SMR Premium Vellum Tips &
Tricks
Many printers wonder: "Could I really use vellum
and cut my photographic costs?" Most printers who don't believe they can use
vellum have tried, and failed only because nobody had shown them how to
properly use vellum. It is true that not every screen printing job
can successfully use vellum to replace film positives. Extremely fine
alignment jobs, such as 4-color process, and very large sized jobs with
tight alignment needs often disqualify themselves as candidates for using
vellum. However, for most screen printing jobs in the textile and small
signage fields, vellum is usually a better answer than film positives.
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:
- Keep your laser printer in top shape. If
possible, do not use refurbished toner cartridges, as they do not provide
as dense an image as is provided by a factory - fresh cartridge.
- Experiment with your printer to find the
darkest toner setting you can get without toning. Toning is the word used
to describe the gray shading in blank areas when too much ink or toner is
used by a printing device.
-
 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!)
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.
- In the printer setup dialog, most ink-jet
printers ask you to select a type of paper that is being used. Set the
paper type to a very absorbent paper, such as plain paper or card stock.
If your printer has a vellum setting, this is probably not a good
choice for your purposes! Even though vellum is not very absorbent due to
it's extreme density, you will want to select the most absorbent paper
type possible where the ink will not run from the sheet.
- Use regular ink! Many printers have
purchased specialty ink-jet inks for use on film or other substrates.
While these inks work great for their intended purpose, they usually cause
problems printing on vellum. Regular ink-jet ink that you buy off the
shelf for your printer usually works best.
- Use your multi-color ink cartridge if
possible - or when needed. Some (but not many) ink-jet printers have a
dialog in the printer setup that allows you to select to use all four
colors (Cyan, Magenta, Yellow, and Black) when printing black items on the
page. This gives you nearly 4 times the density of ink if you need it.
Most cheaper ink-jet printers come with just a multi-color cartridge, and
you have to purchase a black cartridge separately as an option. If you
don't insert the black cartridge on these models, the printer will create
all black areas by applying all 3 colors, again dramatically increasing
the density of your print.
- Allow adequate time to dry. Vellum is less
absorbent than regular paper, and it takes longer to dry - roughly one
minute per sheet to be "dry to the touch." Make sure that vellum positives
are allowed to dry in a horizontal position (laying down) and that
subsequent sheets emerging from the printer are not allowed to land on top
of previously printed sheets.
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:
- Make certain all papers in a separation set
have the same grain. Never use vellum from two different packages in the
same separation. Also, never "gang" two separations on the same page,
facing different directions.
- For critical separations, pre-shrink the
vellum before printing on it. The best way to pre-shrink the vellum is to
run it through the laser printer before you print on it. Do this by
printing a blank page onto the vellum with your art program, such as by
printing an entirely white object. Make certain you run it twice, once on
each side.
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:
- Store vellum in an area of low humidity. One
strange, yet very well-working solution is to store vellum - well sealed -
in the refrigerator.
- When pre-shrinking vellum in your laser
printer, make sure you pre-shrink once on each side so the
moisture in the paper is treated evenly.
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