Short-run custom imprinting can be achieved on a variety
of ceramic and glass substrates through ink jet heat transfer sublimation.
The dye sublimation transfer process begins with a
computer image that, for the purposes of the ceramic and related industries, is
printed to an ink jet printer using special inks and paper. The image can then
be transferred onto an array of hard and soft substrates through a heat
transfer. Aided by pressure, this type of heat transfer converts ink into a
gas, which allows it to migrate into the substrate. As the gas solidifies, it
creates an indelible impression within the final product.
Compared to decorating methods such as pad and screen
printing, which can require high volumes and offer a more limited color range,
sublimation transfer requires no volume minimums or elaborate setups, and
millions of full digital colors can be used. In addition, while the image is
located on the top of the substrate with other technologies, sublimation places
the image underneath a polymer coating, which yields a highly durable decorated
Ceramic tile applications include wall surfacing and inserts
for items such as wood boxes, serving trays, coasters and trivets. A recent
boon has surfaced with the introduction of glass tile. In addition to being
compatible with all uses of ceramic tile, glass is fully walkable and
submersible in water.
Preparing the Substrate
Appropriate substrates include ceramics, porcelain, glass
and stone, as well as items ranging from T-shirts, baseball caps and towels to
jewelry, aluminum and wood. Hard substrates are surfaced with a special polymer
coating, while soft substrates should be constructed of synthetic fibers
(primarily 100% polyester to be compatible with sublimation heat transfer).
Hard substrates (other than stone surfaces) are graded to
be as flat as possible and free of surface anomalies, such as pimples (raised
defects), dimples (recessed defects) or eclusions. Once the substrates are
graded and cleaned so they are free of debris, the proprietary coatings, which
feature a clear polymer base, are robotically sprayed on the surface, and then
heat cured. The coating enables the substrate to be receptive to sublimation.
Without the coating, the dyes would solidify on the surface in no particular
order and simply rub or wash off.
While raw, uncoated substrates are cheap and readily
available, it is often impractical to use common spray- or paint-on polymers
for the necessary coatings. The result is sometimes acceptable, but generally
not. It is very difficult for generic polymers to provide the appropriate
color, consistency, and UV or scratch resistance achieved with proprietary
Sublimation places the image underneath a polymer
coating, which yields a highly durable decorated surface.
The ink used in the sublimation transfer process is a
special mixture of water and heat-reactive dyes. These dyes are available in an
array of four to eight colors, including cyan, magenta, yellow and black.
Depending on the type of ink jet printer used, special light-colored dyes, such
as light black, light cyan and light magenta, are also available.
The familiar "bubble jet" technology makes up
the bulk of ink jet printers currently available. These printers use heat and
pressure as the propellant for their ink. However, sublimation inks become
activated under a heat press, and, as such, do not like to be heated twice
(once onto the paper and again on the way into the substrate).
Thus, proprietary inks call for specialized ink jet
printers. At the time of this writing, sublimation inks are available
exclusively for printers with micropiezo print heads. Printers built to these
specifications fire their ink droplets via pressure under ambient temperature
conditions. Epson manufactures several compatible ink jet printers, including
models C8X, 1280, R800/1800, 4000/4800, 7600/7800 and 9600/9800. Sublimation
solutions for larger, wide-format printers include the Roland Hi-Fi Jet Pro and
Mimaki's JV3 and JV4.
Laser- or light emitting diode (LED)-based printers have
been on the market for some time. However, these types of printers are not as
scalable or readily available as ink jet. Another barrier for market
penetration of toner-based printers is their increasingly vendor-proprietary
toner formulations. In an attempt to thwart the efforts of
"driller/fillers," printer manufacturers are developing toners that
cannot be readily reverse engineered. Unless printer manufacturers slow the
tweaking of their toners, it is not likely that widespread sublimation
alternatives to ink jet will be developed in the near term.
Special inks and printers also require special papers,
and the best of these papers are coated specifically for sublimation. There are
two basic types of paper on the market today: general purpose for most products
and high release for soft products. As the description implies, general purpose
paper yields an acceptable image across a broad spectrum of items. If more color
saturation is required, however, high release paper is preferred.
Many types of sublimation-compatible papers are
available. Some end users prefer only one or two brands of paper, while others
keep and use products from different vendors. The variety allows end users to
experiment with different papers and substrates in order to achieve the desired
Transferring the Image
Heat pressing closes the loop in the life cycle of a
sublimation transfer, using substrate- specific temperatures (365-450°F),
pressures (30+ psi) and dwell times (6-10 minutes for a single item; dwell
times increase along with the number of items). When the ink is heat activated,
it evaporates and then migrates into the polymer coating. As the vapor cools,
it solidifies and reconstitutes itself into a high-resolution, (virtual)
continuous tone version of the original ~200+ dpi dot pattern. For example,
once sublimated, a 300-dpi print can be converted into an image meeting or
exceeding 2400 dpi.
Heat presses can be curved (for substrates such as mugs)
or flat, and their capabilities range from those suitable for hobbyists to
high-volume commercial applications. On a manual press, the user turns a large
nut to set the pressure, then presses down and pulls up on a handle once the
pressing is complete. Alternatively, air-operated presses feature automatic
settings for pressure and timing. The most prominent heat presses are those
from the George Knight Co., Inc. (Brockton, Mass.) and Hix Corp. (Pittsburg, Kan.).
After pressing, the imaging area of the substrate must
not be touched while the item cools. The coating can be abraided or removed if
the item is mishandled before cooling is complete.
General Application Notes
Many variables need to be taken into account in order to
achieve the desired results with sublimation imprinting. Substrates should be
receptive to polymer coatings and versatile enough to be finished with a
glossy, matte or satin appearance. The substrate's surface should be clean (to
avoid dimples, pimples, debris and inconsistent application) and as smooth as
possible to ensure consistent coverage.
In addition, the color of the substrate should be light
or even white, since blank spaces in the image will enable the substrate to
show through. If the decorated item will be used in contact with food or drink,
U.S. Food and Drug Administration (FDA) approval is also required. Additional
- Substrate thickness-the
thicker the substrate, the more time and pressure required to imprint the
- Coating hardness-the
coating should be hard enough to prevent scratching and ultraviolet
- Heat absorption-faster
heat absorption leads to increased productivity. In general, harder substrates
can take longer to sublimate.
Today's digital imprinting offers a platform for ceramic,
glass and related items to be commissioned, enjoyed and preserved. The dye
sublimation transfer process lends itself well to the customization of these
items on demand without extensive advanced planning for the typical job. It is
an economical and cost-effective solution for projects that require
just-in-time turnaround with a high degree of volume flexibility.
For more information regarding ink jet heat
transfer sublimation, contact Condé‚ Systems, Inc., 5600 Commerce Blvd. East,
Mobile, AL 33619-9214; (800) 826-6332; fax (251) 633-3876; e-mail firstname.lastname@example.org; or visit www.conde.com.