The word "Sublimation" is actually a physics word which means changing from a solid to a gas, without becoming a liquid in between. Dry ice changing from frozen carbon dioxide to a gaseous carbon dioxide is an example of sublimation at room temperature.
The dyes used in sublimation toners change from the solid printed form into a gas at about 285F. But there must be a "substrate," a surface which is receptive to the gas, in order for an image to be transferred.
Most commercially sold substrates have a coating intended for sublimation. Coated silver or gold engraving stock is the most commonly used substrate for laser sublimation. The black writing you see on gold metal plaques is an example of laser sublimation. Some plastics are already receptive without a coating, as is polyester fabric, wood and some leather.
The substrates must be heated to be receptive to sublimation gasses. The best time and temperature combination used to transfer and image will change according to the dyes and the substrate used. The dyes used by one manufacturer may be more active than those used by another manufacturer. And there may be variations in potency between different colors of toners from the same manufacturer. Black may be best at 400F, 15 seconds; while red my require 400F, 30 seconds.
Undercooking yields a weak, washed-out image. With black toner, an undercooked image appears purplish or red-ish and has "cratering," the center of the character is washed out. Overcooking makes a blurry image.
Consider what is happening during the pressing process. A piece of paper is held against a substrate and heated quickly. Gasses are formed from dyes sublimating and these gasses enter the heated surface of the substrate. They actually penetrate the surface and become part of the substrate's coating. With some plastics the image is so deep that vigorous sanding will not remove it, to a surprising depth. With metal the image is only as deep as the coating, and that will vary from manufacturer to manufacturer.
With too little time, not enough dye gas will enter the substrate to make a good image. With too much time, more than enough dye gas will try to enter the substrate, but the excess will spill out around the edges of the image, making it blurry.
The greater the temperature applied, the less the time needed to achieve the result. Most manufacturers recommend using a standard temperature of 400F and varying the time to suit your needs. Some dyes are so intense that at 400F they cook well at 15 seconds, but undercook at 13 seconds and overcook at 17 seconds. To allow a greater degree of latitude, you can dial the temperature back to 350F and increase the time to 30 seconds or so.
Pressure has to be great enough to keep the paper tight against the substrate. Too loose and the dyes will scatter when heated, making a blurry image. But a snug, tight fit is all that's necessary.
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The toner used in laser sublimation is a blend of several components. First there is ordinary laser printer toner, the same stuff you use to print out letters. Next there are the sublimation dyes. And then there are charge control additives which affect the darkness of a print. All of this is packaged into particles which are just a few microns in size. The dyes themselves do not have the magnetic or electrical qualities needed to move through a laser printer, they have to be carried by the ordinary toner.
This is why a used transfer paper still has a strong image on it. The ordinary toner is still there, but the dyes have left.
But the ordinary toner presents a problem, in some instances. It leaves a residue behind. During pressing, some of the toner sticks to the substrate. The dyes actually enter the surface, but the toner sticks to the surface.
When using metal as a substrate, many people press through the protective plastic which covers metal. The sublimation dyes go through the plastic but the toner residue does not. So when the paper is removed from the pressed metal, the protective plastic and all the toner residue is removed as well.
Pressing directly on to the metal, with the plastic removed will usually result in a somewhat sharper image. The thickness of the plastic allows dyes to disperse somewhat. However, this requires cleaning off the residue with a citrus cleaner.
Toner residue can be reduced by pressing at a lower temperature, such as 300F, for a longer time.
With most sublimation toners a very good image can be obtained pressing through the plastic, if you take care to find the exact time and temperature for your substrate and your equipment.
USING A STEAM IRON (if you don't have a heat press)
First, turn off the steam. Set it at the highest setting. Select a hard, even, flat surface which will not be damaged by heat. Formica type counters work well. Cover the work area with a dishtowel or some other cloth which has some thickness but not the cushioning of terry cloth. Place a large empty trash container near your work area, and expect to use it while learning this.
Use heat-resistant tape to secure the paper to the substrate. Heat-resistant tape can be purchased from most sublimation suppliers. If you don't have it, find some other way to prevent the paper from moving around on the substrate while you move the iron. With small work you can fold the paper over the substrate, but be careful to not make a bulge on the back which will affect your ironing.
Try to apply even pressure, and move the iron in circles. Irons have uneven heating surfaces and you have to move them to prevent cold spots from damaging the image. Figuring out your times and procedures is largely trial and error. Start by trying to overcook, say around three minutes, and examine the results.
Over to you, good pressing. |
Hilton
Images, Inc.
Finest Quality Laser Sublimation Products