It’s how grocery stores manage the freshness of their inventories, and it’s how customers know they’re getting a safe product. If the expiration date is smudged during printing, packaging, or transportation, store policy may not allow the product to reach the shelf. Even if that smudged product does reach the shelf, customers may avoid it altogether. Poorly printed expiration dates can lead to wasted product and materials.
Choosing the best expiration date stamp for plastic bottles helps prevent this waste. It also helps to simplify the lives of retail stock and auditing staff—leading to better relations with your retail partners and a better grip on the bottom line.
Food and Drug Administration Product Dating Requirements
The expiration stamps for plastic bottles are a type of food product dating that is governed by the Food and Drug Administration (FDA). The only food product for which an expiration date is required by federal law is infant formula. In all other cases, it’s voluntarily provided by the manufacturer.
There are two types of dates that might be found on a plastic bottle. On the one hand, you have the date of bottling for a product: what FDA terms a “closed” date. On the other hand, expiration dates fall under a different category termed “open” dating.
The only requirements the FDA sets for open dating is that it not be misleading to the customer. In other words, it should be prefaced by terminology like “best by,” that makes it clear that the date is a suggestion and not a hard and fast rule for disposal by that date. In the case of long-lasting, shelf-stable, or frozen products, open dating must include the year as well as the month and day. Whether a manufacturer is using an open date expiration stamp for plastic bottles or a closed date that shows when the product was bottled, the printing challenges are going to be largely the same—related to plastic type, shape, and volume.
Printing on Different Types of Plastics
The plastics that are typically used for bottles and other containers are thermoplastics: a range of different plastics that can be heated up, molded into the desired shape, and then heated up again and molded into a new form. It’s this resiliency that allows most plastic bottles to be recycled. Within this category, there are several different types of plastics that are commonly used to make plastic bottles for consumer products.
Some of the particular plastic surfaces you might be dealing with include:
- Polyethylene terephthalate (PET): PET has a very smooth, non-absorbent surface, similar to glass.
- Polycarbonate (PC): Polycarbonate plastic is strong and translucent with a higher gloss finish that imitates glass.
- Low-Density Polyethylene (LDPE): LDPE is lightweight, robust, and squeezable for contents like condiments—and it’s a more expensive material.
- High-Density Polyethylene (HDPE): HDPE is a denser and less-expensive version of LDPE. It has a high resistance to stronger solvents and creates a stronger scent barrier, but it’s not as smooth as many other plastic types.
- Polypropylene (PP): Polypropylene is highly resistant to heat and is commonly used to make bottle caps.
- Polyvinyl Chloride (PVC): PVC provides a particularly strong barrier—against oils, odors, and gases—making it ideal for cleaners and other household products. Well known for the inclusion of plasticizers, PVC may not be approved for use alongside products for human consumption.
The challenges of printing on different types of plastics are only party due to the differences of the plastic surface. Specifically, PET, PP, and PC plastics all present a notably smoother surface than that of plastics like HDPE. But the curves of a bottle present a whole new challenge. And the properties of the materials that go inside of these bottles can present just as much of a problem for printing and stamping.
A soy sauce bottle with a glossy coating of polycarbonate will provide a challenge not only because of the smooth surface, but also because an expiration date for plastic bottles containing soy sauce must be printed in an ink that contrasts with the dark liquid. Milk bottles will be labeled while cold, and moisture condensing on their surface may present additional problems for printing that must be solved up front. You need to understand the particular conditions you’re printing under as you approach a solution. These challenges—and many others—can be addressed through the choice of a quality ink and printer.
Printing an Expiration Date Stamp for Plastic Bottles
Issues like smooth surfaces and condensation are best addressed with a quick-drying ink that hardens as it dries. These are inks that can also be used to print dates on glass surfaces. It may surprise you to learn that a carefully designed inkjet printer can easily manage bottle curvatures and concavity and print quick-drying inks on a variety of different plastic surfaces. These printers can manage this critical job for product volumes much greater than other types of expiration date stamps can manage for plastic bottles—providing a more consistent, reliable solution overall.