Mark Twain once sarcastically responded to the tabloid articles of his day with the assessment, “rumors of my demise are greatly exaggerated.” Such is the case today with sign shop screen printing. Rumors of its demise are greatly exaggerated, too.

Sign shop screen printing can be as simple and inexpensive as this little manual printing arrangement (left)......or involve semi-automatic presses like this Saturn press by M&R, or larger units (right).

While some sign makers might believe this tried and true medium of producing quantities of outdoor durable signs and decals is on its way out because of today’s digital printing equipment, other modern sign businesses could not service their customers nor maintain their profit margins without it.
What’s the unbiased truth on this subject, and how might that truth affect your sign business? Let’s use “Shop Talk” this month to consider the role of screen printing in today’s commercial sign companies, why it refuses to die, and how to avoid some of the initial frustrations that keep other sign makers from using sign shop screen printing to their business advantage.

WHY BOTHER?
The correct starting point might be to ask why, with all the wonderful digital printing equipment available to sign makers today, would any sign shop want to screen print many of their jobs anyway? There are several answers or partial answers to this question, and we’ll take a quick look at each of them.
First, screen printing, at least manual screen printing, can be added to the types of work a sign company is doing without a large outlay of cash, maybe for as little as a few hundred dollars. This would cover cost of screens, squeegees, stencils and inks. Knife cut direct stencils can be cut on a plotter, and even photo stencils can be exposed with natural sunlight if you know the right method to use. So, low initial setup cost and fast return on investment could be one reason a commercial sign business might want to add screen printing to its methods of doing sign work.

Secondly, there are some types of commercial sign work that just don’t make sense to do any other way, and to keep from turning those jobs down or farming them out, screen printing is still the way to go. These jobs would include multiple prints on corrugated plastic signs, quantity orders of pre-finished metal sign faces (i.e. safety signs, pipeline signs, real estate signs, etc.), and multiples of many types of decals, especially spot color decals.
Thirdly, even though digital printing inks have been greatly improved, the outdoor durability of screen printing inks, when used correctly (i.e., inks that are compatible with substrate, correct stencil and screen mesh size used, etc.) is likely to be much better than digital printing. This is especially important when the signs or decals being printed are safety related and need to last forever (or as long as possible anyway), as in pipeline or utility marking, and warning signs of various kinds.

These pipeline marker decals are printed several to a sheet, and later sheared into individual decals using a guillotine shear. When working with quantities of hundreds, or thousands, the economy of screen printing becomes uncontested.

Also, generally speaking, the cost per impression or printed image for screen printing is typically lower for screen printing than any other type of print, often just a few cents per print. Obviously, averaged into this cost must go the setup time for art, positives, stencils, press setup and so forth. Therefore, the actual cost per print for screen printing goes down as the quantities go up, and the cost per print gets higher when the quantities are small.

WHERE BOTHER?
In our commercial sign business, we use screen printing daily for printing corrugated plastic signs, danger signs, pipeline signs, industrial decals, and most anything that will be done a dozen or more times. Some of our best jobs are repeat orders of corrugated plastic signs, or pre-finished aluminum signs (danger, pipeline marking, and so forth), and decals for vehicles, industry, and pipeline marking. Virtually all of it goes outdoors, and most all of it needs to last as long as possible.
We have printed many thousands of signs and decals by hand, on a shop-made press, and on a semi-automatic “clam-shell” press by M&R. So we have done the work just about every way there is to screen print, though we have not set up yet for UV inks and UV curing.
How hard is it to get into the screen printed sign and decal business for a sign shop that is currently not doing in-house screen printing? Well, I guess that answer depends on who you ask, but it is certainly possible for any sign business of any size to add screen printing to the types of work they do, unless they occupy a retail location that restricts them to having virtually no solvents or inks of any kind in the place.

Screens for sign shop printing can have wood frames, metal frames, or even self-tensioning frames. Screens can be reclaimed and re-used for many different printing jobs.

The items required to begin screen printing in-house would be as basic as a few wooden framed screens, a couple of squeegees, inks and reducers, screen prep and washout supplies, and some hand-made racks for drying printed signs, etc. Or, on a large scale it could mean an automatic press, large screen exposure unit, a darkroom for storing screens, washout tank, roll around drying racks and so forth. Instead of using this article to go into the details of how to set up a shop for screen printing, let’s use the rest of my allotted space in this issue to suggest ways to avoid the up-front frustrations that cause some sign makers to try screen printing and fail, or keep them from moving in this direction to begin with.

NO BOTHER
To start at the beginning, the best possible scenario for a commercial sign business wanting to add in-house screen printing capability is to hire a consultant or someone who can serve as a consultant who has considerable screen printing experience. This is not, of course, always possible, but it may not be impossible either. Even a person from a non-competing field of screen printing, such as textile or T-shirt printing, could be a big help in explaining things like screen mesh, stencil types, film positives and so forth. If no advisor or consultant can be found, availing one’s self of screen print books, seminars, videos and trade articles is a step in the right direction at least.
I hate to mention this, since it seems so obvious, but it is best to learn to crawl a bit before trying to run. This means it is not a great idea to take on a huge and/or multicolor job the first time out, forcing a sink-or-swim situation. Beginners sometimes hate to pass up some grand project and use it to compel them into becoming screen printers, only to end up frustrated, stressed out and losing money as well. So, small jobs first, please.
Also, a beginner will print slowly and will need to keep inks from drying in the mesh, and allow them to work at their pace without problems. This means using retarders or retarding reducers to slow down ink drying time and make printing easier. Warning: some inks are almost meant to be used with automatic equipment and are difficult for even experienced printers to work with. This is especially the case with inks made for vinyls and plastics (like corrugated plastic).

A FEW NECESSITIES
In our shop, we use Nazdar’s 9700 multi-purpose ink for decals (vinyl), and for fluted plastic too (with a 5% addition of NB-80 catalyst for printing on corrugated plastic), and reduce with its retarding thinner. This makes for a very user-friendly formula for many plastic and vinyl substrates (but not metals).
Also, using the largest mesh suitable for the image (and detail thereof) being printed is a good idea. The larger mesh not only puts down a heavier deposit of ink (for durability, fade resistance, and printing light colors on dark substrates), it helps keep the image open while printing. The meshes used in our sign shop, printing on everything from small decals to larger political signs, run from a 125 tpi (threads per inch) to 210 tpi or so. Unless printing with UV inks, a very fine 300 tpi and higher mesh are virtually never used in typical sign shop screen printing.
Another factor or two that can cause drying-in problems is the actual temperature and air flow in the screen printing area of the shop. Obviously, with solvent based inks, there needs to be plenty of ventilation (we have two high volume ventilation fans pulling air away from our screen printer and exhausting it outside) but there can be no direct flow of fan air over the screen itself. Also, the temperature should not exceed 85 degrees or so, which in summertime may require printing in the cooler times of the day if the shop area isn’t air conditioned.
For good quality prints, not only does the stencil used (knife-cut and applied directly to the screen, or film or emulsion photo stencils hardened by light) need to be done correctly and have a clean sharp image, but the screen mesh must be tensioned well and evenly. This can be done by hand by someone with experience, but is best done by professional equipment or with self tensioning screens. A screen that is loose, unevenly stretched and/or warped will not produce good, clean prints.
Also, keeping the correct off-contact spacing when setting up each screen job is very important and simple to accomplish. This means the screen, when in the down or printing position, is spaced just above the substrate and will contact it only where the squeegee is pressing it into contact with the sign or decal being printed. The screen should snap back off the substrate an inch or two back from the squeegee as the squeegee moves across the print.
It is critical that the ink being used is compatible with the substrate being printed on. This seems obvious, but there are landmines out there that should be avoided. For example, most pre-finished metals can be screened with enamel inks with good results. But, metals that have been powder coated may still be pre-finished metals, but they require a different ink since the powder coating is really a urethane heat-cured and hardened material requiring an epoxy or specially formulated ink.
There are several inks that will print on vinyl decal stock, but enamels will not work for vinyl decals and would lead to expensive failures if used to print decals. One serious failure in ink compatibility can cause a beginner sign shop screen printer a considerable amount of frustration to say the least.

CLEANLINESS IS BEST
Finally, keep everything as clean and well maintained as possible. For example, screens can be reclaimed many times, but must be wiped clean of ink residue and as much stain as possible, and stripped completely. We use bio friendly Inkee-Doo by Fran-Mar for the first cleaning (with much wiping), then mineral spirits (more wiping), then dishwashing liquid scrubbed in the screen and rinsed with much clean water. Many good stencil stripping or reclaiming products are available, and most work fine.
But, a good blasting with high pressure water, such as a car wash type sprayer, helps a lot in getting screens really clean and ready to be used over and over. A car wash type high pressure sprayer for home use will cost around $150 and last a year or so. (A commercial duty version will cost 10 times that much, and last five or 10 times longer, so the choice is yours.)
Squeegees too must be kept completely clean, as a bit of left-on red ink (even dried) can put pink stains in the next job being printed with white ink. Squeegee blades (typically 60 or 70 durometer in hardness) must be kept sharp, or sharpened when required even by just rubbing across a long strip of emory cloth stapled to the surface of a work table. This is all common sense of course, but it still takes some diligence to maintain screens and squeegees in the best possible condition, or to toss them when they aren’t up to par.

Generally speaking, screen printing, is not rocket science but an acquired skill like most everything else in the sign making field. For some, this capability adds a lot to the overall success of their company, and helps them service their customers’ varied requirements for sign work. It is not a dead or outdated process. Instead, for those who have the shop setup to allow it, and the willingness to work with the required inks, reducers, stencils and so forth, screen printing still provides a highly practical and profitable means to grow their commercial sign business today, and most likely for decades yet to come.