Silicone Pad Printing Challenges
Q: Of course. So, what are the particular challenges of printing with silicone inks?
A: The challenge here is that we have a lot of pad printers, and a lot of screen printers that use solvent-based inks. Silicone ink is a whole different animal. It cannot dry the air. This is a heat cure system only. It's designed to do one thing and one thing, stick to silicone. There's a whole bunch of other tidbits we can get into that will help any pad printer decorate promotional products that are made of silicone.
Q: Ok, so first of all, how do I know my product is actually silicone? Since there are some other materials that might be stretchy, like plastic, I might think of silicones, but they're not.
answer. So here are some different tests, internal tests. You are right that there are some materials that have a silicone feel to them. There are a lot of TPU and TPE, or thermoplastic elastomers as they call them, that feel like silicone. So the essential difference between the two, silicone itself doesn't deform at 600 degrees Fahrenheit. It actually holds heat. Another feature of silicone is that it is not flammable. So we can do some tests in the lab. If we get a few pieces from a customer that says "Let's try your silicone ink." We can do what's called a burn test. We can put it on a small fire and see if it burns or keeps burning. Silicone will go out automatically. Also leaves a white ash.
Q: You take it away from the flame and it goes out? It doesn't catch fire?
Answer: Correct. Another thing silicone won't melt unless it's over 600 degrees.
Q: Is that why you see it so often in cooking utensils and things like that?
Answer: Correct. It conducts heat very, very well. Thermoplastic elastomers decompose almost instantaneously. So you know our silicone inks are not a good solution, we need to talk about something different.
Silicone Resin Pad Printing Ink
Q: Why does the silicone resin ink only adhere to the ink?
A: This is a good question. So silicone, the inherent property of silicone is that it wants to repel anything it touches. It releases anything. What sticks to the silicone alone is the silicone. So if you take a wet silicone, dry it out, and then take a wet silicone and dry it on top, the two basically fuse together and become one. Again, what we're really dealing with, we're not really dealing with silicone ink. We're really just dealing with liquid silicone, and once it's heat cured, it becomes a permanent part of your product. To be honest, we have some customers who sometimes make typos. Their next question to me was "how can I take it off?" Ultimately you can't. It actually melds on itself. This is not the case with solvent-based inks. Basically-
Q: You can wipe it down with solvent and start over.
Answer: Correct. With most of them you can. right. So again, silicone sticks to silicone, and that's the only thing that sticks to silicone.
Q: This is interesting because I thought the name silicone ink meant ink glued to silicone. It's actually made of silicone.
Answer: Correct. certainly. Yes. All the properties and chemical composition of the ink are basically silicone.
Silicone pad printing process
Q: So, what is involved in the process of printing with silicone inks?
Answer: OK. So here are some tidbits we can talk about. So one of the things we mentioned before is that we're not dealing with solvent based ink systems. So a lot of our flatbed and screen printers are used to dealing with air dry ink systems. Some things you need to get tired of with silicone, it doesn't air dry. It stays wet until you heat it. So it's a heat cure system. So one of the difficulties with silicone printing is having multiple colors. Hardly anyone does multiple colors with silicone because the problem is you print one color, you need heat to cure it, you need to take it back, and print another color on top of it. This is the first thing you should consider. The second thing you should consider is that when you use silicone inks on plates, in a typical solvent based system there is residual ink on the plate itself that will air dry and not be absorbed by the plate . Silicone ink, that is, residual ink, may be picked up by the silicone pad and deposited on the part. While there are a few things we would like to tell our customers to be "if you are going to choose a pad to do your work on, choose one that is as close to the size of the image as possible so you don't catch any insulating ink left on the edge of the mug." This Very important. The second thing, we always tell our customers, it's a heat cure system. I don't know how many times I've gotten calls from customers telling me the ink won't dry. The technical data sheet we developed clearly shows that the ink takes a good 4 to 6 minutes to cure between 200-225 degrees Fahrenheit. Because these people are used to letting their products air dry within minutes. That case is not made with silicone ink. It is always heat cured.
Q: At a specific temperature, what is the temperature range for the cure?
A: So the temperature range is, it all depends on how much ink you put. But in the temperature range of 200-225 degrees Fahrenheit or higher for 4 to 6 minutes. Again, this depends on the size of the picture and the amount of ink used. One of the things we found out recently is that the thickness or thickness of the product you are decorating should also take into account how long you need to heat it. A thinner piece of silicone retains heat and heats up much faster than a thicker piece of silicone. Therefore, thicker silicone and thicker silicone items may require a longer time in the oven.
Q: OK, OK. How did you know for sure? Is it just a matter of testing?
Answer: Yes. real. So we give it a range. Honestly, the customer should do their due diligence, and depending on how hot the dryer can get, they can get away with it in 4 minutes or less. Unfortunately, some other customers are only capable of lower temperatures and require a longer time in the oven or dryer.
Q: Yes. So you said earlier that silicone is something that sticks to silicone alone. So I guess that means silicone ink is a separate option, printing on silicone, or are there other options?
Answer: Correct. As far as I know in the industry, silicone ink is something that sticks to silicone alone. I've seen some videos in CHINA where people pretend to do digital printing with silicone products. I'm not too sure if it has something to do with the primer, or what they did to the ink.
Liner Selection for Silicone Inks
Q: Yes. A word on liner options for silicone inks. Again, we do pad printing on silicone. So, are there certain types, shapes, or styles of pads that can be used with silicone inks, and only those types?
A: This is a good question. We were a little moved. So the shape of the mat is always determined by the parts, first and foremost. So one of the things we need to think about is we have a silicone pad, we have silicone ink. The two want to attract each other, but we want to apply the ink from the silicone pad to your silicone part. So one of the things, like I said before, one of the things we try to tell our customers is "try to pick a mat that's about the same size as your picture." That'll help-
Q: You don't get residual ink on the outside.
Answer: Correct. The second thing you need to know is that at the end of the day, every 10 or 15 prints, you're going to need to wipe off the silicone pad because you'll have silicone ink build up on that piece that didn't transfer to the silicone part. Because they want to cuddle with each other again. This is not difficult for many printers to adapt to because it is a solvent-based ink. Ink has come off the plate completely. This isn't necessarily the case with silicone ink, as it either wants to stick to the pad or to your part. So you'll always have residual ink left on the pad, which will eventually be wiped off.
Q: Is this because the pads are also made of silicone?
Answer: Correct. they are. All printing plates are made of silicone. One thing we should mention is that silicone ink is a platinum based silicone. So there are two types of silicones, platinum-based and tin-based. Platinum based is a silicone that requires heat curing. Tin-based silicone is a silicone that can be air-dried. The industrial inks I know now are all platinum-based silicones that require heat curing. Some pads can be tin-based and others platinum-based. Most of what we do here are platinum-based silicone mats. So they are basically the same material. So they want to be attached to each other.
Q: Talk more about multi-color. You mentioned earlier that this could be a problem because obviously if it doesn't air dry then you can't just print one wet color on top of another wet color or they will mix together and mess up. So you print one thing, you heat cure it, then take it back and print a second color on top of it. How many times can you do this? Having problems with multiple colors?
A: So the problem of multi-color, most of our customers are now monochrome silicone pad printing. The product where this particular ink became popular in the industry a few years ago was a silicone wallet on the back of a cell phone. I think everyone knows what that looks like by now. These are mostly screen printed or pad printed in one colour. Now, if you're going to do color pad printing with silicone, one of the things you need to think about is registration. So if you have a two-color or three-color job that is closely registered to each other, you're going to have a really hard time printing one color, curing it, then coming back and trying to register the second color where it needs to be.
Q: By registering you mean lining it up so it's on top?
Answer: Correct. Some of the graphics I've seen work successfully are when you don't have such a tight registration, and there's a gap between two colors where the second color's position isn't that important, then it's a lot easier. To be honest, I haven't seen many clients who have done more than two colors. The two colorful artworks I've seen, are very, very loose. Normally, the colors don't touch each other.
Q: Is a distance of a few millimeters really impossible?
Answer: Correct. No one will catch it.
Solvent Inks and Silicones
Q: Talk about the difference between solvent-based inks and silicones, and how they affect the printing process. Plate repair is another thing we discussed.
Answer: Of course. So solvent-based inks, they're made from solvents, and the solvents evaporate very quickly. The cup turns back and forth. If there is any secondary ink on the outside, usually when the pad comes down to take the image, the secondary ink on the edge is pretty dry by that time, and it won't be picked up by the pad. Working this way is easy. Among the silicone inks, some printing plate materials are photosensitive polymer plates that do not cooperate with silicone inks. These are the panels that basically need to be exposed. Some of the better results we've seen are some laser plate materials where we're actually etching the graphics on the plate. Those docs are really, really clean, so there's not much secondary ink left on the side. Here's one piece of advice I can give our listeners. If you choose a flat material, a better choice may be laser etched rather than photopolymer etched. Photopolymers can't be that clean. This isn't much of an issue when you're using solvent-based inks. This is a huge consideration when you use silicone ink. Because sometimes you can't find a "clean doctor" and your pad will want to collect all the excess ink. Of course, unfortunately, this affects you.
Q: OK. Any final thoughts when it comes to printing with silicone?
A: Remember that you are not using a solvent based ink system. This is a heat cure ink system. Honestly, a nice part of this is that you have a 24+ hour partial life. Solvent-based inks are usually one-day or eight-hour shifts. Be mindful of the size of the pad you choose, and be mindful of your plate material. You should try to make it a laser board, not very successful.
