In surface finishing industry, sometimes we need to give metallic treatment for different materials. Normally we use vacuum metallization or electro plating directly, but if we need to apply a specific design to surface, these solutions are not perfect and we need to source another way called “gold stamping“.
Gold stamping overview
Gold stamping or sometimes known as hot stamping. The process uses the principle of hot pressure transfer to transfer the anodized aluminum layer onto substrate surface to form a special metallic effect. Becase the main material used for stamping is anodized aluminum foil, gold stamping is also called anodized aluminum hot stamping. The most commonly used in printing industry is to hot stamp electrochemical aluminum foil on paper, which is called gold stamping. It is a general term for a process but does not mean that what is stamped is gold color. There are many kinds of stamping materials including gold, silver, laser gold, laser silver, black, red, green etc.
Anodized aluminum stamping foil is generally composed of 5 layers:
Layer 1 is the base which is composed of biaxially oriented polyester film, usually PET. It is the intermediary that plays the role of connection and support in anodized aluminum.
Layer 2 is the peel layer. Its main component is silicone resin, which will automatically melt and fall off when heated. Aluminum coating layer can be easily transfered.
The third layer is the coloring layer. It is the main body that forms the colored anodized aluminum (silver anodized aluminum does not have this layer). It is usually made of heat-resistant transparent synthetic resin (such as maleic anhydride resin) and dye. It is dissolved in an organic solvent and then directly coated on the peeling layer surface.
The fourth layer is the aluminum plating layer. It is made of aluminum metal that vaporizes under high temperature and vacuum conditions, and evenly adheres to the surface of the colored layer, which plays a role in increasing the metallic luster.
The last layer is the hot melt adhesive layer. In electrochemical aluminum hot stamping, it is heated to melt and adhere to the surface of the printing material, which plays a role in fixing the aluminum layer.
The application process is this: adhesive layer in the gold foil or silver foil is activated by heat and pressure, and the release layer melts, attaching the machine hot foil to the medium. The machine used for this hot foiling process is called a hot foil stamper /hot foil stamping machine
How to select the suitable stamping foil?
When we select anodized aluminum, not just about the color, the most important thing is to choose different types of anodized aluminum according to our own uses. Because some models of various anodized aluminum are suitable for hot stamping of plastic films and soft plastic products. Some are suitable for hot stamping on leather, wood, and oilcloth, some are suitable on dark ink layers, and some are suitable on light ink layers.
The models of anodized aluminum produced by different manufacturers for the same purpose are not necessarily the same, and the hot stamping temperatures of the same model of anodized aluminum are not necessarily the same. Therefore, when purchasing anodized aluminum, we must first understand the model classification of the anodized aluminum manufacturer. The corresponding anodized aluminum model and color should be selected according to the performance and use of the product, the nature of the hot stamping material and the machine speed.
Differences from vacuum metallization
Different application method – hot stamping relies on hot stamping equipment to adhere under pressure and temperature, and vacuum metallization relies on a combination of vacuum machine and spraying technology.
The principles are different – hot stamping is when electrochemical aluminum is heated and melts to adhere to the surface of the printing material, while vacuum metallization is by aluminum vaporization and deposits on product surface.
They belong to different industries – hot stamping belongs to the printing industry, vacuum metallization belongs to the painting industry, gold stamping focuses on products with small size and regular surfaces, while vacuum electroplating has no restrictions
