Articles
Sublimation Blanks Printing Process
by Happy Great happygreat05Long 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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