the color required is dark then some iron water needs to be added.

6. After it is dried and then the next process of Dabu is done. Printing paste is made using ( Jaggery, Hydrate of Lime, Kali Mitti and Gum ( Nigeria). The paste is then spread over a coir to give it a base. The printing is done using blocks. (White Process-Dabu).

Saw dust is sprinkled over the fabric as it is printed so that the block applied should not smear the other sides

1.       Then it is dried in the sunlight. 

After that the fabric is treated with Myrobalan again.

                                           

3.       Then it is dried and then dipped completely in Alum + Water.

4.       Then it is dried and washed and again boiled with Alizarin+ Mahi( Sakur)+ Dhawdi. Then it is dried in the sun and washed to reveal the dabu resist .

Want to see something modern in Dabu ?? Klick here.


Now that you've finished reading this post, what are you going do? You should go join the Forum.

Comparison of Various Printing Techniques

Comparison of Various Printing Techniques

There are various printing techniques available. All have their unique points as well as shortcomings. It would be worthwhile to compare them in order to appreciate and use them for a particular end use.

Handblock Printing: It yields very low production, there is more downtime of ‘machine’. The cost of set up is very less. Very skilled personnel is required to do such printing. The cost of making a design is very less, however durability of design is very low, being defined by durability of block, usually made of wood. The variety of designs is dictated by the skill of the woodworker who carves those designs. The size of design pattern repeat can be larger. There is a limitation of width of the fabric- which is dictated by the width of the table. The printing can be very bold or subdued. In fact, in India there are numerous techniques based on a twin combination of natural dyes and block printing.

Roller Printing: Yields more production , machine downtown is very less, however cost of setup is high- as investment is needed for the maching. The space required is less. Again very skillful operators are required. The cost of making a design is more, as roller has to be carved. The durability of the design is more than a handblock print. Very elaborate and fine designs can be carved on a roller printing. The repeat size is limited to upto 42 cm. Again it has a limitation of fabric width. Very bold and lustrous prints cannot be done on a roller printing.

Flat Bed Screen Printing: Yields more production but less than roller printing as the process is not continuous. There is very less downtime of the machine. The cost of machine and installation is very high. The space requirement is also very high. Very less skilled workers are needed for this printing method. The cost of making a design is less as compared to a roller printing. The durability of the design however is very less, as new screen has to be made after few uses. The quality of designs can be very fine. The repeat of pattern can be very high. Also even a higher width cloth can be printed. The colors can be very bright and bold.

Rotary Printing: It has the maximum production among all printing techniques. The machine downtime is very less. The cost of machine and space requirement is again very high. Less skilled workers can be employed to operate this machine. Cost of making a design is very high. Compared to this the durability of the design is very less. The variety of design it offers and the quality of reproduction is the best among all techniques. Also fabric width can be high for it to be printed. It can yield bright colors.

Transfer Printing: It can do printing only on synthetic fibers such as polyester. One cannot get a ‘tone effect’ in this printing. Even unskilled workers can be used for this technique. However 100% color is not transferred so reproducibility is affected. Paper can’t be used again after one printing therefore its durability is the minimum of all techniques. The cost of making a design is very high. The production is about equal to that of flat bed. There is very less downtime of the machine. Space requirement is very less, infact, less than any other printing technique.

Now that you've finished reading this post, what are you going do? You should go join the Forum.

Printing with Natural Dyes

Printing with Natural Dyes

In traditional methods in India, printing is essentially carried in three steps:

1. Preparation of the Cloth
2. Mordanting
3. Dyeing

1. First of all the cloth is prepared by applying tannin.

2. A thickened mordant is printed on this tannin treated cloth in the desired pattern.

3. The cloth is then dyed so that dyestuff attaches itself to those parts of the cloth to which mordant has been applied.

Thus the various processes are:

a. Tanning of fabric
b. printing of mordant
c. fixing of the modant
d. washing out the excess of fixing agent
e. dyeing
f. washing and soaping.

Harda or Myrobalan is used in India as a tanning agent for dyeing and printing with natural colours.

It is applied on scoured cotton fabric in cold ( 10-40 gpl) using conventional method of tub dip wherein the Harda powder is replenished with each piece added to the bath.

After drying various metallic salts such as alum or ferrous sulphate are printed on the fabric either separately or in mixtures.

It is then subsequently dyed with madder root ( Manjith), pometranate rind, kusum flowers and other vegetable dyes.

Common Problems in Pigment Printing

Click here for common problems in pigment printing and their causes.

New Developments in Dyeing, Printing, Finishing

Please see the link here or here for New Developements in Dyeing, Printing and Finishing.

Textile Printing-1

Printing has often been described as dyeing in a localized, patterned design. Textile printing utilizes the same dyes or pigments applied to produce a dyed fabric.The same principles of specific dye classes having select fibre affinities and the general fastness characteristics apply equally to printing as to dyeing.

Dyes or pigments used in dyeing are usually in a water bath solution. When the same dyes or pigments are used for printing, they must be thickened with gums or starches to prevent the wicking or flowing of the print design.The thickened solution, about the consistency of heavy buttermilk, is called the print paste.

Many dyes cannot be used in printing pastes. Some of the reasons include insufficient solubility, Low colour yield and poor print paste stability.

METHODS OF PRINTING
There are several methods for printing of textiles. Two are of significant commercial importance: the roller print method and the screen print method. A third method, heat transfer printing, is of less significance. Other printing methods, not widely used in commercial production of textiles, are block and batik printing.

Roller Printing

This method of printing is comparable to newspaper printing. It is a high speed process, capable of producing over 6000 yards of printed fabric per hour. The method is also known as machine printing.

In roller printing, the design is put into fabric by copper engraved rollers (sometimes called copper engraved cylinders). The roller engravings match exactly the artist-designer's creative sketch. A separate engraved cylinder is required for each colour in the print. The size of the engraved cylinders is governed by the printing machine and the design.

HOW ROLLER PRINTS ARE MADE

1. The Engraved Copper Roller A in rotation makes contact with Colour Furnisher B (whose surface is much like that of a paint roller used in house painting). The entire surface of Roller A becomes covered with print paste.

2. Colour Furnisher B, also in rotation, picks up a constantly fresh supply of print paste from Colour Box E.

3. Meanwhile, Engraved Copper Roller A in rotation comes in contact with Doctor Blade C. This is a steel blade which functions somewhat like a squeegee. It scrapes off all the print paste on the surface of Roller A, but cannot clean off the print paste from the engraved portion, and thus leaves behind the print paste inside the etched copper.

4. The cloth to be printed is drawn and guided between the Cylinder Roller and Engraved Copper Roller A. The pressure created at the point of contact causes the print paste to be transferred from inside the etched copper to the cloth. The pattern is now on the cloth.

5. Engraved Copper Roller A continues in rotation and comes in contact with Lint Doctor D, a steel blade which comes in contact with Roller A and removes any lint picked up from the fabric being printed.

6. The cloth being printed continues its path around the Cylinder Roller. If a 2nd, 3rd or 4th colour is to be printed on the same fabric, then Steps 1 through 5 will be repeated for the respective 2nd, 3rd or 4th sets of Engraved Copper Roller, Doctor Blades, Colour Box and so forth. The fabric makes only one pass through the roller printing machine. Successive colours do not become smudged because the pressure of the engraved roller on the fabric being printed literally squeezes the print paste into the fabric and the surface colour dries instantly.

7. The printed cloth on leaving the machine is immediately dried so that the fabric can be touched without smudging the print. Afterwards, the fabric is transferred to a steam chamber where moisture and heat will set the dyes. If pigments rather than dyes are used, the fabric is entered into a dry heat curing oven at temperatures up to 400°F.

8. 'The Back Grey is a fabric that moves through the print machine along-with and in back of the fabric being printed. Its function is to absorb the excess print paste which may strike through and stain the Cylinder Roller cover. The Back Grey is later washed out and used over and again. It eventually takes on a dingy grey colour, hence its name.

Screen Printing

Screen printing is a method whereby an open, but closely meshed screen, mounted in a wooden or metal frame, is placed in contact with the fabric to be printed and the print paste forced through the screen by a squeegee (implement edged with rubber for sweeping water from surfaces). The design is created by painting out or otherwise making opaque portions of the screen, thus preventing the print paste from passing through. Those areas where the print paste does pass through will register as the printed pattern.

There are actually three methods of screen printing, each of which embodies the same principle. The first, hand screen printing, the second method is automatic screen printing or flat bed printing or automatic flat printing and the third method is the rotary screen printing or rotary printing.

Hand Screen Printing

Hand screen printing is done commercially on long tables (up to 60 yards in length). The roll of fabric to be printed is spread smoothly onto the table, whose surface has first been coated with a light tack adhesive. The print operators then move the screen frames, by hand, successively along the whole table, printing one frame at a time, until the entire fabric is printed. Each frame will contain one colour of the print. A three colour print, for example. will require three frames and three applications to the fabric. The rate of production ranges from 50 to 90 yards per hour by this method.

Automatic Screen Printing (Flat Bed Printing)

Automatic screen printing (flat bed printing) is like hand screen printing except that the process is automated and therefore, faster. Instead of the long table on which the fabric to be printed is spread (as in hand screen printing), the fabric is moved to the screens on a wide rubberized belt. Like hand screen printing, it is an intermittent rather than a continuous process. In this instance, the fabric moves to the screen, then stops for the screen squeegee action (which is done automatically). After the squeegee action, the fabric moves again to the next screen frame. The rate of production is about 500 yards per hour. Automatic screen printing is utilized for whole rolls of fabric only.

Rotary Screen Printing

Rotary screen printing is different from the other methods of screen printing in several important respects. Rotary printing is continuous like roller printing. The fabric being printed is moved on a wide rubber belt under the rotary screen cylinders which are in continuous movement. Rotary screen printing is the fastest method of screen printing, with production of 2500 to more than 3500 yards per hour. Seamless, perforated metal or plastic screens are used. The largest rotary screens have a circumference of about 40 inches and the maximum repeat size of patterns is, therefore, about 40 inches.

Heat Transfer Printing

Heat transfer printing is sometimes called thermal transfer printing. In this method, the design is first printed on paper with printing inks containing dyes of the disperse dye class. The printed paper (called transfer paper) is then stored until ready for use by the textile printer or converter.

When fabric is to be printed, it is passed through a heat transfer printing machine which brings paper and fabric together face to face and passes them through the machine at about 400°F. Under this high temperature, the dye on the printed paper sublimates and is transferred onto the fabric.The process, resembling somewhat the familiar decal transfer, is relatively simple and does not require the expertise necessary when producing roller or rotary screen prints.

Disperse dyes are the only dyes which can be sublimated. and thus the only ones which will respond in a way that permits heat transfer printing. The process is therefore limited to fabrics which are composed of fibres having affinity to this class of dyestuff. This includes acetate, acrylics, polyamides (nylon) and polyesters.

The Above table give a list of the printing methods and their advantages and disadvantages.

PRINTED FABRIC IMPERFECTIONS

The following is a listing and description of the more frequently occurring imperfections that may result from printing processes. These imperfections may result from faulty or improper printing procedures, faulty or improper preparation of the fabric prior to printing or to imperfections in the material being printed.

Since the printing of textiles is in many respects similar to the dyeing of textiles, many of the imperfections found in dyed fabrics are also found in printed fabrics.

A. Colour Drag- Colour of the print smears or smudges from rubbing against an object before it becomes dry.

B. Colour Splatter-The print paste instead of being placed on the fabric is thrown or splattered onto the fabric surface.

C. Fuzzy Pattern - The edges of patterns are not sharp, clear lines, but are instead rather fuzzy lines. Most frequently caused by improper singeing or improperly thickened print paste.

D. Off-register- Printing rolls or screens improperly aligned so pattern parts do not meet properly. This imperfection is also called out-of-fit or out-of-register.

E. Stop Mark- Colour streak across the fabric resulting from the printing machine being stopped during the printing process and then starting again.

F. Tender Spots- In printed fabrics, one or more colours of the print may cause weakened areas where they were printed. Usually due to excessive use of injurious chemicals in the print paste. May also be found in the discharged area of discharge prints.