Is Your Glass Labeling System Letting You Down? Here Are the Keys to Success
While metal and plastic containers are entering new markets, there are still many cases where glass containers and glass jars are the best solution. Glass is a great choice for both alcoholic and non-alcoholic beverages because it’s non-reactive, completely non-permeable, and can handle pressure from carbonation. If you’re packaging highly reactive chemicals, glass is often the safest way to transport them. Glass is also available in a range of colors that block UV, visible, and infrared light for added protection.
However, glass labeling can be difficult. Like any container, glass presents unique challenges caused by complicated shapes, product handling, and manufacturing inconsistencies. Here’s how you can work around these problems to get consistent, eye-catching glass bottle labeling.
What Are My Options for Glass Bottle Labels?
Type I, II, and III glass bottles may use different materials and manufacturing processes but have the same adhesive compatibility. When you choose a glass labeling method, the main things to consider are scale and cost.
Applied Ceramic Labeling or Silk Screen Printing
Applied Ceramic Labeling (ACL), also known as silk screen printing, applies ink directly to the bottle. Heating the ink fixes it to the bottle surface. This process can cover the entire bottle, but it’s limited to three colors.
Heat Transfer
Unlike ACL, heat transfer labeling offers high-quality, full-color prints, but the label adhesion process is complicated. The bottle and label have to be preheated to ensure full ink transfer, then the bottle is heated again to fix the ink to the surface. Since both heat transfer and ACL require specialized equipment, they’re handled by the bottle producer, not the product manufacturer.
Shrink Sleeves
Shrink sleeves made from PVC or PETG contract around the bottle when exposed to direct heat or steam. Designs have to take this shrinking into account to prevent graphics and text from warping. While in-house applications are possible using tunnels, this equipment is expensive and only used in high-volume applications.
Cut and Stack Labeling
Cut and stack labeling applies glue to the back of the label during application. While this is inexpensive, the limited adhesion makes labels more susceptible to damage. These glues don’t hold up to high temperatures. If you use heat to cook or pasteurize your products, the product label must be applied after the bottle cools.
Pressure-Sensitive Labeling
Pressure-sensitive labeling uses labels that come with an adhesive applied across the entire back surface of the label materials. This method allows users to select from a wide range of label stock, adhesive finishes, and inks. This flexibility and increased adhesive contact offer better durability than cut and stack labeling. It’s also more affordable than ACL, heat transfer, and shrink sleeves for products with small production runs. Pressure-sensitive labels that support hot filling are also available. For craft bottling applications, this is by far the most practical labeling method.
Want to show off your product? You can get the clear look of ACL with pressure-sensitive labeling by using clear polypropylene films. This requires upgraded label sensors on your labeling machine. Instead of using light, these sensors use electrical resistance, measuring the thickness of the web so the machine can tell the difference between barebacking and backing covered by a label. Machines with these sensors work with both clear and opaque labels.
Decorative Manufacturing and its Effect on Label Application
If you’re just starting out, it makes sense to buy an off-the-shelf bottle design. However, if you want your brand to stand out, it may be worth investing in custom bottles. Most bottles start with a standard design, modifying the surface to create a unique shape.
Acid etching uses hydrofluoric acid to erode the glass, leaving behind a frosted surface. Although historically used for fine glassware, it’s simple enough to use mass-produced bottles. The entire bottle up to the finish, the bottle’s opening, can be etched. Alternatively, etching can be limited to small sections, creating intricate patterns. All labeling methods work on this surface.
Embossing molds the bottle during production into raised lettering or images, interfering with the functionality of all labeling methods. It’s common for brands to add their logo to the neck or shoulder of the bottle, leaving the body open for product-specific labeling. When you’re planning your custom label system, remember that you may need to orient embossed bottles, even if they’re round. This ensures the embossed design lines up with the principal display panel.
Debossing presses designs into the bottle surface during production. Colors can be added to the debossed area, creating designs that are both visual and tactile. Like embossing, this interferes with label application. Debossing is a complicated process, requiring heating and cooling to fix the design and remove internal stress in the glass. It’s common for debossed bottles to be coated with a thin layer of polyethylene to reduce surface friction so bottles don’t damage each other as they pass through production lines. This must be taken into account when selecting compatible adhesives for your labels.
Estimating Label Sizes Based on Bottle Shape
If you’re starting with a common design, like the Industry Standard Bottle (ISB) used by craft beer and soda manufacturers, there are plenty of off-the-shelf label options. Otherwise, you need to do some measuring to match your label shapes to your bottles. Our vertical trunnion roller labeler supports every common label type, including neck and tamper-proof labels. If you just want to label the body, we have a simpler labeler that supports single-wrap labels, as well as front and back labels.
Most glass bottles are made with two-piece molds. Since the mold unfolds from the bottle, the bottle’s sides can be flat. This minimizes skew, which is a constant problem for the sloped sides resulting from blow molds used in plastic bottle production. However, low-cost glass manufacturing results in greater surface inconsistencies than plastic containers. To compensate for this, allow ⅛ to ¼ inches of space along edges for overrun.
While shrink sleeves conform to any bottle shape, all other labeling methods require flat surfaces. The body of the bottle is almost always flat. Some necks are flat, while others have a slight curve that causes wrinkles, flagging, and skewing of pressure-sensitive labels. To check the shape of a surface, hold a flat object like a ruler or pencil against the surface. If you can see gaps at the edges, the surface is curved. Many glass beer and soda bottles also have raised shoulders on the top and bottom of the body. Body labels must be applied between these raised areas.
To estimate the maximum length of a label, use a fabric ruler or measure the bottle’s width and multiply by pi. On angled surfaces, like the neck, you need to measure the top and bottom of the area where you want to apply the label. Your label designer can use these measurements to create a curved label with skewed text and graphics that look flat once applied.
Get Accurate, Reliable, and Efficient Bottle Label Application
CTM Labeling Systems makes a wide range of pressure-sensitive labeling equipment, including machines designed specifically for glass labeling. If you’re looking for an effective way to label your glass containers, contact us to get in touch with your local distributor. They work with you to create a custom labeling system that fits your product needs.
