Cold Foil Best Practice Series 3:
Cold Foil Troubleshooting for Flexo Printers

In our cold foil best practice blog series, we’ve discussed best practice for successful wet lamination cold foil printing.  Previously, we’ve shared information on proper press set up to ensure successful cold foil printing in our part 1 blog: Proper Press Set Up for Successful Cold Foil Printing and choosing the right print variables and job set up best practice in blog #2 on Cold Foil Job Prep & Production Best Practices.

Now that we have prepared the press, and run the cold foil job, you may have encountered some obstacles along the way. As a leading provider of metallic and holographic cold foil substrates, the specialty print specialists at K Laser Technology have the knowledge and experience to help you troubleshoot common cold foil defects to achieve successful cold foil printing in flexo. In this final blog for our cold foil best practice series, we’ll highlight the problems you may encounter, what may be the cause and how you can fix it to get production up to speed in no time!

Common Cold Foil Print Defects

Here are some of the common foil print defects you may encounter in your print applications:

There are 3 main reasons your foil doesn’t transfer at all. (1) You may have the wrong web path set up, (2) the adhesive may be uncured, or (3) you may be using the incorrect foil or adhesive. If you have the wrong web path set up, it’s important to locate a nip station (entry nip) immediately after the print station that will be printing the adhesive. You must ensure you re-web the press so that the substrate enters the nip station immediately after the impression cylinder. Please review the first blog in our series for more information on proper web path set up. If your adhesive is uncured, your substrate may be passing through the dryer too quickly or the dryer is not at the right setting for the press speed. Move the dryer to a higher setting, decrease the speed of the press or both. If neither of these solves the issue, you may be using the wrong cold foil or adhesive. Consult with your cold foil supplier on the proper foil for your print application.

If you find that your foil is adhering in the beginning and then begins failing in production, the culprit may be your anilox rolls. More than likely, your anilox cells are plugged with adhesive and no longer transfer to the substrate for foil adhesion. Wash down the print station with Xylene, acetone and vinegar and let dry. The adhesive left in the ink pan will still be viable and within no time you should be able to run the job again with no issue.

We understand speed is vital for a profitable operation. If your foil will only adhere at speeds less than 50 fpm, there may be one of three components causing this issue. (1) The anilox cells are plugged, (2) the dryer capacity is too low and not able to penetrate through the foil, or (3) the foil is not formulated for the wet-lamination cold foil process. If the problem is the anilox, clean the roll as stated above. If the problem is the drying capacity, check UV dryers for contaminated lamps or reflectors or install a second dryer to assist. Check with your cold foil supplier that you are using the right cold foil for your application.

When the foil is not transferring evenly across the web, this is usually an issue at the nip point. Either your nip pressure is uneven, your nip roll is worn or grooved or there is poor alignment with the nip roll. To resolve this issue, you should adjust the nip pressure until you see the foil transferring evenly, try replacing the roll if it is damaged or reinstall the roll being mindful of alignment.

If there are lines showing across the web, check that the stripping angle is correct and change as needed. If that is not the source, then your web may be touching the dryer frame. Check the web path and make sure it remains clear of the dryer frame or any other components in that area.

If the foil is not being transferred with enough pressure, this again is an issue with the nip roll. You should try to increase the nip pressure to begin. It may be that your nip roll is too soft. Replace the nip roll with a higher durometer nip to resolve.  If all else fails, your nip roll may be out of alignment – reinstall the nip roll being mindful of proper alignment.

Are you seeing large holes in your image? The culprit is most likely contamination: contamination in the plate, the substrate or the anvil or nip roll. To resolve this, clean the plate, anvil and nip roll and consider investing in a web cleaner, a tacky roller, or a tacky cloth to keep the web clean.

If your final cold foil image appears smudged, you may be using too much adhesive or the nip roll is too soft. Readjust the plate cylinder settings to a kiss pressure to pick up adhesive uniformly or replace the nip roll with a higher durometer roller.

This is usually caused by the foil tension being too high or the foil sticking to the nip roll. Focus on decreasing the tension in the laminating arm and waste windup section and give your nip roll a good cleaning to ensure it is free of foil or adhesive waste.

If you’re seeing foil in areas where it should not be, it is likely caused by dirt on the idler roller or on the nip roll. Clean the rollers and you should be free of this issue.

If your image is smeared, this is an issue with the web path. Check you have the proper web path set up and make sure the printed image isn’t touching an idler roller. Review proper web path set up in our first blog in this series.

If you see these defects in your cold foil, you may have the incorrect plate cylinder setting or low nip pressure. Adjust the plate cylinder and increase the nip pressure to achieve more crisp, sharp foil edges.

Are you seeing wrinkles across your foil ruining the shine and sheen of your foil printing. There are a couple reasons this may be happening: (1) you have incorrect foil tension, (2) you have an incorrect foil path, (3) the UV dryer is too hot or lastly (4) the idler roller is not properly aligned. If the issue is with your foil tension, adjust the tension in the laminating arm and waste windup until the wrinkles are no longer visible. You also should evaluate the web path and re-web the foil if necessary. If your dryers are too hot and cracking the foil, check or change your UV lamps, lower the dryer settings, or increase your run speed.

If you’re seeing a faded foil image or a fisheye skewing effect, your foil and substrate may not be perfectly laminated at the point of cure. Install an idler roller under the UV lamp and adjust the foil tension to ensure the image does not skew or become faded.

Experiencing pinholing in your images? The nip pressure may be too low or there is not enough adhesive resulting in the foil not transferring thoroughly. Increase the nip pressure to resolve the low nip pressure or replace the anilox roller with a lower lpi to transfer more adhesive to the substrate.

If your foil is prone to scratching or rubbing off, your adhesive may not be fully cured, the UV lamp may be too low, the foil is of poor quality or you have the wrong adhesive. Any of the following may resolve the issue: decrease your running speed to cure the adhesive, increase the lamp power, or reach out to K Laser Technology and consider switching your cold foil provider for a better foil product. Speak with a K Laser Cold Foil Specialist to check you’re using the proper adhesive too.

From proper press set up to choosing the right job components to troubleshooting for foil defects, you now have all the tools you need to print brilliant cold foil applications with confidence. We hope this blog series has helped you take full advantage of the wonders of cold foil printing. At K Laser Technology, we take great pride in providing the industry’s most extensive range of cold foil colors and holographic patterns, enabling you to achieve the pinnacle of foil printing excellence. To further support your creative packaging journey, we invite you to visit our state-of-the-art Cold Foil Design Lab. Located in Sarasota, FL and staffed with our creative team, K Laser Technology can assist you with print designs & inspiration, print & digital mockups, and foil printing best practice. We have over 30 years’ experience working with flexo printers and designers on special effects packaging design. In your pursuit to become a master of cold foil printing, we are here to support you every step of the way. Feel free to reach out to our team to discuss your cold foil substrate needs and specialty packaging designs. We eagerly await the opportunity to assist you!