HOW TO EVALUATE THE WATER RESISTANCE OF SELF-ADHESIVE LABELS?

  

I. Basic Judgment: Initial Screening Based on Material Combinations

The water resistance of self-adhesive labels is determined by the combination of "facestock + adhesive". A preliminary judgment can be made based on material types to quickly eliminate obviously non-water-resistant options.

  

Water Resistance of Facestock

Non-water-resistant / Weakly water-resistant: Ordinary paper materials (such as offset paper, kraft paper), which absorb water easily and deform or cause ink to smear when exposed to water, are directly excluded from water-resistant application scenarios.

Water-resistant: Film materials (such as PET, PE, PVC, OPP), which are high-molecular polymers and do not absorb water, are the basic facestock for water-resistant labels; some specially treated paper materials (such as coated copperplate paper), with a waterproof coating on the surface, also have certain water resistance, but are not as durable as films.

Water Resistance of Adhesive

Non-water-resistant: Ordinary water-based adhesives, whose adhesion rapidly decreases when exposed to water and may even fall off, are only suitable for dry environments.

Water-resistant: Solvent-based adhesives, hot-melt adhesives, or special waterproof adhesives, which maintain stable adhesion when exposed to water and are less likely to fall off, should be used in combination with waterproof facestock (if waterproof facestock is paired with ordinary adhesive, the label may still fall off due to adhesive failure).

  

II. Practical Testing: Three Simple Methods to Simulate Real Scenarios

After the basic judgment, practical tests are needed to verify the water resistance. The following three methods can be quickly implemented at home or in the workshop and cover most daily water-resistant scenarios.

1. Immersion Test: Simulating Long-Term Water Contact Scenarios

Suitable for labels that need to be immersed or remain in a humid environment for a long time (such as beverage bottle labels, bathroom product labels).

Test Steps:

Completely immerse the product with the label attached (or attach the label sample to the same carrier) in room-temperature clear water for 24-48 hours.

After removal, observe if the label has fallen off, wrinkled, or delaminated (separation of the facestock from the substrate).

Dry the surface with a dry cloth and check if the printed patterns/texts have smudged or become blurred. Gently rub the print layer with your fingers to see if there is any color loss.

Passing Criteria: The label does not fall off, wrinkle, or delaminate, and the printed content remains clear without color loss.

2. Spray Test: Simulating Short-Term Water Splash Scenarios

Suitable for labels that may come into contact with splashing water (such as kitchen cleaner bottle labels, outdoor product labels).

Test Steps:

Use a spray bottle (or adjust a faucet to a fine mist mode), and spray water continuously onto the label surface from a distance of 30 cm for 10-15 minutes (simulating daily splashing water).

After stopping the spray, observe if the label has curled edges or partially fallen off. Gently push the edge of the label to see if it is loose.

After natural drying, check if the print layer is intact and if there is any blurring of the text due to water penetration.

Passing Criteria: The label has no curled edges or loose/peeling parts, and the printed content remains intact.

3. Friction Test: Simulating Wear Scenarios in a Humid Environment

Suitable for labels that may be touched or rubbed in a humid state (such as hand sanitizer bottle labels, skin care product bottle labels).

Test Steps:

Use a damp cloth (with moderate moisture content, not dripping) to repeatedly rub the label surface with moderate force (simulating daily touch), about 50 times.

Observe if there are any scratches or damage to the facestock, and if the print layer has been rubbed off or exposed.

Check if the bond between the label and the carrier has curled edges or fallen off due to friction and moisture.

Passing Criteria: The facestock is undamaged, the print layer shows no significant color loss, and the label has no curled edges or fallen off.

  

III. Professional Testing: Scenarios Requiring Third-Party Laboratories

If the label is used in special industries (such as food contact, medical, long-term outdoor use), more precise professional testing is required, mainly focusing on two indicators: Water Resistance Grade Test

According to national standards (such as GB/T 1733-1993 "Test Method for Water Resistance of Paint Films", which can be referred to for labels), within a specified temperature (e.g., 40°C) and a specified time (e.g., 96 hours), the weight change and appearance change of the label in distilled water are tested to evaluate the water resistance stability.

  

Adhesive Holding Power Test

According to GB/T 4851-2014 "Test Method for Holding Power of Pressure Sensitive Adhesive Tapes", a certain weight (e.g., 1kg) is applied to the label surface and placed in a humid environment. The time the label remains attached without falling off is tested to determine the adhesive's durability in a humid environment.

  

Key Points to Note: Avoid Misjudgment

Distinguish between "surface water resistance" and "overall water resistance": Some labels are only water-resistant on the surface material, but the adhesive is not. Short-term splashing may be fine, but long-term immersion will cause the label to fall off. Special attention should be paid to the water resistance of the adhesive.

Consider the influence of temperature: Labels that are water-resistant at room temperature may have reduced water resistance in low-temperature (e.g., refrigerator) or high-temperature (e.g., near a kitchen stove) environments. Targeted tests should be conducted based on the actual usage temperature.

Waterproof treatment of the printing layer: Even if the surface material and adhesive are water-resistant, if no waterproof treatment is applied during printing (e.g., no waterproof film is applied or no waterproof ink is used), the printed content may still bleed when exposed to water. It is necessary to confirm whether the printing process is waterproof.

If you need to assess the water resistance for a specific scenario (such as "food labels in a refrigerator" or "shampoo labels in a bathroom"), I can help you compile a targeted water resistance test procedure list. Do you need it?