Window patching is a technique where a window film is added on a carton or any other product packaging serving a dual purpose.
It teases the product by making some of it visible and can also it prevent food from coming into contact with the carton. The decision to add a window film patch will naturally, depend on the nature of the product.
Exterior look is the next priority as the quality and integrity of the consumable product will assume higher priority.
Window Patch Films
Aside from paperboard, plastic is one of the most used material for packaging particularly polyethylene terephthalate (PET) and polyvinyl chloride (PVC) plastics.
PET film is molded into the required shape followed by a drying process for enhanced resistance. The strong reinforcement provided by PET makes it tamper-proof and provides good resistance to the elements. Besides food packages, it is also used for beverage bottles.
PET plastic is lightweight, which in turn may be prone to scratches, but yet sturdy enough to combat exterior pressure and helps safeguard the contents within. It is also a safe option for storing foods, as well as a popular choice for electronics, retail and other consumer products.
PVC film offers a more durable exterior, and a superior scratch and dent resistant surface. It is extremely resistant to tampering and natural elements. However, exposure to UV rays may result in degradation over time causing odor and water ripple. It is a less environmentally friendly option and isn’t a suitable choice for food packaging.
- Polypropylene is the most commonly used film to pack candy, snacks and baked
- Glassine is used for high grease products
- Polyethylene is used for frozen food products
- Polyolefin is a shrink film used for pizza and boxed candies
- Foil lamination is ideal for light and air sensitive food products
The Window Patching Process
At the heart of the process is a window patching machine. It could be one from a leading manufacturer Heiber + Schröder or a specialist window patching machine manufacturer Kohmann.
The machine will apply windows from a reel using a specific plastic film (PET, PVC etc…). Packaging cartons are first fed through the reel at a rate of approximately 375m/min and through the process, films are added into the paper packaging through electromagnetic energy.
Depending on the type of machine being used for the window patching, typically, the plastic film will stick instantly to the packaging material without any drying time. It is ready to package instantly once it is released from the machine.