Technical Support Blog

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Real Talk: Curing Ink

If you are a screen printer, curing your plastisol ink is the most important thing you are going to do today. We manufacture ink. We make this stuff. It’s messy. Really. Come to Louisville and check it out. This is happening. Having said this, how is it possible that we are not the first phone call when it comes to learning how to testing dryer temperature? Oh, you called the dryer manufacturer? Bad idea. These guys are more interested in how many prints an hour their dryer can produce. Their testing methods are clearly biased towards a fast dryer belt speed and higher temperature. This makes them look good when you are producing 800 or 1000 prints an hour (I picture an equipment salesperson flexing his muscles as he brags of production capabilities). Hey, we like some of these guys but this is how they sell equipment. Fast and hot is not a curing strategy we can get behind. Too much can go wrong.

Again, we manufacture ink. Our motivation is to keep the ink on your fabric. Vibrant prints. Consistent prints. No fabric damage. Our motivation of keeping our ink looking good should tell you that listening to us about curing will keep YOUR best interest in mind. We don’t want our ink washing out. Under/over curing can lead to dye migration. We don’t want that either. We want you making fantastic prints you can post to our Facebook page with a smiley face emoji or a thumbs up.

Let’s get into it. How are you testing your dryer? Whatever you do, don’t say the thermostat on the dryer. This is an important number but not for judging the ink temperature. Are you using Thermolabels (paper thermometer), heat probe, infrared gun, something else, or nothing at all? Scratch the something else and nothing at all from your wish list. Nope. Can’t do that. How about the infrared gun? This is a sticky situation and I can already feel the eye roll coming. You can’t use this to measure ink curing. You can’t. I know you want to. I know it’s convenient. You can’t. The infrared gun will only measure the surface temperature of the ink. When an ink is not cured, it is always where the fabric meets the ink. This part of the ink deposit is still “gummy” for lack of a better word. It is not fully fused. It isn’t cured at the bottom. The infrared gun can’t see this. I was once told this was similar to a PC vs. Mac conversation. I was against the gun out of my own snotty preference. Nope. I was against the gun out of necessity. It can’t help you unless you are looking for hot/cold spots on a heat press or checking a dryer element to see if it is working. I am not questioning its accuracy, only its ability to measure where it matters. Moving on. The heat probe is accurate only when the cross wires are placed in the ink. This creates a few problems. First, it ruins the print. Those wire marks aren’t coming out. Second, it can be hard with thin ink deposits to keep the wires in the ink. Finally, it is known to be inaccurate when testing dryers without forced air. Most electric dryers do not have forced air.

This conversation just lead us to Thermolabels. These paper thermometers are not perfect. However, they are the best option to ensure your ink is cured properly. This is reality. This beautiful, low tech device has been saving screen printers from bad decisions for years. The #5 package measures from 290ºF to 330ºF. This is perfect for regular plastisol ink which is most often cured at 320ºF. The #4 package is available for our low temperature inks measuring from 240ºF to 280ºF. Side note: if you aren’t using our low temperature inks…you want to. Call me.

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So, how do you use these wonderful little devices? First, my suggestion is always to test each and every fabric you are going to print when you are going to print them. Place a Thermolabel next to the first and last print of the order. Take these Thermolabels and attach them to the work order. This is accountability at its finest. This will save you thousands of dollars and prevent angry customers. Just do it. OK, this is important…make sure when you are attaching the Thermolabel to the fabric, you push it down firmly. Rub it if you have to. Thermolabels often get a bad name when the 310ºF indicator has not turned black but 320ºF indicator has. This is why I like to attach it when it is still on the platen. This gives you a hard, flat surface to work with. The 310ºF indicator didn’t turn black as it was not fully attached to the fabric. It’s not a bad label, it simply did not get the opportunity to read accurately. Another important note, the temperature has not been reached until the entire 320ºF square is black. Black around the edges is meaningless, please disregard these.

Now that you know how we test for ink curing, you need to know how to set up your conveyor dryer. Gas dryers are the most consistent. This is always our preference as electric dryers are prone to hot/cold spots. This can really be a drag, especially when you are running a fast belt speed. Regardless of your dryer type, they will be set up the same way. Let’s get your belt speed correct. Don’t worry about the temperature yet. Get a hold of a stop watch or a smart phone with a timer. Place something on the belt and start timing the moment it enters the chamber and stop the moment it exits. The size of your dryer combined with your production requirements will largely determine your belt speed. We would like to see the print in the heating chamber for a minute if you have a short dryer belt. A minute and a half is ideal for a longer dryer belt. We know many printers with smaller dryers don’t want to hear this but it really is the way it should be. However, if you simply cannot do this, please keep the print in the dryer for an absolute minimum of 30 seconds. This is risky as ink curing is a time and temperature event. Thanks to the inconsistent nature of electric dryers, if there is temperature fluctuation, there is no chance the ink will be cured. Very small margin of error.

Now that you have the belt speed set up, you need a temperature. I really can’t tell you what temperature your dryer needs to be. So many factors! I can tell you a few things I have seen. Gas dryers are often in the 350ºF to 375ºF range. Electric dryers could be anywhere. 400ºF…800ºF…1100ºF…I have no idea. It depends. This is why Thermolabels. You need them. Get yourself a starting point, let the dryer heat up, and test with a Thermolabel attached to a cotton shirt. Important note, we are sticking with cotton for the moment. You don’t need a printed shirt, only a shirt and Thermolabel. Also, don’t change shirt colors. Don’t change shirt sizes. Keep it consistent. This matters, especially with electric dryers.

Do you have it now? I am looking for a slow belt speed, a cotton t-shirt with zero heat-related damage, and a Thermolabel with 320ºF indicator that is completely black. If so, you aren’t finished. Grab a thick cotton hoodie. Attach your Thermolabel. Place it on the belt. Now you may be upset. Those of you with a gas dryer and a long dwell time in the heating chamber probably feel pretty good. Those of you with an electric dryer hate me. It’s not my fault. Be nice. The Thermolabel is indicating a far lower temperature. This is reality. Yes, the hoodie was heavier than the cotton t-shirt. This means it takes longer to heat up. This is why you will be attaching a Thermolabel to each and every order. First and last print. You can predict some of these temperature fluctuations but not all. A thin 100% polyester tee will go the opposite direction. You will heat up quicker and possibly damage the fabric. Again, printing with our low temperature inks yet? Call me. What you will want to do now is slightly slow the belt speed for the heavy cotton hoodie. Slightly speed up the dryer belt for the thin polyester tee. I said slightly. Remember the time minimums I discussed earlier? Try to stay above these.

OK, you now have a road map for curing ink properly. You have Thermolabels. You have accountability on every order you will print. Now for the fun part! I get to tell you what is going to happen if you don’t listen to me. Predicting the future is my favorite!

  • Fast dryer belt speed:  You are begging for a problem. A faster dryer belt means you need a hotter chamber temperature. So many problems. Think about this…the faster the belt is moving, the quicker the print will either drop into a box or be stacked onto a table. In both situations you have ink risks. The ink is really hot with no cool down time. It may stick to itself or another print. Ruined! Also, if plastisol ink heats up too quickly it can get bubbles or little holes in the ink. This looks terrible. Add fabric problems such as ghosting, shrinking, scorching, fabric discoloration, and melting to the already fatal ink problems, just don’t do it. Have you heard of our low temperature inks? Call me.
  • Using an infrared gun:  Your ink is under-cured. That’s the deal. Promise. Your gun measures 320ºF. Your Thermolabel is not turning black. None of the indicators are black. Does this mean the Thermolabel is broken? Expired? They never worked? Nope. 320ºF is the surface temperature. That is all. For those who want to make the argument that they can use the infrared gun to measure the surface temperature of the ink to the same surface temperature of the ink when a Thermolabel was indicating 320ºF…how thick is that ink? What color is that ink? Just don’t.
  • Using a heat probe:  This is not a horrible option but you are left with lines in your print and calibrating every year. Time consuming. Messy. I love me some Thermolabels.
  • Not testing your dryer at all:  Why did you even read this? You are living on the edge.
  • Using Thermolabels…but not often:  Your dryer may look like your most trustworthy friend, but it is not. This is your dryer. Test it. Each fabric heats up differently. Test it.

Hopefully after reading this you are timing your dryer belt speed, adjusting temperature, and including accountability into your process. If you have any questions or problems, be sure to call me at 800-942-4447.


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What is ghosting?

Screen printers struggle to prevent a problem known as ghosting. It simply is very difficult to predict exactly when the problem will occur. Luckily, we have tested enough fabric to know what causes ghosting and how to prevent it. If you give us the chance, we will stop ghosting problems from affecting your production.

What is ghosting? See the picture above. What is that exactly? Ghosting is a term we coined as we had to call it something. Perhaps reverse dye sublimation would be a better name. Dye sublimation is the process of dying polyester fabric. Ghosting is basically the reverse process as some of the dye is leaving the fabric. This is why you may be left with some strange colors. For instance, a navy tee which ghosts may look magenta as the blue has disappeared. The magenta dye was not harmed during the screen printing process so magenta is what you see. Sounds simple, right?

“Why can’t you invent an ink which stops ghosting?” This is a question I hear often.  We already have created an ink (a few actually) to prevent ghosting, but it is not as simple as that. Ghosting has more than one cause. I will explain. Physical ghosting is caused by heat. You may have seen this when decorating a light color of polyester. If the tee is not layed flat on the dryer belt, the folds of the fabric which are closer to the heating element may change color. The heat alone is ghosting the fabric. Screen printers who decorate apparel know there is no way to take heat out of the process. You can certainly limit the heat as I will discuss later in the article. You simply cannot remove it from the process.  Ink needs to flash cure. Ink needs to fully cure. Heat is going to happen.

Chemical ghosting is when the ink formula itself is causing the ghosting. Keep in mind chemical ghosting is most often found when screen printing white ink. Ghosting is not a problem exclusive to white ink but it is far more common in white ink due to a variety of necessary additives. These additives may help white ink cover better on dark fabric, print easier through fine mesh, or prevent dye migration on polyester and polyester blend fabrics. Even a simple black ink is capable of ghosting fabric.

Now that you know what causes ghosting, there is just a little bit more to know. Your ghosting troubles can be a combination of physical and chemical ghosting. One common occurance of this happens while hot stacking. Hot stacking is exactly what it sounds like.  You snatch a garment off the dryer belt and place it on a table. You snatch the next garment and place it directly on top of the previous garment. Both of these garments are hot. The ink is hot. If you are printing the wrong fabric with the wrong ink, you may have a ghost image on the back of every garment. Heat in addition to ink formulation is the most likely ghosting culprit.

OK, give me the magic fix already! Hey, no problem. First thing is first, let’s remove a factor. Get rid of the excessive heat. That’s right! We have low temperature ink for a reason. Ghosting isn’t the only purpose for low temperature ink but it certainly is near the top of the list. ELT Series, ELT-S Series, and Smart Series are the three low temperature inks we currently offer. ELT and ELT-S will cure as low as 250ºF. Smart Series will cure as low as 280ºF. All three offer a nice cushion below the typical 320ºF to 330ºF cure temperature of most plastisol inks. Choose one of these three inks and you will have the ability to remove excessive heat from the ghosting equation.

If you have been keeping up, we need more than just low heat to prevent ghosting problems. Let’s talk chemistry! OK, we are not going to talk chemistry. Why? Well, lets just say we have our secrets. Do we know what causes ghosting? Sure. Are we going to get into the chemical formulations of our inks? Nope. It’s not really our thing to give away our secrets. However, when it comes to our inks we have the safest possible option which is ELT Series. We are highly confident that you will not ghost any fabric with ELT white and colors when kept at a lower temperature (270ºF and below). ELT-S Series and Smart Series are also ghost-free formulas and only slightly behind the ELT Series in this regard, but they really need to be cured at the lower temperature. At high temperatures (280ºF and higher) we get nervous on some of the most ghost-unfriendly fabrics. Cure this ink properly and we have no worries.

Yes, I did say ghost-unfriendly fabrics. No, I do not have a list of problem brands and style numbers. The reason I cannot provide this is not because there are tens of thousands of styles out there. The problem is that all styles are not created equal.  Consider a typical “moisture management” tee. They wholesale for around $3.50 to $4.00 each. If you order a dozen of these tees today, will they be the same as a dozen from a few months ago? Is the fabric from Honduras? El Salvador? China? Who dyes this fabric certainly matters and it changes not only from style to style, but within the style. There is just no way to know what you are printing before you print a few.

Here is the good news…I know many of the common offenders! I have a nice list of colors and fabrics which may lead to easy ghosting. Of course, if you were listening earlier you are already sold on our low temperature inks and you will not have to worry about much. Regardless, here are many of the “problem children” out there which will require a skeptical eye:

  • Light colors of 100% polyester including: charcoal, light gray, silver, light blue, columbia blue, pink, tan, vegas gold, royal blue, all fluorescent colors, and sometimes black (I know, that one surprised me too).
  • Fluorescent poly/cotton tees. All of them. Keep a close eye on these tricky kids.
  • Pale colors of cotton and poly cotton including: ivory, off-white, tan, khaki, light blue, light pink, you get the idea.
  • Stone-washed tees.
  • Pigment-dyed tees.
  • Any tee which states “vintage” in the description.
  • Tri-blend tees. I would like to state colors here but it is sporadic at best.

This list is specific but don’t think for a second we haven’t seen ghosting on the common fabrics such as a black or navy poly/cotton. I trust zero fabrics unless I am printing with low temperature inks. That’s all there is to it. If you read this and you understand the importance of dryer temperature, give One Stroke Inks a call and ask us about our ELT Series inks. This is a universal ink so it can be printed on virtually any fabric. Make the change and this will be the only ink you need to stock.

 


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How To: Watercolor

Soft hand prints are often demanded by your customers. They saw a tee in the mall and insist a white print on a black poly/cotton should have no feel whatsoever. Perhaps they want a vintage or worn look right out of the box. Regardless, you are a plastisol screen printer and you know they really want that water-based feel. Thanks to some innovation on our part, plastisol can now feel just like water-based ink…and I’m not talking about those high solids water-based inks that feel like a regular plastisol ink. I am talking about a super-soft feel on ring spun, tri-blend, and other premium tees.

Vintage Watercolor

Although Watercolor is much more opaque than standard water-based inks, this is not a high opacity ink you can screen print on top of black fabric and expect vivid results. However, this will provide you with an outstanding vintage or worn look without creating special art work. It is an appearance many of my customers are requesting but they may not be crafty in CorelDraw or Photoshop.

Directions are simple, print through a fine screen mesh and don’t deposit too much ink.  Certainly do not print, flash, and print again. Watercolor is a wet-on-wet ink. There is never a need to flash these inks unless you are printing with them as your general purpose ink on a white base. Watercolor will simply not pick up on the back of the screen and cause a gummy mess. It is designed to “wick” into the fabric, keeping the ink off the next screen and providing that classy soft hand feel.

One important note: When screen printing Watercolor, this ink will only be as soft as the fabric being printed. If you select a cheap poly/cotton tee, expect a cheap feel. This is unavoidable. We push our Watercolor customers into ring spun, tri-blend, burnout, and other soft cotton tees. These premium products will provide a premium look and feel.

Vivid Watercolor

I know, you want that bold scarlet, orange, gold, or white print on a black fabric with virtually no feel. Watercolor can do this…but it comes with a price. Similar to water-based inks, you will need to print a discharge base. This will remove the dye from the fabric leaving a natural color. I really don’t like to recommend the use of a discharge base, or any discharge ink. There are nasty chemicals involved in the process. Unfortunately, this can sometimes be a necessary evil to achieve this look.

The Watercolor inks will easily cover this natural color with a fine screen mesh. Now you have a super-soft feel with a vivid, bold look. Your customers will be thrilled. You didn’t have to deal with the on-press nightmare of water-based inks. Everybody wins!

General Purpose Watercolor

Why wouldn’t you want to print with Watercolor as your general purpose ink? It can do everything Wilflex Genesis and Union Ultrasoft can do. However, Watercolor is softer, easier-to-print, and available in far more colors then either. Watercolor has the opacity and the ability to print wet-on-wet better than any ink I have ever tested. It is an impressive combination.


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ELT-S Series: Let me convince you.

One Stroke Inks is the innovator of true low temperature screen printing inks. First, we pioneered the ELT Series (ELT = extreme low temperature). This ink put an end to so many heat-related screen printing problems. However, this was only the beginning. We needed ELT-S Series.

What does the “S” stand for? The “S” is for stretch and softness. ELT needed an upgrade to handle compression tees, running pants, and singlets. We invented a special S-Additive to allow for these extreme screen printing situations and incorporated it into the already successful ELT Series formula. Obviously, we did not want to compromise bleed resistance or opacity by adding the S-Additive. We had to make some adjustments and improvements as we wanted this new ink to be an amazing improvement. ELT-S Series was born.

With the history out of the way, why should you be screen printing with ELT-S Series inks? The better question is why not? This ink will cure as low as 250ºF. This low cure temperature will prevent so many heat related screen printing problems. These problems include:

  1. Ghosting.
  2. Dye migration.
  3. Fabric discoloration.
  4. Scorching.
  5. Shrinking.
  6. Melting.

How about some other non-traditional benefits? Think about the incredible energy savings you will pocket by turning your conveyor dryers down so dramatically. In my opinion, the energy savings alone makes ELT and ELT-S our most environmentally friendly inks. Your production team won’t mind either. The amount of heat in your shop will be far less abrasive.

ELT-S Series inks don’t just cure at a lower temperature, they flash cure very quickly. Compared to most inks, the flash time will be about half as long. This provides another set of low temperature benefits in which most other plastisol inks cannot compare:

  1. Longer-lasting platen adhesive.
  2. Prevents shrinking which leads to poor color registration.
  3. Prevents dye migration.
  4. Prevents fabric discoloration so common with fluorescent tees.

We also wanted a plastisol ink to replace silicone ink as it is such a hassle to work with. For those not keeping score, here is a list of reasons you don’t want to screen print with silicone inks. Keep in mind all of these statements are found on the silicone ink technical data sheet or sell sheet.

  1. Silicone ink requires a catalyst.
  2. Silicone ink often requires a retardant to improve on-press life.
  3. Silicone ink has on-press life of up to 6 hours.
  4. Silicone ink is only recommended to add enough ink to the screen for 2 to 3 hours.
  5. Silicone ink is not available in a selection of colors, you must custom mix them.
  6. Silicone ink must be cleaned from the screen immediately as it will cure with time.
  7. Silicone ink is not recommended for automated equipment.
  8. Silicone ink is not recommended for “fuzzy” fabric.

As excited as many screen printers were about silicone ink when they first found out about it, these facts inevitably sent them searching for an easier alternative. This is where ELT-S Series comes in. Here is a list of reasons ELT-S Series is a better choice when compared to silicone ink:

  1. Soft/stretchy feel.
  2. Impressive opacity on dark fabric.
  3. Excellent bleed resistance on polyester.
  4. Universal ink. ELT-S will screen print on virtually any fabric.
  5. No catalyst required unless you are screen printing waterproof nylon or waterproof polyester.
  6. It’s plastisol. ELT-S Series can be left in the screen like any other plastisol ink.
  7. Huge color selection with custom color matching available.

Now that I have compared ELT-S to silicone ink, explained the benefits of a quick flash and a low cure temperature, let me tell you why you are really going to make the change. The fact is, you are tired of worrying about expensive fabric. Whether it is a name brand polyester hoodie or an inexpensive neon yellow tee, you don’t want to order one or two more pieces for a screen printing snafu. You don’t want to set that job up again tomorrow for these few replacements. You really don’t want to replace hundreds or even thousands of $65.00 uniforms due to dye migration that did not exist when they left your shop. All of these problems cost you far too much money to keep using high temperature, often ineffective inks. This is a better way. ELT-S gives you the ability to sleep at night. Nobody knows how the next shirt is going to react to your ink or dryer. ELT-S will always give you the best chance at success. I won’t sit here and tell you there will never be a problem with ELT-S in your shop. However, I will tell you there is not an ink on the planet that can do what this ink can do.

Ink Drying in the Screen


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Ink is drying in the screen.

When ink is drying in the screen during a production run, it is most likely caused by the platens heating up excessively. This is a tricky problem as you may be underbasing with white ink or even two screens of white ink. A cool down station may be necessary cool the print and stop the ink from heating up in the screen. If you want to continue with a very fast production, you can try the Production Series inks by One Stroke Inks. These inks will flash and lose their tack in half the time of normal plastisol ink. This keeps the platens cooler and allows production to keep moving. Production Series can help you on cotton, poly/cotton, nylon, and polyester. If you do not want to change inks, test the flash and get it to the quickest possible flash time that you can without the ink remaining wet or tacky. If the ink drying problem is not related to production and you are simply leaving ink in the screen overnight, simply clean the screens at the end of the day. Most inks will clog the mesh when left for this long. Also, you open your screens up to the risk of excessive hazing problems.