Custom Printing: Direct Digital Printing on Bottles

I was reading the trade journals online this week, keeping abreast of trends in commercial printing, and I came upon an article written by Pat Reynolds in Packaging World (www.packworld.com) entitled “Direct Digital Printing on Rigid Containers.” It was published on 4/3/18.

I know this sounds somewhat dry as a subject, but as I read the article, I saw the implications for packaging, marketing, and digital commercial printing in general. Plus, it was interesting to see just how printing can be done on a bottle without using a label. So I did further research.

The Background

First of all, I think you will appreciate the concept more if I first give you some background on how this would have been done before digital custom printing. The options would have been as follows:

Label printing. This would have worked fine, printing on matte crack ‘n peel label stock and then affixing the labels on the bottles. However, there would have been a number of steps involved. It would not have been a direct process, and presumably all of the labels would have been identical. Granted, in more recent times, a printer could have produced digital labels, which could easily have included variable data. But the labels still would have had a border. That is, the packaging art would have been limited to the dimensions of the label.

Screen printing. A printer could have used screen printing technology to image the packaging information right on the bottle without needing a label. This would have been less confined in its design than a rectangular label. Printed imagery could have extended onto any portion of the bottle accessible to the custom screen printing equipment. More than likely, the screen and the squeegie used to force ink through the screen printing mesh would have been stationary, and the bottles would have been spun around on their vertical axes to bring each bottle’s surface into contact with the printing screen.

Presumably, since custom screen printing ink is very thick and tacky, there would have been limited resolution in any photographic images (which probably would have been too challenging to attempt anyway), and since a new screen would have been needed for each color, the majority of screen printed imagery would have been limited to a few colors.

But more than anything, this process would have required extensive make-ready. Therefore, for the job to be competitive in price, a long press run would have been necessary. Also, variable data printing would have been out of the question. All art would have been static. All images would have been identical. Moreover, since screen printing make-ready is so labor intensive, the process would have taken a long time.

Pad Printing. Another option would have been pad printing. This is great for printing on golf balls and computer keys. Even if a surface is rounded, like a bottle, successful screen printing requires the screen to come into direct contact with the printing substrate. This alone would make screen printing on many shapes of bottles impossible. That said, a gravure printing process called pad printing, or tampography, would be an option. In this process, a gravure plate is covered with ink that quickly becomes tacky as it dries. Then a silicone pad is brought down onto the inked plate, where it picks up the tacky ink image as the pad compresses briefly. Then the pad can be positioned over the substrate (which can be concave, convex, or any other shape that would otherwise be difficult to print). Finally (due to the nature of the silicone pad and the ink) the silicone pad releases the tacky ink image onto the substrate.

However, like screen printing, pad printing artwork cannot be changed for every image, and, given the make-ready involved, pad printing also lends itself to longer press runs.

Enter Direct Digital Printing

Reynolds’ article describes the new process of direct digital printing on PET plastic and glass bottles used for the food and beverage industry. Within the context noted above, being able to print on irregularly shaped surfaces (as you might do with pad printing) while constantly varying the imagery is rather exciting.

Moreover, you could conceivably create only one printed bottle if you needed a prototype. Then, you could make any design changes required and print the entire run with the new design. And you could do this with FDA compliant, low-migration, food-safe inks.

To give you an idea of the technology involved, a system of feedscrews and a starwheels brings each cylindrical bottle in front of the digital inkjet printheads, using a carousel system to move the bottles through the system and out again. Reynolds’ article, “Direct Digital Printing on Rigid Containers,” describes transport systems that can be built to accommodate more bottles at a time (increasing the speed and efficiency of production depending on the run length).

The article also describes two printing processes, one that involves inkjetting the cyan, magenta, yellow, and black ink colors sequentially, and another that deposits the inks all at once. To make all of this work, certain bottle shapes will be more successful and certain shapes will not work.

Addressing the needs of both PET plastic bottles and glass bottles can be tricky, due to the different heat requirements for the two substrates, but Reynolds’ article explains how each can be accommodated.

The process uses UV-cured inks, which will set instantly upon exposure to ultraviolet light (provided by LED bulbs). This allows for printing on non-porous substrates (such as PET plastic and glass) and makes the bottles immediately usable without any drying time. In addition to the usual process colors (cyan, magenta, yellow, and black), the technology uses white inkjet ink and also a clear primer to make the ink adhere better to the substrate.

Why This Is Special

Direct printing on PET and glass bottles provides several benefits for the food and beverage packaging industry.

1. 1. You can produce an edition of one. This is useful if you’re making a prototype for a bottle. The mock-up will look exactly like the finished product.

1. 1. When you have confirmed your initial design, you can still make each bottle different, so each customer who buys the product can have unique personalization (such as their name).

1. 1. Although there are some limitations in the substrates (the bottles have to be a certain shape that will allow access to the inkjet heads: cylindrical but not oval, for instance), I’m sure the ability to print digitally on uneven or irregular surfaces will improve in the near future. (For example, I have read about inkjet equipment that can already print directly on a football.)

1. 1. The UV inks are “low-migration” inks that won’t contaminate the food products in the bottles.

1. 1. On a design level, you have a larger area for the custom printing. You are not limited to the rectangular dimensions of a label. The imagery and text can be positioned on any part of the bottle’s surface accessible to the print heads.

1. Unlike screen printing and pad printing, digital inkjet custom printing allows for high resolution photographic imagery. This could make the look of a direct digital printed bottle far more dramatic than that of a screen-printed or pad-printed bottle.

More than anything, this is a good, solid step in the direction of printing almost anything on almost any substrate.

This entry was posted on Sunday, November 4th, 2018 at 8:39 pm and is filed under Digital Printing. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.