What Are Aluminum Bottle Caps Made of

The core material for aluminum bottle caps is specially processed aluminum sheet, not ordinary pure aluminum. Pure aluminum is soft and easily deformed; using it directly to make bottle caps is neither durable nor able to meet practical requirements such as sealing and corrosion resistance. Most qualified aluminum bottle caps on the market rely on three types of finely processed aluminum sheets: DOS oil lubricated aluminum sheet, color-coated aluminum sheet, and color-printed aluminum sheet.

Before manufacturing the bottle caps, a layer of food-grade special lubricating oil is pre-coated onto the surface of the aluminum sheet. This oil film plays a crucial role. On one hand, it reduces friction between the aluminum sheet and the mold during stamping and forming, preventing scratches and deformation on the bottle cap surface, ensuring precise dimensions and smooth edges for each cap.

On the other hand, this food-grade oil also forms a barrier when the bottle cap comes into contact with the beverage, preventing the aluminum from reacting with the acidic or alkaline components in the beverage, protecting both the taste and drinking safety. It can be said that DOS-coated aluminum sheets are a prerequisite for "good" aluminum bottle caps.

Color-coated aluminum sheets are made by pre-coating an aluminum sheet with a layer of colored paint. This paint not only gives the bottle cap a vibrant base color, such as the common cola red or Sprite green, but also provides some protection against oxidation and scratches.

The paint undergoes rigorous screening and must meet food contact standards. Even with prolonged exposure to air or humid environments, it will not fade or peel.

For bottle caps that need to display complex content such as brand logos, product information, or QR codes, color-printed aluminum sheets are the best choice. Using high-precision printing technology, the design is directly printed onto the aluminum sheet surface, resulting in high clarity and excellent color reproduction, allowing consumers to easily identify the brand.

Some high-end beverage bottle caps combine color coating and color printing processes—first applying a base color to the aluminum sheet, then printing the design on top, creating a more layered and visually attracting design.

It's worth noting that both color coating and color printing paints and inks must pass food-grade safety testing to ensure they do not release harmful substances under different conditions, such as high and low temperatures.

Some might ask, why the aluminum closure sheet is used, not other bottle cap materials? This is closely related to aluminum's properties. Aluminum has a low density, making bottle caps lightweight and not adding to the overall weight of the packaging; its good ductility allows it to be easily molded into various shapes through stamping, resulting in a stronger seal against the bottle opening.

Furthermore, aluminum's cost is relatively controllable, and its high recyclability aligns with the current trend of environmentally friendly packaging. Combined with a series of refined processes such as DOS coating, color coating, and color printing, aluminum becomes the "golden material" for making bottle caps.

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