How to avoid bubbles during laminating?
Bubbles are caused by a lot of problems: insufficient tension on the supply roll; feeding the leading edge of the print too quickly into the laminator; too much heat on a wet print, causing “outgassing” of the ink; the adhesive not bonding properly to the media, and others.
Insufficient tension causes bubbles when air gets trapped between the film and image because the film wasn’t taut as it entered the nib (caused by lack of supply roll tension). Insufficient tension is obviously fixed by adjusting the tension of the feed spool to the proper specifications for the type of film you’re using. Thinner film needs less tension, for instance. Too little supply roll tension will cause bubbles before it will cause wrinkles in the film.
Feeding too quickly causes bubbles if the item is pushed into the rollers faster than the speed of the laminator. The solution to this problem is too obvious to mention.
The heat issue like “hot spots” is a key problem when laminating inkjet prints. Inkjet printers dump a lot of ink onto the print, and a rushed operator may try to laminate the image before the ink is completely dry. The problem can be exacerbated by the fact that if a laminator is allowed to sit for extended periods of time without the rolls turning, there can be varying degrees of temperature on different parts of the rolls. This creates areas called “hot spots.” If you’re running a laminator at 85°C, the point where the rolls sit together can easily become a hot spot of ±95°C. When a moist inkjet print encounters one of this hot spot, the ink can easily boil, creating bubbles. Among the solutions to heat-related bubbling is not to let your rolls sit idle for extended periods of time, to speed up your laminator so less heat gets into the print or to work with at about around 40°C during your cold laminating and 90°C during your hot laminating and always use the appropriate pressure.
The silvering is caused by the capture of tiny bubbles of air. It looks like a hazy or reflective area in the lamination. It may go unseen over light areas of an image, but will be more obvious over dark or black areas. Silvering is usually caused by too low an operating temperature.
Silvering is most often seen when a machine is not given time to warm up or if the film temperature drops too low. When a large machine is warmed up without the motor on, one side of each laminating roll remains relatively cool. When lamination is begun, a pattern of repeated silvering can be seen each time the cool side of a roller is applied to the lamination.” cool spots”–areas that aren’t hot enough to melt the adhesive. If you see bands of silvering alternating with bands of properly adhered areas, it means one part of your roller was too cool.
Pay attention to watch for any defect which repeats. This is typical of debris, damage, or low temperature on a section of the roller. On the other end, bubbles can also be caused if the adhesive doesn’t bond properly to the image. It can look like sheen on your image. Bonding problems can also be caused by inadequate heat, inadequate or uneven pressure, or too much speed. Inadequate pressure can cause silvering because the film wasn’t pressed onto the image hard enough, preventing the adhesive from properly bonding.