The Printer’s Trifecta

WELCOME TO EPISODE #26 of Art, Ad, or Alchemy. You can listen to the podcast here as we investigate today’s pressing question — Who knows the game Rock, Paper, Scissors?

Because it occurs in screen printing too! But in our version, the hands represent Ink/Stencil/Exposure. And this being screen printing, we have our own set of rules. Two or three people can play; you just need three hands in. It’s simple.

The fingers facing down represent INK.
The hand flat represents the STENCIL.
The fingers spread represent the EXPOSURE LAMP.
On the third shake, ALL THREE DIFFERENT WINS.

The Screen Printer’s Rock, Paper, Scissors game: The fingers hanging down represent the INK; the flat hand represents the STENCIL; and the fingers spread represents the EXPOSURE LAMP. The idea is that when you play this game, all three must appear to win. 

If anyone is doubled up, it means one of the three wasn’t included in the game and you lose! Put a screen into production without hitting the trifecta and eventually you will have an epic fail. Here’s why:

INK type determines stencil type. Ink can dissolve the wrong stencil. This failure happens on press. It’s imperative to make sure the stencil is designed to work with the ink.

If the STENCIL is bad, it’s usually the light source and process — unless your film is bad. But that’s the art department’s problem to solve. It’s hard to print the ink if it falls apart. Also, stencils are a bit like milk — they have a “best before” date. Make sure it’s fresh. You’ll know the stencil is going bad when washout and reclaim start to take longer and they require longer-than-usual pressure washing. It’s a subtle change.

The EXPOSURE must cure the stencil properly to ensure there is no breakdown when the INK reacts with the STENCIL during printing. The UV LIGHTSOURCE exposes the stencil. But the stencil won’t cure properly unless it matches the light source in output range and time required for complete exposure.

Get one part wrong, everything fails, and the job must be redone. Get them all right, everybody wins, and the job makes it into the press room. Pretty simple.

It’s not a game you want to play, especially in a busy shop. The only way to win is to start at the beginning. First Ink. Then Stencil. Then Exposure. Always TEST to find the BEST.

Your ink must reliably work on the material you are printing. Start there.

1. Printing shirts uses plastisol ink. They also use water-based ink. Paper and plastics can use solvent inks, water-based inks, or UV-cured inks. Industrial applications sometimes use two-part epoxies or other catalyst-activated inks. Textiles use dyes. They also use discharge.
2. Figure out what ink(s) you are running. The main consideration with ink is does it stick and wear well on the substrate? Secondary considerations include:
   1. Can you dry or cure it with your current production equipment?
   2. Is it easily available, along with modifiers and additives?
   3. Does it print smoothly and perform well on press?
   4. Finally, cost. In many cases, ink is one of the smallest components that make up the cost of a job. Cheaping out on ink is false economy.
   5. The second step is to find a stencil system that is recommended to be resistant to the ink you’ve chosen. (Water-based, solvent-based, discharge, or specialty ink, etc.).
3.  Each stencil manufacturer will have a range of emulsions with different properties and resistance to different inks, and your local supplier may not stock them all. At the risk of repeating myself, don’t buy cheap emulsion. The cost of one failed screen in production is much more than the cost difference for a container of the most expensive emulsions.
4.  Into this, you must factor in the solids content and the ability to develop and hold fine detail. Some stencils give much finer resolution than others. Some people don’t need this. Some do.
Other things to consider are:
   1. The speed of processing. Super-fast emulsions require safelight conditions to prevent pre-exposure.
   2. The longevity on press. Printers running long production runs want a stencil that won’t break down in production. This may involve hardeners and make a knife your reclaiming process.
5. People using CTS systems or automated coating may need something special.

That leaves us with exposure and the light source. Your system must fully cure the emulsion so it can be processed and then used in production and resist the ink. The light source also must create a sharp, defined stencil image.

Other considerations include your shop’s volume. Maybe you are so busy, you need to jump to CTS. Recalibrate from film processing. If you don’t use a vacuum and put the screen under glass, your exposure times will be different. Faster. Test to be sure.

The thing to remember as we race to faster and faster exposing and devolve from point light to tubes to LEDs is that all light sources are not created equal. They vary in output, and are measured in nanometers. The newer LED systems have narrow output, where the old metal halide bulbs had a broader spectrum.

Certain emulsions won’t completely cure if they don’t get the broad exposure. And, under high production, will fail prematurely.

In the screen-printer’s version of Rock, Paper, Scissors, one hand does not beat another. In our version, INK, STENCIL, and EXPOSURE all must work together to win. Because if they don’t and you miss one, the game is over. You lose.

Part of the reason I like to refer to alchemy when we talk screen printing is because it involves a lot of science — physics, math, material sciences, a lot of conversions from liquids to solids, light spectrums, photo-initiated processes…the list goes on. But it’s practiced mostly by non-credentialed individuals, outside of labs, in uncontrolled environments.

Like old time alchemists, we screen printers turn raw materials such as inks, stencils, and substrates into gold. They are well-saleable objects, which can be converted to cash and that could get you gold. The whole is worth a lot more than just the sum of its parts. I like to use Warhol’s Marilyn Monroe prints as an example … a shitty screen print by today’s standards on $4 worth of paper, a bit of ink, a bit of labor, a signature … and it’s worth $193 million. But that conversion into a valuable object is still there.

Here’s the kicker. You can’t make bank if your process doesn’t work on the regular. But you can eliminate a lot of production problems and premature failure if you just learn to play the screen printer’s version of Rock, Paper, Scissors.

I hope you enjoyed this episode and it helps to make you better alchemists working in your screen-printing labs. If you want to learn more about stencils and exposing, I’m going to refer you to Episode 9 “Stencil Science” with Dave Dennings from KIWO. The company also has a lot of info on its site. In full disclosure, I use Murakami in the studio, because it works for us with our inks and light source. But I also use Saati, Chromaline, and yes, Kiwo, depending on where I’m working and what we are working on.

A poster or a hydrogen fuel cell or some weird paste filling holes on a circuit board require different components. Ink plus stencil plus proper exposure all work together to do the best job. Want more info on ink testing? Watch Corey Mathis in Episode 24 where he outlines how the team at Nazdar technical services tests ink compatibility on products.

That’s a wrap. Apologies for no guest, on the podcast but I’m holed up in Mexico without proper Internet and phone access. After that, I had a great time in Austin at SXSW again this year, where we were demo-ing at the Flatstock exhibition. finally, a shout-out to my team at SmartWork Media for making it all happen, my editor Marcia at Sceen Printing magazine for encouragement, and you the listeners and fellow screen printers who keep this crazy industry moving forward. This is Andy MacDougall for Art, Ad, or Alchemy.