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Screen Printing: Process + Techniques
How to Prevent Ghost Images
October is here and there is nothing like a good ghost story to make your hair stand on end. The ghosts in our story aren’t souls of the dearly departed, but they will haunt you nonetheless.
Say you printed an order of shirts, boxed them and sent them on their way. Nothing was out of the ordinary during your print job, so you go on the rest of your week as usual. Then your customer calls about their shirts and complains that you did something wrong and their shirts are ruined. When you get the shirts back, you notice a silhouette of the image printed on the backs and bottoms of each shirt.
The images are the result of a ghosting problem. Not real ghosts though. The Ghost Busters aren’t going to be able to help you out with this one, but luckily you aren’t the only one plagued by this epidemic. Ghosting is a problem that every screen printer will probably run into at least once in his or her career.
What is Ghosting?
Ghosting is the disappearing, or fading of the garment’s color, directly under the printed area of stacked garments. This typically happens when printing low-bleed white ink on a colored shirt. There always is the possibility that the colored dye of the garment will come through the white ink printed on it. It is tempting to use a low-bleed ink to prevent any dye migration from occurring, but in fact low-bleed ink rarely stops the “bleeding” that occurs during dye migration.
Ghosting can occur for a multitude of reasons, which makes it all the more maddening. Here are a few reasons you might experience ghosts haunting your garments:
- Excessive PH left in the garment from the manufacturer
- High humidity in the shop
- Moisture in the garments
- Certain garment colors
As mentioned, certain colored garments can trigger ghosting. Colors like light blue, yellow, green and violet are all offenders. Your dryer also can be a part of the problem. If it has a short heat chamber, there is less time for moisture to evaporate to allow the ink to cure. If you try to run the belt at a slower speed and crank up the heat, then the shirts come out at a really high temperature. Stacking hot shirts can contribute to ghost images.
How to Prevent Ghosting
As with any of the issues that may arise in your shop, they typically are solved by going back to the basics of screen printing. Having the right mesh, good squeegees, proper off-contact and good screen tension are best practices when printing. Make sure that you use the appropriate ink for the job. Garments made of 100% cotton call for cotton ink, and 50/50 blends call for low-bleed ink. Keep moisture and humidity low in your shop.
Consider pulling the shirts out of the box and running fans or the air conditioning to allow any moisture to evaporate. If you have any concern that your garments may be susceptible to ghosting, avoid over flashing or over heating the shirts in the dryer. You want to cure the ink properly, but stacking hot shirts will cause the colors to distort due to the dyes in the garment.
Just like on any of the ghost hunter TV shows out there, there are tests that you can use to determine if your garments are haunted — no Ouija board needed.
- Print your ink onto a piece of the same fabric that will be used for the order.
- Take your test piece and place it in a heat press. Spray with a light mist of water for moisture.
- Cover the printed area with a blank piece of the same suspect fabric (sandwiching the print). Set the heat press to 250°
- Close the heat press and let it sit for a half hour before visual evaluation.
- After a half hour, check for ghosting on the unprinted piece of material.
If the material is prone to discoloration, you will see a ghost image of your printed image on the material that was covering the printed area. Spooky!
Mary Yaeger is a webmaster for Texsource Screen Printing Supply, managing their online presence including social media. She can be reached at firstname.lastname@example.org. For more information on Texsource, visit screenprintingsupply.com
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