|
|
|
Glass is
Glass, Isn't it?
|
|
|
The glass decorating market is unique and challenging, in part because of the wide variety of applications where glass is used, but also because of variations in the substrate.
When you consider decorating, one would think glass is a constant in the variable- filled world of screen printing. Letıs look at glass containers though, and see if this theory stands up.
Common uses for glass containers include foods, beverages, and cosmetics, as well as drinking ware. Many glass containers are coated to protect them from scratching during handling. These coatings can be polyethylene emulsions, or they can be lubricants such as AP5, which is a liquid fatty acid.
Polyethylene emulsions, such as Duracote from Sun Chemical are the most common and offer the highest degree of protection. Food, beer and soft drink containers typically use this type of coating. Hereıs how they are applied: Glass containers may be passed through a lehr oven after they are manufactured. This process, known as annealing, removes stress from the glass and adds strength. A tin oxide primer is spray applied as the containers exit the lehr. This is commonly known as hot end treatment. The polyethylene emulsion is spray applied over the primer. Without the primer, the emulsion does not have sufficient adhesion to the glass to offer protection. The emulsion is usually applied at 250oF (give or take a little), and is referred to as cold end treatment. The recommended amount of coating applied varies depending on end-use requirements. More emulsion results in more protection. For example, beer bottles usually require .016 mg/square inch or greater, but food containers only require .005-.010 mg/square inch. As an alternative to emulsions, lubricants such as AP5 may be used. AP5 is used for applications like wine and food containers, where the containers tend to be handled with more care. Like the PE emulsions, AP5 is spray applied, typically at 200oF or less. Because of the low temperature, this may also be referred to as cold end treatment.
By contrast, cosmetic bottles usually do not require protective coatings primarily because of the way they are handled. In the glass market, the advantages of UV decorating continue to be recognized. As one might imagine, the aforementioned protective coatings can have a major impact on ink adhesion, especially when looking at UV curable inks. To achieve desired results with UV inks, it is important to know the type of coating, if any, that will be decorated.
It is also important to understand end-use requirements for the decorated containers. For example, cosmetic containers need resistance to alcohol and essential oils, while beer and soft drink containers need resistance to water, and drinking ware needs resistance to dishwashing.
As ink manufacturers, knowing this information helps us make proper recommendations for pre-treatment, catalysts, and curing conditions. Our UV ink for glass, Crystal GLS, can be used for a variety of applications, depending on end-use requirements. Maximum water, chemical, and adhesion properties are achieved with a catalyst. Using Crystal as an alternative to frit helps printers realize the benefits of UV curing such as energy savings, space savings, and enhanced print quality - just to name a few.
|
|
