Whether you’re running water-based or UV/LED inks, heat and humidity have a direct effect on performance, from ink adhesion to substrate handling. Below, we dive into three key challenges that surface in the summer months—and our expert’s recommendations to help you beat the heat.

Humidity Hazards in Ink Transfer and Adhesion

There are two ways that humidity can disrupt your print performance. The obvious one is muggy conditions in shops with no climate control. But even if you’re beating the heat inside with air conditioning and de-humidifiers, as you bring in your rolls of material from delivery trucks outside and place them on your shop floor, you may be facing some condensation issues—especially if those materials are placed directly on press without having time to adjust to the new ambient temperature.

No matter how humidity is being introduced to your print process, it can lead to a decrease in the surface energy of your substrate leading to poor ink adhesion, mottling, or other ink laydown issues. Avoid quality inconsistencies and material waste due to humidity by taking some precautionary steps in your operations. 

What to do

If possible, aim to keep your pressroom conditions at 45–55% relative humidity and under 75°F.

Don’t leave rolls on trucks or in loading bays during peak heat.

Allow substrates time to cool after being delivered.

Test your substrate with dyne pens before press runs and utilize a corona treater when needed.

Summer-Proof Your Storage

The pressroom isn’t the only area that suffers in the summer. Substrates stored in hot, unventilated warehouses can degrade quickly. Pressure-sensitive label rolls exposed to excessive heat may experience adhesive bleed, edge ooze, or even roll telescoping. Shrink films stored above 90°F can warp and distort from the heat, affecting registration and print quality.

What to do

Store sensitive substrates below 80°F in low-humidity rooms.

Rotate inventory using FIFO—older stock will degrade faster in hot conditions.

Store label stock vertically when possible to reduce adhesive pressure on roll edges.

Consider investing in insulated storage or HVAC upgrades for warehouse spaces.

Beat the Heat with UV/LED Curing

Traditional mercury vapor curing lamps emit a lot of infrared heat, raising web temperatures significantly. This only exacerbates heat-related issues during the summer months, which is especially problematic for label stocks, where heat can soften pressure-sensitive adhesives, or prematurely distort shrink films.

By contrast, UV and LED technologies cure at much lower web temperatures, helping printers maintain substrate integrity even on the hottest days. Beyond just label compatibility, UV/LED systems also reduce the need for heavy ventilation and climate control, lowering air conditioning costs and reducing pressroom energy consumption.

What to do

If you’re already considering making the switch to UV/LED curing technology, this could be an added benefit. Ask your press manufacturer or lamp supplier for more detailed cost savings projections to understand your potential ROI.

Summer Success with Smart Printing Practices

While you can’t change the weather, you can adapt your processes to maintain quality and performance all summer long. By understanding how heat and humidity affect your substrates, inks, and equipment—and by investing in temperature-friendly technology like UV/LED curing systems—you’ll be better equipped to handle seasonal variability without sacrificing consistency.

Zeller+Gmelin has decades of experience formulating high-performance UV and LED ink systems specifically designed for label and packaging printers who demand stability, efficiency, and brilliant results—even in the toughest pressroom conditions. Whether you’re facing ink transfer challenges or planning a shift to low-temperature curing, our team is here to help.

Contact your local Zeller+Gmelin representative to learn how our UV/LED ink solutions can support your operation this summer—and beyond.

The post Surviving Summer in the Pressroom: How to Protect Ink Adhesion and Label Quality first appeared on Zeller + Gmelin.

As experts in formulating compliant UV/LED inks, coatings and adhesives, we’ve put together this FAQ to break down the essentials of Prop 65—so you can focus on your business, not the fine print.

1. What Is Prop 65?

Proposition 65, formally known as the Safe Drinking Water and Toxic Enforcement Act of 1986, is a California law designed to safeguard residents from exposure to chemicals linked to cancer, birth defects, or reproductive harm. It mandates that businesses provide warnings if their products contain significant levels of these substances, such as lead, phthalates, or formaldehyde.

2. Who Must Comply with Prop 65?

Compliance is required for any business selling or distributing products in California, or manufacturing items that may reach California residents—including those based outside the state. This applies to business owners, printers, and compliance managers in the print and packaging sector. Exemptions exist for companies with fewer than 10 employees or products with chemical levels below designated “safe harbor” thresholds.

3. Which Chemicals Are Covered?

The Prop 65 list started with 30 chemicals in 1986 and now tops 1,000, all identified as potential carcinogens or reproductive toxins, with new chemicals added to the list every year. It includes substances that affect print and packaging manufacturers such as heavy metals, phthalates, bisphenol A (BPA), styrene, and certain solvents used in inks, coatings, and adhesives. View the full chemical list on the OEHHA website: https://oehha.ca.gov/proposition-65/proposition-65-list

4. When Is a Warning Required?

A warning is necessary when a product exposes users to a listed chemical above its “safe harbor” level. These thresholds—NSRL (No Significant Risk Level) for carcinogens and MADL (Maximum Allowable Dose Level) for reproductive toxins—determine compliance. If no safe harbor level exists for a chemical, businesses must evaluate exposure risks to decide if a warning is needed.

5. What Does a Prop 65 Warning Entail?

A Prop 65 warning must contain the word “WARNING” in bold and must be clear and reasonable, typically featuring language like:

WARNING: This product can expose you to [chemical name], which is known to the State of California to cause cancer and/or birth defects or other reproductive harm. For more information, visit www.P65Warnings.ca.gov.

These notices may appear on product labels, websites, or in-store signage to inform consumers effectively.

6. How Can I Ensure My Products Meet Prop 65 Standards?

For printers, your choice of substrate, inks, coatings and adhesives will affect your Prop 65 compliance. Speak to your suppliers about testing inks, coatings, and packaging materials for Prop 65-listed chemicals. Compare results to safe harbor limits (where applicable) and maintain thorough documentation. Partnering with a forward-thinking ink supplier like Zeller+Gmelin, who prioritizes formulation compliance, can streamline this process.

7. What Are the Consequences of Non-Compliance?

Failing to comply can lead to steep penalties—up to $2,500 per day, per violation. Costs can escalate quickly with multiple products or prolonged exposure. Enforcement comes from the California Attorney General, district attorneys, or private citizens acting in the public interest, making adherence critical.

8. How Does Zeller+Gmelin Support Compliance?

We understand the complexities of Prop 65 packaging requirements. Zeller+Gmelin is dedicated to developing inks, adhesives and coatings that meet regulatory standards without compromising performance. Whether you’re producing labels or packaging, our expertise ensures your materials align with Prop 65 requirements for printers. Have questions or need tailored solutions? We’re here to assist.

Your Partner in Prop 65 Compliance

Mastering Prop 65—from its chemical list to its warning protocols—doesn’t have to be daunting. Zeller+Gmelin is your trusted partner in navigating these regulations with confidence. Contact us today to learn how our compliant inks and coatings can support your business.

The post Prop 65 Frequently Asked Questions: Essential Insights for Print and Packaging Professionals first appeared on Zeller + Gmelin.

At Zeller+Gmelin, we manufacture high quality dual-cure UV/LED inks that print on shrink seamlessly. In this blog, we’ll review some essential quality control properties and testing methods that can elevate your shrink sleeve printing game.

Quality Control Properties

Ensuring quality involves testing several critical properties:

• COF (Coefficient of Friction) – Kinetic and static
• Adhesion
• Shrinkability
• Blocking
• Flex

Each property contributes to the overall performance and durability of the shrink sleeve. Here’s how to test and manage them effectively.

Testing Procedures and Best Practices

1. COF (Kinetic and Static)

The coefficient of friction (COF) plays a crucial role in the application of shrink sleeves. Customers may require either slippery or controlled COF depending on their equipment.

Kinetic COF: This measures friction in motion, such as sleeves sliding over bottles. Too low, and the sleeves may bunch up; too high, and they may not slide properly. Typical ranges are 0.2–0.3.

Static COF: This measures the force needed to overcome static friction, crucial for preventing blocking when sleeves are stacked. Typical ranges are 0.2–0.6.

Testing Tip: Use a slip/peel tester under ASTM D-1894 standards for accurate COF measurements. Note that slide angle testers only measure static COF.

2. Adhesion

Adhesion ensures the ink bonds securely to the substrate. For UV shrink inks like NUVAFLEX which achieve shrink percentages similar to solvent gravure inks, adhesion testing goes beyond basic tape tests.

• Use crosshatch testing with standard 3M 600 or 810 tape.
• Activate adhesion with in-line corona treatment rather than focusing solely on dyne levels.

3. Shrinkability

Shrinkability is critical to ensure that the ink film adheres smoothly and resists defects like microcracks or flake-off.

Testing Methods:

• Boiling water soak (30 seconds): The most aggressive and revealing test.
• Industrial hot air dryer: A more practical, everyday option.
• Steam kettles or blowers: Also effective for shrink testing.

Check for smooth shrinking with no durability issues, opacity loss, or matting.

4. Blocking

Blocking can occur if sleeves cling or stick together, impacting application performance and final product quality.

• Simple Test: Fold a printed article ink-to-ink, press it with your thumb and forefinger, and check if the layers slide cleanly.
• Advanced Testing: Use slip/peel equipment for a more detailed analysis.

Proper curing tests confirm that the ink doesn’t stick to itself or the container in high-humidity environments.

5. Flex

Flex testing evaluates how well the printed ink withstands crumpling and twisting.

• Bicycle Crumple Test: Hold a sample in both hands, twist it in opposite directions, and inspect for flaking or cracking.

Flexibility testing ensures the ink can endure the rigors of shrink application and handling without compromising quality.

Final Thoughts

UV shrink sleeve printing is an art and science, and quality control is the glue that holds it all together. From COF to flex testing, each procedure offers insights that help you refine your process and deliver exceptional results to your clients.

By mastering these testing techniques, you can avoid costly reprints, reduce waste, and build trust in your printing expertise.

Need advice on inks or testing procedures? Contact the Ink Experts at Zeller+Gmelin—we’re here to help you achieve shrink sleeve perfection!

The post Key Testing Procedures for UV Shrink Sleeve Printing first appeared on Zeller + Gmelin.

As a leader in UV ink solutions, Zeller+Gmelin has provided this guide to help you avoid common mistakes and adopt best practices for managing your printing ink inventory.

The Importance of Ink Inventory Management

Raw material mismanagement causes a host of pain points for industrial printing operations. As one of the highest cost consumables and a driving factor for print quality, ink management is especially important to maintain profitability and customer satisfaction.

Effective inventory management ensures high quality inks are available when needed, helping you avoid downtime and expedited shipping costs and improve material utilization. Plus, a reliable ink supply supports on-time order delivery and consistent print quality.

Common Pitfalls in Ink Management

Knowing the risks of inventory mismanagement is the first step, avoiding these common mistakes is the next. Zeller+Gmelin is a leading provider of printing inks for flexo, offset and commercial applications. With over 150 years in the business, here’s some of the common inventory mishaps we’ve seen that affect printers’ bottom lines.

Overstocking or Understocking: Excess inventory ties up capital and risks obsolescence, especially with UV/LED inks which have a shorter shelf life than others. While understocking can lead to production delays and expedited shipping costs, reducing your profit margins and productivity.

Inadequate Rotation: Failure to rotate your inventory and follow the FIFO (First In, First Out) method is a leading cause of ink expiration. Using expired ink may result in improper curing or adhesion and color inconsistency.

Improper Labeling: Mislabeling or lack of tracking, leads to confusion about ink age, type, or intended use. Poor label practices could increase the likelihood of accidental use of expired or incorrect inks as well as cause delays in production to find the right inks or resolve labeling issues.

Lack of Usage Monitoring: Not keeping accurate usage data can result in inaccurate forecasting and missed opportunities to optimize ink ordering. Profit margins dip when expedited shipping is needed to produce an order on time.

Poor Container Sealing or Storage: Open or improperly sealed containers can lead to contamination, drying, or curing of inks. Be aware of incorrect temperature, humidity, or exposure to light. These factors can degrade the ink over time or cause premature curing resulting in more ink waste.

Without a proper ink management system in place, these inventory mistakes can negatively impact your daily operations  and may be the culprit of low profit margins affecting your bottom line.

Z+G Inventory Tips for Success

Avoiding common inventory issues doesn’t require complex methods, you can start with simple improvements that make a big impact. These tips from our team of experts are actionable steps that you can take in your ink room.

Use an Inventory Management System: Implement software to track ink inventory levels, expiration dates, and usage trends. This can be as easy as a spreadsheet or software on a dispenser. More advanced tracking software can integrate with your production schedule and equipment, such as automated dispensers with built-in tracking sensors for ink usage monitoring in real time.

Adopt FIFO Practices: Standardize your ink receiving process to always rotate the oldest inventory to the front and place newer products behind, following the FIFO method to reduce waste. Confirm expiration dates when rotating to ensure the inks expiring first are easily accessible.

Standardize and Label Clearly: Label all containers with batch numbers, production dates, and expiration dates. Use color-coded systems for quick identification between ink types or applications. Using QR codes, barcodes or RFID tagging can make stock tracking more efficient and reduce manual errors. Periodically, inspect labels to make sure important information is not worn or torn off – relabel as needed.

Set Minimum and Maximum Thresholds: To maintain balance, define reorder points and maximum stock levels for each ink type. Use consumption data from your tracking system, set up automated alerts in your software, and take note of supplier lead times to optimize this component of ink management.

Dispose of Expired Inks Safely: Create standard operating procedures related to the disposal of each ink type used in your pressroom, to ensure environmental and employee safety. Incorrect disposal of expired inks can harm the environment and increase disposal costs, not to mention that failure to correctly manage hazardous materials can result in fines or legal issues.

Conduct Regular Training: Train staff on proper handling, storage, and inventory practices for UV/LED inks to minimize human error. Establish clear protocols for leaks, contamination and light exposure to effectively address potential storage issues and/or safety concerns. Standardize these ink management processes in written format and incorporate them into your onboarding programs for all applicable employees.

The Importance of Regular Audits

Conducting ink inventory audits at regular intervals is another way to prevent issues like overstocking, misidentified, and expired inks. We recommend creating a schedule or checklist to standardize the process.

 For larger operations with significant ink usage (over 20,000lbs/month), monthly audits ensure that your inventory remains manageable and optimized. Smaller printers with stable usage patterns can typically operate on a quarterly audit schedule to maintain order.

Spot audits are good practice when discrepancies are expected or after significant events like an ink room move or a new press install. Operations of all sizes should consider annual comprehensive reviews to reconcile inventory data with physical stock and to review supplier performance.

Ink Storage Best Practices

Protect your ink quality with this checklist for storage best practices.

Control the Environment: Maintain appropriate temperature and humidity based on ink type. UV inks require cool, dark storage, ideally between 60°F–77°F (15°C–25°C) to prevent premature curing.  Whereas, water-based inks need protection from freezing, which can break down their formulation and render the ink unusable. Humidity can cause some inks to thicken or separate, as well as increase the risk of microbial contamination in water-based inks.

Maintain Proper Seals: Use airtight lids and reseal containers completely and immediately after use to prevent contamination or curing. Inspect seals for wear and tear during your audits and replace any damaged lids or gaskets promptly.

Store Away from Direct Light and Heat: UV-sensitive inks and coatings can cure or degrade with exposure. Make sure UV/LED inks are stored in opaque containers and stored away from direct sunlight or artificial light.

Check Condition Regularly: Inspect containers for leaks, rust, or swelling, and take immediate action if found. Swelling of containers can indicate contamination or chemical reactions within the ink and should be addressed immediately. Log your inspections and analyze the data for recurring issues or trends in deterioration.

Segregate Storage: Store inks by type (UV, solvent-based, water-based) and label the areas clearly to avoid cross-contamination. Store inks used for specific applications, such as specialty or food-safe inks separate from your general use inks. Also be sure to create a clearly marked “waste inks” area for any products that need to be disposed of according to regulatory guidelines.

Proactive ink management will lead to smoother operations and ultimate cost savings for you, and better quality for your customers. Get started today with Zeller+Gmelin to avoid production delays, improve production efficiency, and maintain regulatory compliance.

Ready to optimize your ink room setup? Our team can help with auditing your current inventory and providing recommendations for improvement. Contact the Zeller+Gmelin team for ink and coating solutions, expertly done.

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Zeller+Gmelin is a proud manufacturer of a variety of lightfast inks for sheetfed offset, web offset, dry offset and flexo printing applications. To achieve acceptable lightfastness, Zeller+Gmelin uses high-quality pigments, dyes, and formulations resistant to UV radiation and other light sources. Verified through extensive testing, Z+G lightfast inks are proven to withstand the degrading effects of light exposure and retain their original colors and appearance over an extended period.

Advantages of Lightfastness

In printing, lightfastness is a key consideration for ensuring that the printed graphics maintain their vibrancy and clarity over time. Products and posters exposed to sunlight or artificial light sources for prolonged periods can experience color fading or changes, leading to a loss of visual appeal and potential damage to a brand’s image. There are many advantages to using lightfast inks:

Print Protection. Lightfast inks resist discoloration and fading due to exposure to prolonged periods of light. This ink characteristic is an important factor in maintaining the brand image through various environments and uses. Lightfast inks maintain print permanency and brilliance throughout the product lifecycle. Products exposed to constant sunlight such as horticulture tags, garden and pool supplies, utility buckets, and outdoor signage can remain vibrant and accurate to the original print, when using lightfast inks. 

Chemical Resistance. Lightfast pigments are known for their resistance to various forms of light, but they can also be formulated to withstand exposure to various chemicals during the filling process or throughout product use. For example, lightfast horticulture tags may come into contact with fertilizer, sprays or water, which require special ink formulation to avoid damage from chemicals or moisture.

Compliance & Permanency. Some areas of packaging are extremely important to maintain throughout product use in order to protect the safety of consumers. Product descriptions, instructions, warning labels and compliance information are crucial to proper product use and consumer safety. These print sections musts be maintained throughout the entire product life cycle. Lightfast inks can be used to ensure the permanency of these important safety features of your packaging.

Recyclable Packaging. If your containers and packaging are designed to be recycled, lightfast inks are a good option due to their ability to adhere effectively to the print material and not bleed into the wash cycle during recycling. If the pigments were to degrade in the wash, it could detrimentally color the plastics to be recycled and reduce the material’s recyclability.

By using inks with excellent lightfast properties and selecting appropriate materials, printers and manufacturers can ensure that their products maintain their visual appeal, brand integrity, and product quality throughout their intended lifespan, along with the consumer safety and environmentally friendly benefits.

Measuring Lightfastness

When developing fade-resistant inks, our pigments are chosen to meet minimum Blue Wool Scale standards (ISO 105 B02) of 5 through 8 when lightfastness is required in the final product application.  To determine lightfastness of printed products, Zeller+Gmelin conducts various tests under controlled conditions, simulating real-world exposure to natural outdoor light and weathering conditions using a Xenon Arc fadeometer.  By conducting controlled exposure tests and using color measurement techniques, the lightfastness of printing inks can be accurately evaluated and chosen to ensure the longevity and visual quality of your final printed product.

It’s important to consider that the measure of light degradation depends on several variables. For example, print exposed during July may last 20 – 25 days, while the same print exposed in November could theoretically last up to 140 days.

Additionally, you may want to subtract additional days for differences in latitude, altitude, location, exposure to air pollution and other chemicals, humidity, and weathering effects. The bottom line is that, while the Blue Wool Scale is useful in choosing the correct pigmentation for your product, the customer must ultimately monitor and test their own results under their unique application and field conditions.

Important Considerations for Lightfast Printing Inks

There are several important factors to consider when deciding on lightfast inks and which Blue Wool Scale rating is needed for your application. Here are some print best practices and “need-to-know” information from the ink specialists at Zeller+Gmelin:

Lightfast inks are available in a limited number of pigments and are not available for bright fluorescent or pastel colors. These inks tend to use darker and “dirtier” pigments to withstand the elements and light exposure for long periods of time so it is important to ensure the print design can be achieved with these specialized pigments.

Not all coatings are compatible with lightfast inks and can reduce the effectiveness of their fade resistance properties. Check with Zeller+Gmelin to ensure your coating effectively maintains lightfastness in the various field environments required.

If your product is intended to be used for an extended period, it is best to use lightfast inks to maintain the packaging print throughout its full product use – or at least in the instruction and compliance sections. This can ensure your brand colors stay true and important information does not fade over time.

Lightfast and “weatherable” are two different characteristics of inks. If your product is used and stored outdoors, the ink must be both lightfast and weatherable. Whereas, if your product is solely used indoors, then lightfast ink will suffice. Weatherable inks are always lightfast, though lightfast inks are not always weatherable.

Remember that the lightfastness of the pigments will vary relative to your final product application and exposure. Be sure to test the print under your unique conditions to ensure it will withstand the degrading elements found in your desired environment.

Zeller+Gmelin Ink Specialists are knowledgeable in lightfast and weatherable inks and can assist you in choosing the best color solution for your print application. Contact our team to learn more about this important ink characteristic and discover the best rating recommended to achieve your print and brand goals.

Advantages of Lightfast Inks

Lightfastness is the ability of printing inks to resist fading or discoloration when exposed to artificial or natural light. It is a critical characteristic, particularly in applications where the final product will likely be displayed, stored or used in well-lit environments, such as retail shelves or outdoor settings. READ MORE

Download Lightfast Infographic

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Understanding Lightfast Inks

Lightfastness is the ability of printing inks to resist fading or discoloration when exposed to artificial or natural light. It is a critical characteristic, particularly in applications where the final product will likely be displayed, stored, or used in well-lit environments, such as retail shelves or outdoor settings. READ MORE

Read Lightfastness Blog

The post Advantages of Lightfast Inks (INFOGRAPHIC) first appeared on Zeller + Gmelin.

De-Ink Rigid Plastics with EarthPrint Eco-Friendly Inks

Years ago, ink manufacturers were tasked with the challenge of formulating robust inks for rigid plastics that adhere incredibly and never wash off. Now, ink producers are being challenged with the exact opposite… READ MORE

Read EarthPrint Blog

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From your morning cup of coffee to the millions of packages delivered daily, flexographic printing has found its place all around us. Flexographic printing is a versatile and widely used production process that caters to many industries. Also known as “flexo printing,” this technique combines letterpress and rotogravure elements to create high-quality prints on a wide variety of substrates.

Zeller+Gmelin has been a leading producer of UV and LED flexographic printing inks for decades. This blog will discuss how flexographic printing works, its typical applications, and its advantages and disadvantages. For any questions or to discuss your unique flexo operations, please get in touch with Zeller+Gmelin. We’re here to serve you!

Understanding Flexographic Printing

“Flexo printing” refers to a relief printing process that uses flexible plates made from rubber or polymer materials. These plates are wrapped around rotating cylinders on the printing press. The image areas on the plate are raised, while the non-image areas are recessed. The ink is transferred to the printing plates via an anilox roll or sleeve and transfers the image onto the substrate as it passes through the rolls, creating a printed impression. Flexographic printing presses are manufactured in 4 main formats, according to the size of the printing web: narrow-web, mid-web, wide-web, and corrugated. All in all, flexographic printing is a prevalent print method used for various applications and produced worldwide.

Equipment Involved in Flexographic Printing

Printing Plate

Printing plates serve as the image carrier in the flexo printing process. They are typically made of rubber or polymer material and engraved with the raised image areas used to transfer the ink to the substrate. Printing plates are wrapped around a printing cylinder to create a continuous surface. Each color or element of the design usually requires a separate printing plate.

Anilox Roll

The anilox roll is a crucial part of the flexo printing process. Its primary function is to uniformly distribute solvent-based, water-based, or UV/LED inks onto the printing plate in a consistent even layer. Anilox rolls are engraved with thousands of microscopic cells, and as they rotate in the ink reservoir or ink chamber, the engraved cells become filled with ink while a doctor blade removes the excess ink. The anilox then comes in contact with the raised image on the printing plate and transfers a uniform layer of ink to be printed on the substrate.

Anilox cells can be laser, mechanically, or electromechanically engraved and come in various geometries. The most popular cell geometry is the 60˚ Hexagonal, but anilox engravings also come in 45˚ Quad, Longcell, Channel, Trihelical, Positive, and many more!

Substrates

Flexography can print on various substrates, making it a suitable printing method for multiple products. The choice of substrate depends on the specific requirements of the product being printed. Common substrates include:

Paper: This common substrate comes in various forms, from coated papers for labels to packaging.

Paperboard: A thicker, sturdy material, paperboard is used for food and consumer packaging, such as cereal boxes, cosmetic cartons, and beverage packaging.

Plastic Films: Flexo printing is well suited for printing on flexible packaging materials such as plastic bags, shrink sleeves, and pouches.

Foils: To add an embellished finish or a decorative shine, flexo printing can utilize metallic substrates.

Corrugated board: From simple brown boxes with black text to eye-catching point-of-purchase, corrugated board is a typical substrate in flexo printing.

Printing Cylinder

Printing Cylinders carry the printing plates and transfer the inked image onto the substrate using precise pressure. Multiple cylinders can be used for multi-color printing processes.

Dryer

After printing, the substrate passes through a dryer section that evaporates the solvents from the ink, leaving a dry and finished print. If you’re using UV or LED inks, this section will consist of high-powered UV/LED lamps that quickly convert the ink into a solid before the next print station.

Common Applications of Flexographic Printing

Packaging

With the capability to inside print and produce packaging at a high volume, flexo printing is extensively used for packaging such as food packaging, cosmetics, pharmaceuticals, protective folding cartons, product labels, flexible packaging, and much more!

Corrugated Packaging

In the production of corrugated boxes, flexographic printing is used to add block letter print and icons or more detailed branded designs to the corrugated board’s outside and/or inside surface. Examples of corrugated flexo print are packaging for electronics, furniture, shoes, eCommerce, logistics, and other consumer goods.

Labels

Flexo printing is preferred for producing labels for food and beverage, wines & spirits, cosmetics, pharmaceuticals, and logistics. The ability to print vibrant, high-quality labels efficiently and achieve specialty print effects in narrow web flexo makes this printing method a popular option for label applications.

Flexible Packaging

The flexibility of flexographic printing makes it a go-to choice for producing flexible packaging materials like stand-up pouches, bags, sachets, shrink sleeves, and more. It can handle the unique requirements of these materials, such as heat resistance, full branding wraps, tamper resistance, and product security.

Advantages & Disadvantages of Flexographic Printing

Flexographic printing offers several advantages:

Quality: When all processes and print components are controlled, flexo can achieve an impressive level of print quality for its customers. With optional units for cold foil, specialty coatings, and varnishes, flexo printing can achieve an incredibly stunning print at a more cost-effective price.

Versatility: Flexography can print on a wide range of substrates, making it a flexible printing option suitable for various industries and applications. Many flexo presses are modular, capable of adding specialty units for full, one pass, in-line production.

High Speed: Flexo presses can achieve high production speeds, over 500m/min, making it an efficient option for medium to large print runs.

Cost-effective: Flexo printing is more cost-effective than offset printing and can achieve quality for medium to large print jobs more economically. Cleaning and maintenance costs are also more economical than other printing methods.

Alternatively, flexo printing also has some disadvantages:

Image Resolution: Compared to offset printing, flexo has some limitations in achieving high-resolution images though, this difference is becoming smaller daily.

Setup Time: The job changeover and setup process for flexo printing can be time-consuming. However, many OEMs have created quick changeover systems, improving set-up times tremendously.

Not ideal for Short Runs: While it is efficient for medium to large print runs, flexo printing is less cost-effective for short runs due to the investment in plates, ink, and anilox rolls, along with the setup times involved.

Here for the Long Run

Flexographic printing has carved its niche in printing technologies for decades. Its wide range of applications, efficient production capabilities, high-quality end products, and cost-effectiveness make it a popular printer choice. However, its limitations in image resolution and suitability for short runs should be considered when selecting the printing method for the job. As technology evolves, Zeller+Gmelin will continue to be at the cutting edge of flexographic printing, offering high-performance UV and LED printing inks for your most challenging applications. As you begin or continue your journey into flexographic printing, consider the ink specialists at Zeller+Gmelin for any questions or opportunities. To learn more about Z+G flexographic inks, click here or contact our team to discuss your unique print goals.

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What is Shrink Sleeve Printing?

To begin, let’s first clarify what shrink sleeve printing is. Shrink sleeve printing is a unique and effective print process where the ink is printed on the inside of a special shrink material utilizing either the flexo or digital print process. The printed material is then seamed and subjected to heat through a heating tunnel, heat gun, or other heating method to shrink the material seamlessly to the distinct shape of the final product.

There are multiple advantages to shrink sleeve printing.

• Full Wrap Packaging. Shrink sleeves provide a full wrap application allowing a much larger print area for high quality graphics, promotional messages and product information. This makes shrink sleeves a popular choice to improve marketing and branding, differentiating the product on the shelf.
• Tamper Evident. The tight fit of a shrink sleeve can cover the entire product, including the cap or seal, providing a tamper-evident enclosure to ensure product integrity and consumer safety.
• Durability. Considering the print is on the inside and protected by the shrink film, this print application is known for its incredible durability against moisture, fading, abrasion and heavy product use, keeping your packaging attractive throughout its product lifecycle.
• Versatility. Shrink sleeves can be applied to various container shapes and sizes making it a versatile option for a wide range of products.
• Recyclability. As more eco-conscious consumers demand sustainable packaging, shrink sleeves are a way to easily remove the printed non-recyclable material without impacting the recyclability of the product container. PSLs and direct print can leave behind residue that impacts the recycling process.

Key Components to Shrink Sleeve Printing

Shrink sleeve printing differs greatly from traditional pressure sensitive label (PSL) printing. With different materials, a different application, and a finishing process, you must control three key areas for successful shrink applications.

#1. Shrink Materials

Shrink substrates are traditionally made of a single layer plastic or polyester material that is stretched and “frozen” in place. These materials are much thinner than the dual-layer paper and plastic substrates found in traditional label printing. As a result, shrink materials are more prone to web breaks and must be handled with precise tension control utilizing web tension technologies. The material must also be compatible with the inks and the press configuration. Because shrink materials are known to have low surface energy, a corona treater is often recommended to increase ink adhesion, though it is important to test the settings to ensure optimum performance.

Shrink substrates are also assigned a percentage of shrinkage and durability. Take the time to speak with your supplier and understand the shrink percentage needed for your application and apply accordingly. As the material runs through the press, keep in mind the substrate is sensitive to heat. The press may heat up, as industrial machinery often does when run at high speeds. Therefore, chill drums are an important part of the process to prevent pre-shrinking the material on press. Shrink materials require much more care and attention than traditional label stock, so careful control and maintenance of these materials are crucial to successful shrink printing.

#2. Press Configuration

For printers running shrink sleeves, you should maintain a few features on your press to precisely print and control the shrink film material. Before running the press, printers should run the material through a corona treater. The corona treater increases the surface energy of the shrink film using a high frequency electrical discharge. This improves the ink adhesion, printability, durability, and the overall quality of the print. This will also reduce ink smudging or flaking during sleeve application and product use.

Web tension and cooling are also critical components of successful printing on shrink films.  As stated above, shrink films are much thinner than other print materials and are sensitive to heat within production. To prevent web breaks and control the temperature, web tension technologies and chill drums must be used to maintain the integrity of the material. Web tension control systems ensure the film maintains a constant and controlled speed at the desired tension throughout the entire print process and during the pre-print process of corona treatment. The tension control system will prevent the material from stretching/breaking and prevent wrinkles and print defects while maintaining accurate print registration and alignment. This will enhance the overall productivity of the press and the quality of the final printed product.

Chill drums, also known as chill rollers or cooling drums, play a crucial role in rapidly cooling down the printed shrink film after ink adhesion or the curing stage. This cooling is necessary to maintain the material temperature, set the ink, and stabilize the printed film for final sleeve production. It’s important to note that the design and temperature of the chill drum must be carefully controlled for optimum results. Chill drums that are too cold or inadequate will lead to print and performance defects in the shrink material. It is a common myth that MORE chill is best, but in our experience, the web temperature will depend on your curing system, press speed and other processes unique to your print environment. Don’t just put your chill rollers to maximum. Find your chill drum “sweet spot” for the best results.

Your curing system is another press component that will greatly impact the quality of your printed shrink sleeves. Considering the material’s sensitivity to heat, it is crucial to clean and maintain your UV or LED bulbs, reflectors, and press speeds to effectively cure your inks and control the shrink of the film.  As your curing system ages, it will generate more heat and fewer UV rays resulting in warped materials and less reactivity from the ink. Failing to maintain or replace your UV systems or bulbs will throw money down the drain with more material waste due to shrinkage and poor product quality from poor ink adhesion. Another common myth is that LED curing systems don’t give off heat and therefore will not require a chill drum – WRONG. LED systems may not put out heat itself, however the ink will react to the LED curing process and give off heat during the chemical reaction. Whether you use LED or UV curing systems, it is still important to use web temperature controls.

Although all press components are important for proper print, finding the optimal settings for your corona treater, web tension control system, chill drums and curing system will be the key to successful shrink sleeve printing.

#3. Inks & Coatings

Inks and specific pigments have a special relationship with the curing process that can affect your shrink sleeve printing quality. Considering the effect of heat on the shrink film material, ink colors are known to absorb or reflect different levels of the UV spectrum resulting in some interesting outcomes in shrink. It’s important to note that dark colors such as blacks, blues and purples will absorb a large part of the UV spectrum, resulting in more heat input on those areas of the print, making it more prone to shrink. At the same time, light colors will reflect a large area of the UV spectrum, energizing the print around it and moving the heat to other areas of the film. Shrinkage is inevitable, but preparing your systems for the level of pre-shrink dependent on the print colors and areas will be the best way to remain proactive against material warping.

Additionally, the temperature of the web can impact the ability of the ink to cure or adhere to the film material properly. Though it’s important to keep the web cold, if the web is too cold the ink will not have the proper chemical reaction needed to adhere to the substrate. This can result in improper slip out of whites or tacky, smudgy print. An optimal press configuration is required for proper ink performance.

Before moving any further, speak with the ink specialists at Zeller+Gmelin. It is vital that we understand the final print product and application to recommend the proper ink and cure settings for print excellence. For example, if your shrink labels are put on the container prior to the filling process, they could be exposed to abrasive chemicals that impact the ink if they come between the container and shrink sleeve. Or let’s say the finishing process uses a water-based seaming solvent that separates the pigment from the ink and bleeds throughout the substrate. Opting for a chemical-resistant ink or a slip layer coating in these situations is necessary to ensure product integrity – but of course you must ask those questions to the customer to understand the entire production process and identify where and when these ink properties are needed.

Shrink Sleeve Best Practice

At Zeller+Gmelin, we always recommend a shrink performance test be conducted prior to full production. A proper test will ensure the artwork is correctly designed and distorted to shrink and seam properly, the material is at the correct shrink percentage and the ink used can withstand the chemicals exposed during production. Do not print within the folds or at the seam to avoid cracking in your final product. Alternatively, you can design the artwork where the cracking looks intentional in the design. To increase the eco-friendliness of your shrink sleeve packaging, utilize a PVC-free film made from bio-based materials along with low migration inks, compliant with all regulatory applications, from Zeller+Gmelin.

A final word of ink advice from the Z+G ink specialists, don’t lay down ink on the overlap areas – move the artwork so the overlap is free of print and you’ll save yourself a headache in the long run. These areas will undergo significant distortion during the shrinkage process. If ink is applied to the overlap areas, it will also shrink with the sleeve. As a result, the ink in these areas may become distorted, causing alignment issues, color shifts, and other print defects. The artwork or text on the shrink sleeve is carefully designed to fit the container when it is in its shrunken state. Any ink laid down on the overlap areas can disrupt this design and negatively impact the overall appearance of the package.

Zeller+Gmelin is your knowledgeable ink partner, eager and ready to help you achieve shrink sleeve printing, expertly done. We hope this blog has provided a good starting point for controlling your production process for successful shrink applications. Want to learn more? Contact our team – we are happy to discuss our UV and LED inks for shrink applications, answer any questions you have and share our knowledge on Flexo print best practices for your unique application. We are here to serve you!

The post 3 Key Flexo Components for Successful Shrink Sleeve Printing first appeared on Zeller + Gmelin.

As LED curing systems gain wider acceptance in the Flexographic industry, the benefits of the systems create many compelling reasons to switch. Extended lamp life beyond 30,000 hours, instant on, “cool curing” with minimal heating and distortion of the substrate, reduced energy consumption, consistent depth of cure, no toxic mercury from the lamps and no ozone generation (and therefore no necessity for ventilation), are just a few significant benefits with LED flexo curing technology.

As more and more flexographic LED systems are installed, Zeller+Gmelin has formulated high quality LED flexo inks to help converters take advantage of the many benefits of this exciting new technology. Before “flipping the switch” on either ordering a new press configured with an LED curing system, or retrofitting an existing press with an LED system, it’s important to ask the right questions to ensure you’re purchasing the best system for your future.

Here are some common questions we receive from customers getting started with LED Flexo inks and answers from Zeller + Gmelin Ink Specialists to assist you in your journey into LED technology.

Frequently Asked Questions

Will an LED system really save money?

The short answer is yes. Though each manufacturer has unique cost saving benefits innovated into their LED curing systems, all LED systems are known for achieving big savings in energy consumption. LED curing systems are incredibly more energy efficient and can help converters save money on energy bills and other soft benefits throughout the plant. Also the cost savings attributed to less maintenance, consistent curing, and instant on-off technology keeps your equipment up and running, reducing downtime and increasing profitability.

What is the curing quality of LED compared to UV?

From our perspective, one of the biggest benefits of LED is the consistency of cure, compared to a conventional mercury UV system. With conventional UV curing systems, curing consistency can decline over the life of the bulbs and regular maintenance is required: including cleaning the reflectors, bulb replacement after around 1000 hours (considering the bulb output will continuously decline over the life of the bulb), and maintenance of the other mechanical components of the system.

Alternatively, an LED system offers steady, consistent curing power output for the life of the system, without the steady decline in curing power. With LED curing technology, your ink curing stays consistent – especially important if you’re running low migration work!

Can I run LED Flexo inks on my conventional UV presses too?

Maybe you’re still using UV curing systems throughout your operations and you’re hesitant to make the switch to LED only to end up with two inventories of inks: LED-curable and UV-curable.  At Zeller + Gmelin, we adapt our inks to the needs of the market and formulated the 17 Series LED Flexo Inks for “dual cure”, meaning they will cure under both LED and conventional mercury curing systems.

If you’re running operations with both LED and UV curing systems, you only need one inventory of Zeller + Gmelin LED Flexo inks to use throughout your operations.  Just be aware that the reverse is not true – UV flexo inks designed for mercury systems will not cure under an LED system.

What are the benefits of LED curing systems, not available on UV systems?

Though LED and UV curing technologies ultimately both cure ink effectively, LED systems have multiple benefits unique to its low heat and energy-efficient characteristics. To begin, UV curing systems have short-wavelength lamps that convert oxygen into ozone, which can irritate your operators and will need to be ventilated – while LED systems create no ozone to vent. LED is also known for its much cooler operations – while LED systems will create some heat in the web, it’s nothing like the heat generated by a conventional mercury system, since those bulbs also emit infrared wavelengths. This also translates into quieter operations.

Additionally, LED systems are instant on and off, with no warm up or cool down time necessary. These benefits make LED systems an excellent option for curing many colors, especially heavy opaque whites, at higher run speeds.

What are the limitations of LED systems?

LED curing has limitations for surface printed clears, like coatings and varnishes. LED is great for “buried” clears, like lamination and cold foil adhesives, but clear surface coatings don’t develop a good level of surface cure with LED. Many of our customers install LED on all but the last unit, where they keep a mercury bulb to cure coatings.

Why are LED inks more expensive than UV inks?

LED Flexo inks, at least right now, cost a little more than comparable conventional UV flexo inks. This is primarily due to the relative “newness” of LED inks in general, which limits available raw materials for formulation. Just like cell phones, computers, and any other new technology, the costs start out higher until that technology becomes more widespread. We expect the cost of LED inks to continue to come down as the technology is adopted into the industry on a wider basis.

Making the Switch to LED Flexo

LED curing systems for narrow web printing are still evolving. Like any other new technology, your decision needs to balance your current need with where the technology has advanced to today and where it is expected to be in the next 6 months. Now that you better understand the benefits and limitations of an LED curing system, you may be ready to take the next step.

At Zeller + Gmelin we are here to assist you through every important ink-related decision. We can put you in touch with our LED curing system partners, and even introduce you to customers who have embraced LED curing, so you can speak firsthand with them to inform your decision.

Talk to your Zeller + Gmelin Account Manager today to discuss your operations and see if it makes sense to step into the world of LED curing systems and inks.

The post Getting Started with LED Flexo Inks: Frequently Asked Questions first appeared on Zeller + Gmelin.

Author: Ed Dedman, Zeller+Gmelin Flexo Product Manager

This article was first posted by the Flexographic Technical Association

Ink—that magical, mystical fluid—delights designers, annoys accountants, inspires inkies and P-O’s press operators! We use it in flexo presses every day, all day, across the country and around the world, yet so many people don’t understand how ink really works, what it can and can’t do, and how to use it best to maximize productivity in the pressroom.

FTA asked me to do an FTA Member Webinar on the basics of flexographic inks. We had good attendance, a lot of questions and a lot of follow-up communications. In this article, I’ll try to recap the information that was conveyed in the webinar, along with a little bit of further detail about some of the topics that were of most interest to folks. I’ll cover the basics of all three common flexographic ink chemistries—water based, solvent based and energy curable. We’ll explore the basic ingredients used in each chemistry, how they work in each type of ink and how they perform their functions on press. You’ll learn how ink manufacturers make these inks in both large bulk form and in small batches. Also covered will be typical quality control (QC) checks used, and the tools and equipment required to perform those checks, both in the QC lab and in your pressroom. Finally, we’ll cover some on-press variables that can affect ink performance and some basic suggestions for troubleshooting common ink problems.

Before we dig too deep, let me just offer three “qualifiers”:

As previously mentioned, flexographic inks are divided into three main categories. Water-based inks are used on wide web flexo presses for applications like paper packaging, overwraps, bags, etc., and in narrow web flexo for products like pressure-sensitive labels, tags, envelopes and the like. Solvent-based inks are used primarily in wide web applications like film packaging, overwraps, bags, pouches, etc.; they see very little use in narrow web, but are occasionally the ink of choice for adhesives, coatings, etc. And lastly, the category of energy-curable inks covers three main energy curing methods—ultraviolet (UV), light-emitting diode (LED) and electron beam (EB). Both UV and LED are in widespread use in the narrow web portion of the flexo industry, with EB used to a much lower degree in both wide and narrow web.

Basic Ingredients & How They Work

The main components in any water-based ink system are the following:

For solvent-based systems, the components are similar, but slightly different:

For energy-curable inks, the components are once again similar, with some significant differences:

In summary, the basic ingredients of each ink chemistry vary mainly in the type of resin system used, and the method of drying or curing used. Each chemistry has its strengths and weaknesses, because each is utilized for different print applications, based on the suitability for the end product. Some colorants work better in one chemistry versus another, due to their relative ability to “wet out” those pigments.

Both water-based and solvent-based inks dry by evaporation, absorption or a combination of both. Energy-curable systems dry by being “cured” after exposure to energy; in the case of UV and LED inks, that energy is light, where for EB inks the energy is a stream of electrons.

Manufacturing Larger Batches

Most ink manufacturers make large batches of common ink formulas, in order to maximize efficiency and manage costs. Most colorants must be “ground” to wet out their surface area in order to be effectively “carried” by the resin vehicle system through the printing process. Some sort of manufacturing method/device must be used that imparts physical energy to the colorant mixture, in order to break it up into smaller particles. Ink companies use machines like bead mills, shot mills, three roll mills and the like for this purpose.

The inks are then typically strained or filtered afterward to capture any large particles. The formula is often completed by the addition of other ingredients needed to make a “finished” ink that is ready for press.

For smaller batch sizes or for mixtures of different colored inks, blending is typically used at an ink company branch facility or a customer inkroom. Blending takes much less physical energy, and can be accomplished by using small mixers, stirrers or through hand mixing with a drill/blade combination, or even a stir stick.

Most ink manufacturers use stringent quality control methods and equipment to make sure their inks are on spec for their various attributes—such as measuring viscosity, seen here—as part of the internal manufacturing process.

Quality Control at the Manufacturer & Print Facility

Most ink manufacturers use stringent quality control methods and equipment to make sure their inks are on spec for their various attributes—color, strength, viscosity, adhesion, gloss—as part of the internal manufacturing process. Tools like a viscometer, grind gauge, proofer, spectrophotometer, gloss meter, pH meter, rub tester and COF tester are used during the development process, as well as during manufacture. Other tools are available for the ink manufacturer as needed, depending on the properties desired in the finished product.

Some of these same QC tools can often be used at the print facility, but some favored by ink manufacturers are cost prohibitive for a printer’s pressroom or inkroom. Typically, the printer can effectively monitor ink condition and suitability for use with tools like a Zahn cup for viscosity measurement for water-based and solvent-based inks (but not for energy-curable inks—these inks are too viscous for using a cup method), a pH meter for water-based inks, a hand proofer, a spectrodensitometer, and possibly a gloss meter, rub tester and COF tester for QC of the finished printed material.

On-Press Variables Affecting Ink Performance

It would take a completely separate webinar and accompanying article to adequately cover the on-press variables that can affect ink performance. Here are a few of the things a printer should be aware of that can affect how an ink performs on press and as a printed product:

Basic Ink Troubleshooting

A few basic tips: In general, when you are troubleshooting, make one change at a time. Always follow your ink supplier’s recommendations. For specific problems, contact your supplier! And always check the basics first—don’t make major changes without confirming you have the right ink for the right job, using the right conditions.

Specific to ink adjustments—in general terms:

For color adjustments:

No matter which type of ink chemistry you use, the bottom line is this: Take care of your ink, and it will take care of you. Treat the ink as a fundamental part of your printing process. Control its condition as you would any other aspect of the pressrun—equipment and materials.

The post The Basics of Flexo Ink Chemistries, Manufacturing & On-Press Maintenance first appeared on Zeller + Gmelin.