The Variety of Digital Inks That Are Available (Podcast)

There are many different types of digital printing ink available, each best suited to different substrates and printing methods. Here’s what you should know about the varieties of inkjet and pad printing inks that are available today.

John Maher: Hi, I’m John Maher, and I’m here today with Gregg Harwood, digital product manager at Inkcups, a leading supplier and manufacturer of industrial inkjet printing equipment, pad printing equipment, inks, and accessories. Today we’re talking about the variety of digital inks that are available. Welcome, Gregg.

Gregg Harwood: Thank you.

The Importance of Specific Digital Ink for Specific Substrates

John: So Gregg, why do you need specialized ink for specific substrates?

Gregg: Inks vary depending on the substrate, like you say. The substrate is going to carry a certain surface tension, and then your ink will carry another surface tension. If the surface tensions don’t align, then what you’ll get is poor adhesion or the ink to actually repel off the surface.

So the surface tension of your ink must be under the surface tension of your substrate or else, like I said, you’re going to get that kind of beading up or that water effect where it’s not going to want to bond onto the product.

John: Okay. Then it could easily peel off or scratch off or that kind of thing.

Gregg: Yeah, or just not stick at all. We use a UV ink, so when the UV does cure it, it will somewhat pin it perhaps. But then it easily, like you say, will flake off. You really need to anchor into the substrate. The first color to anchor in is typically white. If you’re not getting that to anchor or to bond, then your ink’s essentially floating on the top layer, and it never really sticks. So understanding surface tension or dying levels is critical.

The team here, we have a team of around four application specialists that understand it well. We’ve worked hard to elevate that skill in understanding that, and we perform for any sort of sample request or adhesion test request, we’re performing that in our lab here.

Which UV Inks Go with Which Substrates?

John: Okay. So can you give me an example of a certain type of substrate and then the type of ink that’s necessary to adhere to that type of material?

Gregg: Sure. We have some versatile inks. Because when you choose an ink, typically a customer’s not going to buy a machine for one product. They want to buy a machine for multiple products. So it’s important to have a versatile ink. With that being said, different substrates may require different pre-treatments in order to run with one single ink. Because the machines aren’t really designed to pour different ink in for a different substrate and constantly have this rotating ink. It’s more designed to have one ink and then have different pretreatment methods in order to make that ink work.

But in the case of, you know, a company might print Tritan, which is a kind of a copolymer plastic that’s manufactured. They may do that, and that might be 80% of their business. Well, because of that, and because Tritan is a pretty popular product, we developed an ink that can print on Tritan without any pretreatment.

So now the company might have 80% of their business where they don’t have to worry about anything. They just print right on it. Ink sticks great, and they’re good. The other 20% might be on something else, like glass or metal or whatever. Our job would be, okay, Tritan we got covered, now let’s figure out what pretreatment you need in order to make the same ink stick on the other items. We’ve been pretty good at that.

Different Types of Ink Pretreatments

John: What types of pre-treatments are you talking about? Is it a different type of material that has to be put onto that substrate before you print on it? Or is it a type of washing that you do? What does that pretreatment look like?

Gregg: Sometimes pretreatment is a flame process where you’re using the plasma of a flame to change the surface tension. Sometimes it’s a white bond chemical primer, where an operator literally wipes it on with a lint-free cloth before they print it. Sometimes it’s a combination of the two.

Additional pre-treatments are a corona treatment. It’s less of a flame, it’s more of an electrical type of charge to the surface. Plasma being the same, but a little bit more powerful. Then we’ve also developed a sprayable primer for glassware, which is in combination with a flame. So you’re actually heating the product and then spraying it with a primer. So there’s a lot of ways to get the substrate pretreated. Obviously, the less touches, the better. The least amount of work upfront, the better.

Then when it comes to post-treatment, we don’t really need it much. You can usually get what you need prior to the print. That way right off the machine, you can pack and ship.

Digital Printing Ink Varieties

John: Okay. So what types of varieties of ink are there out there, and especially in terms of the different types of substrates that you’re printing on?

Gregg: For digital, I mean, you could probably group it. There’s a lot of inks. But you could probably group it into three buckets, water-based, solvent-based, and then UV. We utilize a UV LED curing ink. We don’t get into the solvent-based or water-based much. Primarily, again, UV.

Then within UV, there’s different characteristics of inks, like the Tritan ink, for instance, is specifically for Tritan. It can work for other things, but it’s designed for Tritan. We have other inks in-house that are designed for the sport bottle market. [It has] squeezable, crease resistance. You can actually bend it, and it doesn’t crack. Where if you’re going so much on that side, it doesn’t crack, but now it might be a little bit too flexible to work on a real rigid product.

So it’s finding that happy balance. It’s really understanding what the customer’s product line is and where their main volume is when picking these inks.

John: Like you said, if they’re doing 80% of their printing on the Tritan, then that makes sense to have that be the main ink and then find ways to utilize that ink for other products.

Gregg: Right, with the common understanding that we’re trying to minimize how many machines they have to buy. But sometimes, it’s just the honest discussion and having the expertise to say, “All right, we looked at your products, here are your top 10 products. We can handle eight of them with this ink.” Does that justify the machine? In most cases, it does. Then they can consider a second machine at some point for the other SKUs, maybe different ink series.

Challenges of Printing on Metal Substrates

John: Okay. What about printing on metal? Is there a specific ink or ink series that’s used for printing on metal products?

Gregg: Yeah, metal is interesting. Stainless, we have a really good solution. We have 60, 70 machines out there running on stainless and with strong success, where it’s abrasion-resistant, has very strong dishwasher safety, and the FDA approved it. We have that kind of locked down.

When you get into some coated metals, it becomes a little bit tricky, because you don’t know where these coatings are being made. So you might get a powder coat that’s made in the U.S, and it might be as consistent as it can be. And you find that solution once, and you’re good. Then when you’re dealing with overseas and these coatings are made out of who knows what, a lot of testing needs to be done.

You may get a batch of product, it may be great, you might have the right solution. Then three months later, you get the same product from the same supplier, and their coating changed. Now you’re having adhesion issues. Now you got to go back to square one and figure out what pretreatment is going to work.

So when you’re dealing with that sort of variable, having the knowledge of, I guess us telling our customers like, “Watch out for this. This is common,” is the best we can do. But I don’t think anybody else would warn their customers that this is something you need to watch out for. They don’t know enough to do that.

John: Right. And at least you’re, like you said, you’re giving them that warning so that they know if all of a sudden they’re starting to have some problems printing on a certain product, they think back to what you said and they go, “Oh, let’s look and see whether or not the coating on this changed from our manufacturer,” or something like that.

Gregg: Yeah. All of our techs know this. They’re all educated. They all know this. So when a customer does contact us, and it’s typically through our support line, they say, “I can’t get ink to stick to this.” It’s, “I got a return from a customer,” or whatever it might be.

One of the first few questions, I mean, part of our script when it comes to adhesion is, “Have you ever printed this before? Did you have success? Has your supplier changed? Do you have the material makeup of the coating?” And many times, we can look right at the material makeup of the coating and say, “Ah, has Teflon in it. Has this in it.” They can then go back to their supplier and change it, rather than going down a rabbit hole on the service side, and we may never solve the problem if we don’t know that something’s changed on the supplier end.

John: Right, because you could be thinking it’s something wrong with the equipment itself or something like that or the ink. So you try to narrow it down to what the issue is.

Gregg: Exactly.

How to Decide on the Right Ink for Your Product

John: So how do I know what type of ink will work best for my product? Do you work with your customers to try to figure that out?

Gregg: Yeah. So when a customer buys a machine from us, they typically will have their top three or four SKUs or substrates, and we’ll do that initial type of ink validation, and we’ll choose the right ink. Then beyond that, we work as a consultant. They come across products, we provide them some sample primers, where we give them the knowledge and the process of how to test different substrates.

So when you get a new product in, here’s what you do. You do this and then you primer wipe, and you can test all the primers you have there. And then if something works, you buy it in larger bulk.

If they are stumped or if they don’t have the time or they don’t want to do that, then they can send the product into us, we’ll get it into our sample queue, and we’ll get it tested in our lab. With that, we’ll provide them a report back. We’ll provide them a quote for the primer, and pretty much we’ll do that legwork for them as well.

John: All right, well that’s really great information, Gregg. Thanks again for speaking with me today.

Gregg: No problem, thanks.

John: For more information about Inkcups and Inkcups’ printing equipment, visit the website at inkcups.com or call (978) 646-8980.