Challenges in Glass Bottle Coding

As stated above, date coding on glass bottles is essential for industries that produce and package perishable goods, as it conveys important information about the product. This information is useful to both the manufacturer, who uses batch numbers for quality control and logistics purposes, and to consumers, as it clearly states the product’s expiration date.

However, as in any mass production, glass bottle coding, or coding on any type of glass container, is all about the volume and the ability to print on as much glass in as little time as possible. It may sound unreal, but it’s not uncommon for bottling companies to date code print on 100,000 bottles every hour. This means that the coding process has to be reliable and fast on top of being legible.

Glass bottle coding isn’t as easy as it sounds due to inherent challenges associated with printing on glass.

Printing on glass has its own set of challenges due to the material properties of glass. Many consider glass to be fragile, implying a lack of strength, but that’s far from true. Glass isn’t fragile; it’s brittle and often used for its strength and recyclability.

What makes glass bottle coding so challenging is the fact that glass is a non-absorbent material with a relatively smooth surface and a frequently curved form. This makes the material very hard to print on, as the non-absorbance means that the ink takes longer to dry and cure, the smooth surface might promote smears, and the curved surface area might affect the consistency of the print.

This issue of non-absorbency is mostly solved by using fast-drying inks, while modern printers have their way of dealing with glass bottle curvature, such as using specialized print heads. However, ink selection is also an issue, especially when printing on returnable bottles, which rely on a special, washable ink. The ink has to be durable enough to withstand the rigors of bottling, storage, distribution, transport, and use by the end consumer without being erased in the process.

However, once the bottles are collected and returned to the bottling company for reuse, replacing the glass bottle coding with a new expiration date and lot number is necessary.

Learning how to print on glass bottles involves overcoming the aforementioned challenges associated with glass bottle coding by using specialized equipment application-specific ink and considering environmental factors.

Acquiring a good-quality printer is paramount to producing legible glass bottle coding, and most industries typically rely on several different printer types, including continuous inkjet printers, laser printers, and UV inkjet printers.

Naturally, this affects ink selection. Continuous inkjet printers are the most versatile type, as they print using a wide variety of inks and on several different substrates. Laser printers provide precise and high-quality glass bottle codes and are suitable for environments where ink-based systems aren’t ideal for use. The last is the UV inkjet printers, which rely on inks that cure under UV light—and require specialized ink.

Overall, ink selection is important since it needs to stand out against the background, which is usually the bottle's content, implying the use of pigmented ink, which settles after a period of inactivity within the printer. The ink has to overcome condensation by penetrating and adhering to the bottle surface despite condensation. This also applies to specific inks resistant to condensation that form after printing.

Glass bottle coding is typically done at the bottling company at volumes and high production speeds, making continuous inkjet printers one of the most viable options for glass bottle coding due to their versatility and the ability to print at high speeds.

As their name implies, continuous ink printers rely on the continuous flow of ink mixed with a solvent from a reservoir. The ink is pumped from an ink reservoir through a nozzle and is broken up into a large number of ink droplets through high-frequency vibration.

Once the droplets are formed, select droplets are charged by electrodes. The stream of droplets then passes through deflector plates which create an electrostatic field. The charged drops are deflected as they move through the deflector plates, to be ejected from the print head and placed on the product to form the required message.

Droplets that haven’t been electrically charged are recirculated back into the system to be reused. ink travels from a reservoir, passing through a nozzle, and then fragments into numerous tiny droplets by vibration at a high frequency.
There are several benefits provided by CIJ printers for glass bottle coding, including accurate and high-quality print that adheres to the surface and dries fast. Furthermore, the continuous flow of ink prevents the ink from clogging the print head, leading to maintenance reduction costs.

If you’re interested in glass bottle coding and are in the market for glass bottle coding printer equipment, don’t hesitate to contact KEYENCE and inquire about our line of continuous inkjet printers.