Proceso de sublimación Blanks Printing por Elaine Estelle

Long runs of the same fabric design are produced on a roller print cylinder

machine operating at speeds between 50 and 100 yards a minute. As many as

10 different colors can be printed in one continuous operation, but each color

must have a separate roller. The design is cut into the surface of copper rollers;

by varying the depth of the engraving on the roller the shade depth can be

altered. Sharpness of line and fine detail can be achieved this way. A typical

printing machine has a large padded drum or cylinder, which is surrounded by

a series of copper rollers, each with its own dye trough and doctor blade that

scrapes away excess dye.

In flat screen printing, a screen on which print paste has been applied is lowered

onto a section of fabric. A squeegee then moves across the screen, forcing the

print paste through the screen and into the fabric. The screen is the image

carrier made from a porous mesh stretched tightly over a metal frame. A

positive stencil using negative art work is produced on the mesh either manually

or photo chemically. Ink is then forced through the fine mesh openings using a

squeegee that is drawn across the screen allowing print paste to pass through

only the areas where no stencil is applied.

Block printing is a traditional process dating back to India in the 12th century.

Wooden blocks made of seasoned teak in different shapes and sizes are cut by

trained craftsmen. Each block has a wooden handle and two or three holes

drilled into the block to the passage of air and release of excess print paste.

Fabric is stretched over a printing table and fastened with small pins. Printing

starts from left to right, first the color is evened out in the tray and then the

block is dipped in. Then the block is applied to the fabric with careful

registration and pressure is applied.

Multiple color designs are labor intensive and require a lot of skill to register

the prints exactly. Color variation is hard to avoid with this method as print ink

can vary in quality of depth or color. The Japanese took wood block printing to

new levels and developed unparalleled skill in the construction of fine delicate

prints.

This is essentially transferring an image to fabric from a paper carrier. When

heat and pressure are applied to this transfer paper the inks are transferred.

Some transfers are topical, and the image sits on the surface of the fabric. Other

transfers are absorbed into the fibres of the fabric. Heat transfer printing is

clean and environmentally safe. The only by-product is the paper carrier. It is

the perfect print method for short run and sample production, but can also be

used for batch production as well.

Dye sublimation allows photo lab quality picture printing. During the dye

sublimation printing process, an image is digitally printed in reverse with dye

sublimation toners or inks onto media. That image is then placed on top of a

fabric and subjected to high heat and pressure to form a heat press. The dye

sublimation toners or inks sublimate – the inks go from a solid state to a

gaseous state without becoming liquid in between and flow into the fabric,

dyeing the threads. This creates a gentle gradation of colour and does not

distort or fade over time.

Discharge printing is one method of resist printing and involves using a

chemical paste called a disperse dye. It must be used with a ‘reactive dye’

as a ground color for the process to work. It also has to be ‘cured’ or fixed with

steam so the dye reacts with the fabric and causes a color reaction. Discharge

printing produces the brightest, lightest prints on dark-colored garments and

can be very striking. This method can only be used on natural fibres and fabrics

that will discharge color. Another method of resist printing is Batik. Natural

materials such as cotton or silk are used as they absorb the wax that is applied

in the dye resisting process. The fabrics must be of a high thread count (densely

woven) for best results.

After the wax has been applied, the fabric is ready for the dye bath. Today most

batik factories use large concrete vats, above the vats are ropes with pulleys

that the fabric is draped over after it has been dipped into the dye bath. The

amount of time it is left in the bath determines the hue of the color (longer for

deeper colors)

The most commonly used processes for imparting color to cotton are piece

dyeing and yarn dyeing. In piece dyeing, which is used primarily for fabrics

that are to be a solid color, a continuous length of dry cloth is passed full-width

through a trough of hot dye solution. The cloth then goes between padded

rollers that squeeze in the color evenly and remove the excess liquid. In one

variation of this basic method, the fabric, in a rope-like coil, is processed on a

reel that passes in and out of a dye beck or vat. Yarn dyeing, which occurs

before the cloth is woven or knitted, is used to produce gingham checks, plaids,

woven stripes and other special effects. Blue dyed warp yarns, for example, are

combined with white filling yarns in denim construction.

One of the most commonly used yarn-dyeing methods is package dyeing. In

this system, yarn is wound on perforated cylinders or packages and placed on

vertical spindles in a round dyeing machine. Dye solution is forced alternately

from the outside of the packages inward and from the inside out under pressure

. Computers are used increasingly in dyeing processes to formulate and match

colors with greater speed and accuracy.

Finishing, as the term implies, is the final step in fabric production. Hundreds

of finishes can be applied to textiles, and the methods of application are as

varied as the finishes. Cotton fabrics are probably finished in more different

ways than any other type of fabrics. Some finishes change the look and feel

of the fabric, while others add special characteristics such as durable press,

flame resistance, shrinkage control and others. Several different finishes may

be applied to a single fabric.

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