Plastic bottle with a waterproof label.

Everything You Need to Know About Waterproof Labels for Your Products

Worried that your labels won’t make it through the lifecycle of your product due to water exposure? Using water resistant labels can alleviate that problem, but with hundreds of inks, coatings and base stock combinations to choose from, it can be hard to find the right solution.

That’s why it’s important to know the limits and requirements for waterproof product labels: that way you can ask the right questions when choosing a label or a labeling machine. Here are some things to consider when incorporating custom waterproof labels.

What’s the Difference Between Weatherproof, Waterproof and Water-Resistant Labels?

Weatherproof labels are designed to withstand outdoor exposure, which can mean different things. UV and temperature resistance is a given, but water resistance can vary widely from product to product. One label may be able to withstand submersion in water, while another label can only handle contact with surface moisture from condensation and precipitation.

When it comes to water-resistant labels and waterproof product labels, the difference comes down to moisture. If a label is water-resistant, it can handle brief contact with moisture, mostly to protect handling of the product until it reaches the consumer. These labels usually have a waterproof coating, but the label stock isn’t waterproof. If water reaches the inside of the label, it will disintegrate. 

Water-resistant labels are mostly used on jars and frozen food products because moisture exposure is minimal. Condensation isn’t often an issue in a refrigerator, because, at most, frozen foods need to survive layers of frost, and temporary exposure to water when this ice melts. 

Waterproof labels, by comparison, can withstand prolonged contact with moisture, and these labels are mostly used on beverages, personal hygiene products (like shampoos, lotions and soaps) and cleaning substances. Oil-resistance and waterproof stickers are imperative for these items because the branding and safety/ingredient information needs to remain intact throughout the life of the product. 

What Makes a Product Label Waterproof?

Water resistance depends mostly on three parts of the label: label stock, adhesive and coatings.

With label stock, the choice seems obvious: paper fails when it comes in contact with water, while most plastics are at least water-resistant. (However, you can get good water resistance from paper with the right coating.) Paper stock is usually the cheapest option, while bi-oriented polypropylene (BOPP) is the most popular choice for water-resistant labeling. Vinyl and polyester are waterproof, but these high-quality durable label materials are more expensive than paper. 

There are a wide range of adhesives available for pressure sensitive labels, so there’s no one-size-fits-all choice for waterproof product labels. However, it’s important to keep in mind that removable adhesives usually have poor moisture performance.

Waterproof coatings protect the label stock and ink. On labels that use paper stock, the laminate will stop water from reaching the face of the paper, but some water can reach the edges, and possibly blur your label design. These coatings may interfere with direct thermal and thermal transfer printing, because they fully encapsulate the print and any open pores on the surface of the label stock. This can keep the heat from a thermal printer from accurately altering the color of the paper, while the ink from thermal transfer printing has trouble bonding to the coating’s slick surface.

Is Thermal Transfer or Direct Thermal Printing Waterproof?

Direct thermal printing uses heat to darken the surface of the label. This process isn’t affected by moisture. However, direct thermal paper performs poorly when exposed to environmental stresses, particularly light. Over time, the entire surface of the label will darken. In most cases, this alone makes direct thermal labels a poor choice for products that also require moisture protection.

That said, there are weatherproof thermal labels that can withstand short-term use for shipping. These labels will fade after a few months, but they’re fine for the days or weeks it takes to go from your factory to the end user.

Industrial thermal transfer printing should be waterproof. Instead of spraying or dabbing ink onto the label, thermal transfer printers melt the ink onto the surface, creating a permanent bond. However, some coatings can interfere with this process.

Is There a Standard for Testing the Water Resistance of a Label?

Answer: not really. Regulations around water resistance are vague. For example, the FDA’s Quality System Regulation Labeling Requirements, which applies to medical devices, only requires labels to be intact with clear print during distribution, storage and use. There is no set standard that these labels have to pass to meet these conditions.

There also aren’t label testing standards from any of the major regulatory bodies, including ASTM, ISO, DIN and JIS, which makes it hard to compare the performance of labels from different manufacturers. In response, some companies have adopted ISO 6425 for testing their labels. (This is a standard developed for certifying dive watches.) 

Obviously, most of this standard doesn’t apply to this testing – your labels don’t need to be tested for magnetic resistance, or have a unidirectional bezel that lets your customers monitor their oxygen consumption. What label makers use from this standard for, though, is the submersion test. The label is submerged under a 30 centimeter (12 inch) column of water for 50 hours to test its water resistance. Since ISO 6425 has been in use for 25 years, equipment and information on testing methodology is readily available.

What Else Should I Consider When Choosing a Water-Resistant Label?

  1. If you want to use thermal transfer printing, you need ribbons that are compatible with your roll labels, and BOPP, paper, vinyl and polyester need different ink formulas to get even adhesion.
  2. Be sure your labels can handle all the environmental factors at play, not just water resistance. Outdoor labels see repeated cycles of heat and cold, both from day to night and through the seasons. Consider if your label needs to be uv-resistant. Remember, even labels with UV resistance will not retain full color forever. 
  3. Frozen foods are exposed to extreme cold that can make adhesives and plastics of any size label brittle. Cryogenic labels, used mostly on laboratory sample test tubes, must also survive extreme temperatures and be moisture-resistant to prevent damage from frost and condensation.
  4. While an adhesive may be waterproof, that doesn’t necessarily mean it will cure on a wet container. If your products (like beer bottles with rounded corners) are covered in condensation when they reach the labeling machine, you either need a compatible adhesive or you need to install an air knife to wipe off the surface before application.

What Labeling Machines Can Accommodate Waterproof Product Labels?

The great thing about pressure sensitive labeling is that you can easily switch between standard and custom size labels without needing to change equipment. For example, at CTM Labeling Systems, our wine bottle labeling machine is extremely dynamic. 

This machine supports single labels, front and back labeling with two label applicators, and front and back labeling with a single applicator that alternates labels. It also supports cover labeling, so you can add or cover information as needed for different markets or regulatory changes. Add water-resistant labels, and you’ll never need to worry about labels falling off when customers place the bottle in a wine chiller. As long as these labels are within the machine’s size ranges, it can apply your waterproof labels quickly, accurately and efficiently. 

Of course, not all containers have a shape as simple as a bottle. Our 360a Series Form, Fill and Seal (FFS) labeler has an extendable snorkel that can get into hard-to-reach areas, like raised lip lids.This makes it ideal for a wide range of food containers, as accessibility is key to affixing labels to odd shaped product packaging

A Labeling System that Works with Your Production Needs

If you’re looking to improve your labeling system, contact CTM Labeling Systems. We’re ready to work with you to get your labeling application processes at optimal production levels (whether you use regular or waterproof product labels): shipping boxes, bottles, food containers or pharmaceuticals – you name it, we can do it.