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SMR Premium Vellum Tips & Tricks
Most reasons why printers believe they cannot use vellum fall into two categories. Either they think that they cannot get a dense (black) enough image from their computer printer, or they contend that due to shrinkage under the heat of a laser printer's fuser, the vellum shrinks and an adequate alignment becomes impossible. Both of these objections are easily overcome through the use of proper techniques. Inadequate Density - Laser Printer: Many laser printers do not produce a dense enough image on any carrier to expose a screen properly. There are a number of ways to get a better image without getting a new laser printer:
Inadequate Density - Ink-Jet Printer: Most ink-jet printers can produce a vellum image dark enough to burn a screen, but few printers know how to adjust the printer setup dialog to attain an adequate amount of ink laydown.
Tip: Most modern screen printing emulsions do not require nearly as dark of an image as many printers believe they need. Please make certain you know how to determine a correct exposure before determining whether an image is dense enough. Click Here. Laser Toner Flakes Off: While vellum is translucent and might seem to be "Lightweight," vellum is actually one of the most dense substrates you can run through your printer. Toner flaking - which might be observed as dark powder rubbing off from separations, chips in the image, or toner sticking to areas of screens after exposure - is a result of inadequate fusing. Modern laser printers have driver software designed to apply the minimum amount of heat required to prints you make, in an effort to extend the longevity of the heater (fuser) unit, and safeguard delicate papers. The biggest mistake most printers make is in failing to select the paper type when printing vellum, or - worse yet - setting the paper type to a substrate that cannot accept much heat, such as "Transparency." (The "transparency" setting is one of the lowest heat settings on your printer) When printing on SMR Premium vellum you are printing to a substrate that has as much heat-absorption capability and heat-requirement needs as heavy, coated cardstock. You would have a very hard time scorching SMR Premium vellum in your laser printer. For most jobs - and especially when using large sizes of vellum stock - you will want to choose the hottest setting your laser printer can deliver. Heat settings are determined when you set-up your printer by choosing paper types. Look for the thickest, most heat-requiring paper in your printer's setup dialog. Look for choices such as "Thick," "Cardstock," or "Rough." Some older printers do not have paper-type selections. These printers usually run the fuser (heater) at it's highest setting at all times, and usually do a great job on Vellum. However, as printers age, the fuser unit becomes weak, eventually failing. At some point, the fuser becomes too old and weak to properly fuse the toner on vellum. Poor Alignment - Laser Printers: Laser printers use heat to fuse toner powder to the paper carrier. Alignment problems with vellum are caused by paper shrinkage when the laser printer's fuser heats the paper, and humidity in the stock escapes and / or certain elements of the paper itself react to the heat. If the vellum you are using is all cut with the same "grain," then the paper should all shrink relatively proportionately. This means that even though a slight shrinkage has occurred, it has occurred in the same dimensions on each sheet of the separations, so the sheets should still line up. Still other problems are caused by the laser printer's inadequacies as well. Your laser printer uses measurements based on various points of reference to place each dot of toner on the sheet. The fact is, even if your paper were perfectly dimensionally stable, your laser printer would still make some small mistakes in alignment due to which reference points it used to plot one line vs. another. For most screen printed art, using most good-quality laser printers however, this error is negligible. To make alignment problems as minimal as possible:
Poor Alignment - Ink-jet Printers: When you consider that an ink-jet image is created by a paint head running back and forth on a bar, it is a miracle that ink-jet printers can produce pages that line up at all. Yet, most ink-jet printers line up fairly well. Some printers do not reproduce exact sizes well, however, in which case no type of paper or film will be of any help. SMR Premium vellum is relatively moisture resistant, and does not usually shrink in the ink jet printing process. Extremely large areas of solid ink laydown can, however, cause moisture distortion, and jobs with such areas that require tight registration might not be suitable for vellum use. Tip: Before you expose screens in a multi-color job from the vellum positives you have printed, place the positives on a light table and look to see how well they line up. If you placed centering marks in all four corners, most printers find that - if their computer printer is capable of holding good registration - less than 1/100 of an inch of variance should have occurred between separations. That is usually good enough for all but the tightest registration on jobs. If you burn screens from positives that lined up well on the light table, but they don't line up well at the press, then your problem is not in the vellum! Most printers who complain that jobs don't line up (whether they used vellum or other methods of creating separations) fail to get good registration due to factors in the screens themselves, or failure to level screens to the platens and properly use off-contact. Paper Curling: Being a type of paper, sometimes vellum (and transfer release paper) curls up on the shelf. This happens when the paper is allowed to absorb humidity from the air around it. While SMR premium vellum is more resistant to humidity problems than many other brands, small problems can be noticed, especially if pre-shrinking is performed. To avoid curling problems:
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Even
a weak printed image on vellum can be improved dramatically.
After printing on vellum, lightly spray Krylon tm
Artist's Matte finish spray #1311 on the image side of the paper. This
spray is usually available at most hardware stores, and at almost any art
store. A light spray of this substance can make a relatively transparent
image appear dense and black. (You really have to try this to believe it!
It works great!)
