Resources What is a Label?

What is a Label?

Labels are die-cut stickers or tags that ID, describe, and track information. They function as simple, ubiquitous tools used to illustrate critical information, provide guidance, and insights into the nature of materials, products, branding, and packaging. Examples we see around us daily of custom labels include food and drug labels, safety labels, branding labels, sterilization labels, etc. While a completed label appears simple in makeup, the construction of the label is far more complex than meets the eye. Consisting of several unique layers, customers must choose carefully as each choice significantly affects how the label will look and ultimately perform. Below, we will cover the basics of labels and how each can impact your product’s configuration and performance. 

CleanMark Labels - Breakdown of a typical label construction


Topcoats are protective layers designed to shield the label from the environment while providing an attractive finish. The most common topcoats come in the form of varnishes and laminates.

  • Varnishes are resin-dissolved liquids that form a shiny transparent film when dry that offers weather and UV protection. 
  • Laminates are transparent films that cover the face stock of the label, offering superior protection against UV, moisture, chemicals, or rough handling.


Ink is a solution containing at least one colorant, such as a dye or pigment, a carrier fluid, and a binder used to color surfaces to produce images, texts, or designs. 
  • Water-based inks are generally the most environmentally friendly and affordable option, with mild to no odor. However, some inks, like dyes, are more prone to UV and water fading. Water-based pigments are more susceptible to rub and scratch failures.
  • Solvent-based inks are often superior for durability or when an aqueous option is impossible for a given application. Solvents do not require topcoats. However, solvent inks can emit significantly more volatile organic compounds (VOCs) than aqueous inks, resulting in solid odors and being less environmentally friendly.
  • Specialty inks are subsets of the ink archetypes used in particular applications, including UV inks, zero scratch resistance, indicators, taggants, etc.


Choosing the right face stock is critical, affecting print and image quality. The face stock is the host surface text, and images are printed onto and are the primary construction component, giving labels their structure, size, and shape. The face stock is primary paper or synthetic.
  • Paper is a classic and inexpensive option for most general applications. Often used on clothing tags and jars, paper is a good choice if a label does not require exceptional durability.
  • Synthetic films are preferable for harsh elements or long-term use. Classic face stock films boast better flexibility and strength, including vinyl, polypropylene, polyethylene, and polyethylene terephthalate. Each type contains numerous subsets with different attributes based on molecular weights, plasticity, price points, durability, and eco-friendliness.


Adhesion is the propensity for two substances to stick to one another. Of all of the layers of labels, the adhesive may have the most significant number of options and conditions to consider when choosing the appropriate adhesive. For example: What are the environmental conditions? What binder type? Is the adhesive compatible with the face stock and liner? What are the VOC and outgassing levels of the adhesive? What surface type is the label applied (high or low surface energy)? Does the application require permanence, clean removability, or repositioning?
  • Permanent typically means the label cannot be removed without damaging the label or surface.
  • Removable adhesives allow labels to be removed intact without leaving residue or a light ring where the label used to be present. This allows for reusing without needing major recleaning.
  • Repositionable is an adhesive that can be removed and reapplied multiple times over its life timeline without fail.

Release Liner

Like face stocks, liners are produced from various papers, plastics, and recyclables. A release liner’s role in the labels includes:
  • Providing a base and protecting the integrity of the adhesive coating.
  • Carrying the label construction throughout the manufacturing process.
  • Carrying a silicone coating that releases the face stock and adhesive together lets the label come off the liner cleanly.
  • Serve as the base for any die-cutting procedure post-construction.

Cores (For Rolls Only)

The core is the ring used in the center of a roll for support to wind up die-cut materials. Core rings are primarily made of rigid cardboard or plastic, each serving different roles.
  • Cardboard cores are the industry standard. Paper-based cores are significantly more cost-effective, practical, and environmentally sustainable. However, cardboard cores can flake and cause tiny dust particles, making them unsuitable for cleanroom applications.
  • Plastic cores are primarily utilized in medical and cleanroom applications. Plastic cores protect against contamination from dust and debris often associated with cardboard cores. Generally, plastic cores are made from either high-impact polystyrene (HIPS), high-density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), and acrylonitrile butadiene styrene (ABS).

Chemical Indicators for Sterilization

Chemical indicators for sterilization labels incorporate chemical indicators to visually confirm the sterilization process completion. These labels go on to sterilization packaging, including pouches, wraps, or containers, to indicate appropriate sterilization processing conditions. Our integrated chemical indicator labels undergo distinct color changes when exposed to specific sterilization parameters, such as temperature, irradiation, gas, etc. The change in color or appearance indicates that the sterilization process has occurred and the contents within the packaging are sterile. CleanMark’s chemical indicators for sterilization labels provide a quick and convenient visual indication of sterilization process completion, allowing you to identify whether the packaged items are sterile easily.

Applications of chemical indicators for sterilization
  • Healthcare Facilities: Extensively used in hospitals, clinics, and healthcare facilities to monitor the sterilization of medical devices, surgical instruments, and equipment. They ensure these items are appropriately sterilized before use, reducing the risk of healthcare-associated infections.
  • Pharmaceutical Industry: Utilized in the pharmaceutical industry to validate the sterilization of drug manufacturing equipment, vials, ampoules, and other packaging materials. They play a crucial role in ensuring the safety and efficacy of pharmaceutical products.
  • Laboratories: Deployed in research laboratories and testing facilities to monitor sterilizing laboratory equipment, glassware, and other materials. They help maintain the integrity of experiments and prevent contamination.
  • Food Industry: Chemical indicators are used in commercial kitchens, food processing plants, and catering facilities to validate sterilizing food preparation equipment, utensils, and food packaging materials. They contribute to food safety and prevent the spread of foodborne illnesses.
Chemical indicators vs. biological indicators

Both biological and chemical indicators are essential in determining successful sterilization. Understanding the differences between the two indicator technologies is vital to understanding the difference between the two indicator technologies. It is important to note that chemical indicators for sterilization labels only supplement more comprehensive sterilization monitoring methods. They serve as an additional layer of assurance in healthcare facilities, laboratories, and other settings where sterilization is crucial to maintain a safe and sterile environment.


Chemical indicator class types

Chemical indicators come in several forms, such as simple test strips, tubes, bowie dick test packs, etc. Despite the multitude of options available, overall, there are six primary classes of chemical indicators per the International Organization for Standardization (ISO):

  • Type 1: Process Indicators

  • Type 2: Specific-Use Indicators

  • Type 3: Single-Variable Indicators

  • Type 4: Multi-Variable indicators

  • Type 5: Integrators

  • Type 6: Cycle Verification 

All chemical indicators must adhere to their guidelines for manufacturing and application standards for each class of chemical indicator. It is essential to know that one class does not outrank another but serves different purposes (see table below).



Type 1: Process



Type 2: Specific-Use

Type 3: Single-Variable



Type 4: Multi-Variable

Type 5: Integrators

Type 6: Cycle Verification

Differentiates processed vs. unprocessed items

Verifies exposure to the sterilization process


Specific test procedure indication

Sensitive only to a single critical variable during sterilization

Exposure to a sterilization process value as a function of time


Responds to two or more critical variables during sterilization

Responds to all critical variables during sterilization

Cycle verification indication

Responds to all critical variables during sterilization


Chemical Indicator Options CleanMark Offers

Design considerations
  1. Compatibility with Sterilization Method: Different sterilization methods, such as steam, ethylene oxide (EO), hydrogen peroxide, or others, have specific requirements and parameters. Ensure that the chemical indicators you choose are designed and validated for compatibility with your sterilization method.

  2. Regulatory Compliance: Verify that the chemical indicators comply with relevant regulatory standards and guidelines, such as those set by the FDA, ISO, or other regulatory bodies. Compliance ensures that the indicators meet specific performance and quality requirements, assuring their reliability.

  3. Indicator Type and Class: Understand the different types and classes of chemical indicators available, such as Class 1, Class 2, and Class 3 indicators. Each class indicates the level of monitoring and verification it provides. Select the appropriate class based on your specific sterilization requirements and risk assessment.

  4. Sensitivity and Response Time: Consider the sensitivity of the chemical indicators to ensure they can detect the sterilization parameters within the specified time frame. The response time should align with the sterilization cycle duration, allowing for accurate and timely results.

  5. Visibility and Interpretation: The color change or visual alteration of the chemical indicators should be easily visible and distinguishable. Ensure that the indicator's response is clear, unambiguous, and easily interpreted by users, reducing the chances of misinterpretation.

  6. Indicator Placement: Proper placement of the chemical indicators is crucial to ensure representative monitoring. Choose indicators that can be strategically positioned within the sterilization load, considering the locations that present the most challenging conditions for sterilization. Proper placement helps ensure that the indicators provide accurate information about the sterilization process throughout the load.

  7. Shelf Life and Storage Conditions: Check the manufacturer's shelf life and storage requirements specified by the manufacturer. Ensure that the chemical indicators have not expired and are stored under the recommended conditions to maintain their performance and effectiveness.
  8. Supplier Expertise and Support: A knowledgeable supplier like CleanMark can provide guidance on indicator selection, usage guidelines, and any troubleshooting or questions that may arise.
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