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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.

 

Ink Cracking


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Why is my ink cracking?

When you are experiencing ink cracking, 99% of the time the ink is under-cured.  This is the time when you need to ask yourself how you are testing the temperature of your dryer.  There are only two acceptable ways to test your conveyor dryer.  First, try using Thermolabels.  These handy stickers will measure the ink at 290F up to 330F with a temperature indicator every 10 degrees.  Once the 320F indicator is completely black, the ink should be cured.  Place the Thermolabel next to the print for best results.  The second test is by using an Atkins heat probe.  This “donut” probe has two cross wires that are designed to be placed in the plastisol ink.  A hand-held device will give you the temperature readings as it goes all the way through the dryer.  Once the ink has reached 320F, it should be fully cured.  Please notice I did not mention a temperature gun.  This will only measure the surface temperature of the ink and this does not ensure the ink has been cured.  Other causes of ink cracking include printing the ink too thin for the fabric, over-curing (not common), and using the wrong ink for the job.  Screen printing stretchy fabrics may require a special stretchable ink.

Plastisol Ink


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What to do with thick plastisol ink?

When a plastisol screen printing ink has been sitting for a long period of time, it often can become very thick.  At this point, many printers will resort to using reducers or additives in the ink to make it more printable.  While this is ok, simply stirring the ink may be all the ink needs to become thinner and more printable again.  Try this before using any sort of additive as anything you add to an ink will have consequences.  If you have tried to stir the ink back to its original consistency and it still is not the viscosity you desire, One Stroke Inks has many options for you.  Curable Reducer is the safest option as you can add as much as you would like without changing the curing properties of the ink.  However, the more you add, the less opacity your ink will have.  Auto Formula Additive is a great option, especially when reducing polyester ink.  This will be less likely to diminish the bleed resistance of the ink.  A new additive is the W.O.W. Additive.  This stands for wet-on-wet additive.  Only used in the 480 Series inks, the W.O.W. Additive is designed to make this ink series better for wet-on-wet printing by preventing the ink from sticking to the back of the next screen.  Visco Minus is a chemical reducer for all inks.  This additive will require very little liquid to reduce a lot of ink.  You benefit by keeping the opacity of the ink higher than what it would be with standard liquid reducers.

Screen Printing Nylon


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Screen printing on waterproof nylon.

When screen printing waterproof or water-resistant nylon jackets, plastisol ink will require a nylon catalyst or nylon adhesive liquid in order to bond fully and create long-term durability. The ratio of ink to catalyst is very important as too little may not adhere to the jacket and too much may cause the print to become brittle. Measure the ingredients by weight. Add 10% nylon catalyst to 90% plastisol ink. It is also important to note the ink may or may not be compatible with the particular nylon catalyst you are using. One Stroke Inks suggests the 222 Series plastisol ink with their nylon catalyst. This combination will give you the durability you are looking for. If the nylon catalyst is added to an ink that is not compatible, you will spot the problem very quickly as the ink will start to thicken up the moment it is mixed up. When you are finished screen printing the nylon jackets, be sure to clean out your screen immediately as the nylon catalyst will cause the ink to harden into the screen mesh after sitting for a few hours. Also, be sure to allow the finished print to sit for 24 to 48 hours before scratching or picking at the print.