How Your T-shirts Get Printed: Inks and Chemicals

This is number four in the series. If you missed the first three, you can start here: How Your T-shirts Get Printed: The Basics.

If you want to skip the other lessons for now and just learn about inks and chemicals in screen printing, you’ll do just fine. But later, when you’re wondering about apparel brands, fabric, and artwork, it will behoove you to go back and read those posts.

Now quick, before I say “behoove” again, learn about how to choose the right ink for your printed apparel!

Ink and Chemicals: A Necessity

Well, you can’t print a shirt without ink. Okay, technically you can use coffee, or a nice marinara, maybe some red wine. But to get professional, consistent results that you can sell in a retail market, ink will be needed. Some sort of chemicals will also be a requirement. In screen printing, various chemicals are used to make screens and clean ink off of the screens and equipment.

I know, we all want to live in a world where everything we buy involves using only air and water. It does limit our experience a bit. For example, you would not be reading this right now without plastics and chemicals. Your yoga pants? Plastics! As much as we all want the Earth to be a safe place to live for future generations, there are some compromises that we all make. You can choose to not produce apparel. We can choose not to print any. Since those two things are happening anyway, we may as well make sure they happen in ways that least affect the land, water and other beings who live here with us. End of speech! Let’s break it all down.

Chemicals Don’t Kill People, People Kill People

Let’s get the big scary chemical thing out of the way first. Way back in the early days of screen printing, the chemicals that were used were highly toxic. Some printers even wore masks, which tells you something. The ones that didn’t wear masks probably got cancer. But they likely smoked cigarettes and ate buffalo jerky so we’ll never really know, will we?

Today, the chemicals we use to clean our screens are nowhere near as toxic. In fact, most of them are soy-based. That doesn’t mean I would put it on my cereal. We still need to be cautious with our cleaning products, but limited exposure will not cause us to die. Very important.

None of the chemicals we use in our shop are tested on animals or contain animal products. That’s really important to us. If it’s important to you, you should ask your printer about that. Here’s a juicy tip: If they truly care, they will be all over that answer like sriracha on a taco. If they don’t actually care, they’ll say something like, “Uh, I think so. Sure, yeah, whatever.” Learn to spot the difference!

Very simply, screens for printing are made using a photo emulsion. A liquid is coated onto the mesh screen and dries. A screen can be used for 1,000s of prints. Once the screen has lived its purposeful life, the emulsion is removed using a chemical (see above) and water.

Most chemicals in screen printing don’t end up on your apparel. One difference is a sticky spray that keeps the garment laying flat on the platen during a print run. Now, this spray will disappear after the first wash. You don’t really feel it, but it’s there. There’s another version that is a liquid and not sprayed, so it saves the ozone from HFCS. It also saves our lungs when we print. A rad bonus.

There is one chemical that we never use in our shop and I’ll explain that in detail later, as it has to do with a certain style of printing.

Think About Ink

There are two kinds of ink used in screen printing: plastisol and water-based.

Plastisol ink is, you can probably guess, made using plasticizers and pigment. They tend to be thick and when printed on a garment, typically have a strong hand feel, also kinda stretchy. Plastisol is cured (dried) using heat.

Water-based ink, no surprise, is made using water, solvents and pigments. The solvents bind the pigment to the water until it’s dried. On apparel, the ink is cured using heat and moving air. The water evaporates, leaving behind the pigment and some solvent. It has almost no hand feel on the garment.

People sometimes assume that water-based ink automatically earth-friendly. It definitely sounds friendly, like we could drink a tall, cold glass of screen printing ink and not die a grisly, painful death. Or, we could just wash it all down the sink with the moldy salsa. The problem is that water-based ink is not just water. There are pigments, binders, thickeners, and sometimes, even co-solvents in the ink residue.

So even though it sounds enviro-friendly, water-based ink can still be toxic and not good for municipal sewage systems – or the oceans and rivers where the water eventually winds up.

In our shop, the plastisols we use are PVC-based, Phthalide-free inks that, when cured with heat, turn to a solid. We clean our screens with a soy-based cleaner and cotton rags. The cleaner reacts with the ink, rendering it biodegradable and drain-safe (can be filtered in our municipal system). The cotton rags are heat cured, making the plastisol a solid, which can be disposed of – except that we reuse our rags so they have a very long life.

It’s not a death match between water-based and plastisol. There are good reasons for using both, depending on the situation. For example, we need to use plastisol ink to print on spandex or triblends. We always print posters with water-based ink (you can’t heat cure paper).

Plastisol inks are also great for achieving bright, vibrant prints on dark garments. Water-based inks typically have a more faded, vintage look.

The bad, bad Leroy Brown chemical I mentioned earlier? It’s called discharge ink. It’s used in a method where you print water-based inks on dark garments. The discharge ink actually removes the dye from the shirt, allowing the colored ink to appear more vibrant. Sounds like a lovely solution, yet the discharge method is highly toxic. The discharge ink itself is toxic, the printer needs to be very cautious around it (wear a mask if you don’t want cancer or lung damage). Also, the dye in the shirt has to go somewhere, and that’s into the air as well. And if you were thinking, who gives a crap about the printer, gimme mah shirts!, sometimes those materials leave residue on the garments that can cause skin problems in sensitive people – even after washing. So there’s your customer to be concerned about.

There are some new and wonderful water-based inks appearing on the market these days that print brighter than the olden days. That would be our choice.

So What’s the Right Ink for Your Apparel?

This is a lot of info to take in, I know. There’s actually much more, and it takes years of experience printing with these products to really understand their effectiveness. So the best way to know what ink is the best to use on your tees is to consult with a professional screen printer. They should guide you in matching up the best inks with your design and fabric.

As always, you can ask me any questions in the comments below or get in touch directly!

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