How to Read the Markings on the Bottom of Glass Packaging
Have you ever turned a glass bottle or jar upside down and noticed various numbers, codes, symbols, and marks? These seemingly random markings actually hold valuable information about the glass material. In this guide, we'll break down what these markings typically mean, giving you a deeper understanding of the glass you're using in your products.
Manufacturer's Mark or Logo
This is typically a small logo or symbol, often accompanied by letters, that identifies the company responsible for the mold and the glass production.
For instance, Glassnow bottles and jars display a logo with the letters “GN,” representing the company's commitment to high-quality products and serving as a mark of excellence that we proudly stand behind.
Mold Code
Mold codes identify the specific mold used in producing a glass item and can appear as alphanumeric characters, digital codes, or dot codes.
Digital and dot codes are often used for automated sorting processes at the cold end (near completion of production), while alphanumeric codes typically require manual sorting. These codes are usually located near the edge or center of the bottle's bottom.
Digital codes might include barcodes, QR codes, or other machine-readable marks, which can be etched or applied to glass using various technologies. In mass production, where multiple molds create identical items, mold codes are essential for tracing defects back to the specific mold that caused them.
Recycling Symbol (Mobius Loop)
You're likely familiar with this symbol as one of the most common recycling codes found on glass packaging. It indicates that the product is recyclable and may sometimes include a percentage in the center, showing the proportion of the product made from recycled materials.
Glass Material Codes (GL)
These codes are part of a classification system that identifies different types of glass based on their composition and intended use:
• GL 70 - Clear Glass: Typically used for clear glass containers, such as bottles and jars.
• GL 71 - Green Glass: Found in green-tinted glass, often used for wine and beer bottles.
• GL 72 - Brown Glass: Commonly seen on amber-colored glass, frequently used for beer bottles and certain food jars.
Capacity Markings
Numbers like "500 ml" or "16 oz" indicate the volume that the glass container can hold. This information is usually found on the bottom of glass bottles or jars and may specify the nominal volume, the fill level, or both.
Patent or Design Numbers
Occasionally, you might notice a long number on the glass, which corresponds to a patent or design registration. This number provides legal information about the intellectual property rights associated with the design or function of the glass item.
Understanding these markings can offer valuable insights into the glassware you use, whether for manufacturing purposes or personal use. Glass containers, packaging, and accessories come with many nuances, so feel free to explore our blog or reach out to one of our experts if you have any questions—we're here to share our knowledge and help you navigate the details.