Impressions - August 2018 - 25

Screen-Room Best Practices
* Thoroughly clean and degrease all screens.
Remove all ink and tape.
* Measure and maintain screen tension. Set
limits and stick to them.
* Keep it clean and debris-free. Lint on emulsion or vacuum-table glass causes pinholes.
* Coat screens properly. An emulsionover-mesh (EOM) ratio of about 12%-15% is
ideal.
* Control the humidity. Ideally, relative
humidity should be less than 30%.
* Automate screen coating. If you can afford
it, purchase an automatic screen coater for
your emulsion process. This will standardize the screen-coating work in your shop
and reduce that variable.

Write down the recipe for how
each stage of the screen-room work
is completed, such as the products
needed to f ill the dip tank, and how
and where they should be mixed.

able when they are needed. Keep track of your screen room's daily
output and ensure it aligns with your production needs. You can solve
a lot of problems early with this step.
2. Screen Tension: You would be shocked at how many shops
don't understand how screen tension, print quality and efficiency are
related. Regardless of whether you use panel, static or retensionable
frames, the importance of screen tension can't be overstated. Higher tension will produce a better print with less effort than a screen
with lower tension.
A good number of on-press problems could be solved by comprehending the importance of screen tension. For example, if you have
to double-stroke a screen for better opacity, or heat press a print after
production to smooth out the image, you don't have a good handle
on this situation. Spend some time learning this craft.
As a rule of thumb, don't use screens with tensions less than 18
N/cm. Tensions between 18 N/cm and 20 N/cm are suitable for
one-color images, and anything greater than 20 N/cm will work for
multicolor jobs. Screens that are within a tension range of 2 N/cm
of each other for a multicolor job will result in easier registration.
These are basic rules that should be set for your shop.
For increased quality, consider tension rules for each mesh count.
For example, 110 mesh should be tensioned between 25 N/cm and
30 N/cm; 230 mesh should be between 22 N/cm and 24 N/cm; and
305 mesh should be between 25 N/cm and 28 N/cm.

* Use a screen-tension meter. You can't thump
a screen and tell if the tension is decent.
Stop pretending.
* Dial in your exposure times. Use exposure
calculators provided by your emulsion and
screen suppliers.
* Cross-train the art department. Artists
should learn about screen mesh and start
selecting what to use for their images.
Spending time in the screen room and on the
production floor will allow them to see how
mesh choices influence a print. Eventually,
all screen selections should be handled by
the art team, with the screen room filling
the orders.
* Keep track of screen usage. Know how many
screens can be reclaimed, coated and imaged per day, and use this information for
planning.
* The more screens, the better. Once you determine the average number of screens used
per day, ensure three to four times that
many are on your floor. You may need more
than you think, as there will be screens
used in varying degrees throughout the shop.

AUGUST 2018

P.25

Impressions - August 2018

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