UV printing has revolutionized how brands and designers approach glassware decoration and customization. From high-end packaging to drinkware and décor, digital printing on glass offers unmatched color, speed, and quality. In this guide, we’ll explore different types of glass, surface prep, and compare UV glass printing to other decoration methods.
While the glass we use today is the same or a variation of the “liquid sand” invented many years ago, glass decoration techniques have evolved over time with advances in technology. Although it’s a naturally occurring substance, glass was first produced by humans accidentally in the form of beads in the mid-third millennium BC, and has been the top drinkware choice ever since. Among the reasons why:
Glass is primarily made from silica (sand), combined with other raw materials to enhance its properties. The three most common types of glass are soda lime, borosilicate and tempered.
1. Soda Lime:
A mixture of soda lime and sand, this is the most common type of glass, accounting for about 90% of glass products in the market. It typically makes window panes (flat glass) and containers and jars for food, beverage bottles, plates and bowls, and even mirrors (with a reflective surface added).
2. Borosilicate:
Borosilicate is another type of glass made up of soda lime, sand and boron. This type of glass has excellent heat resistance so items that are constantly sitting over a fire or in an oven will not melt or crack. Items that are borosilicate glass range from test tubes or beakers to Pyrex.
3. Tempered:
Tempered glass is unique in that when broken, it shatters without making shards. Certain countries require establishments to use this type of glass as a safety precaution. Some common applications include vehicle windows, shower doors, screen protectors and even bullet proof glass.
There are two popular methods of coating that manufacturers will apply either before and/or after the annealing process (the slow cooling of the glass) to ensure the glassware is protected. The two methods are hot end coating and cold end coating.
Hot End Coating
Hot end coating is used on all bottles including wine, soda, spirit and even beer bottles before the annealing process. Once the glass is formed, a thin tin-chloride film is applied onto the glass making the surface more resistant to breakage. This coating is sprayed onto the inside and outside of the bottle. Hot end coating protects consumers from the glass shattering, which may occur because of a buildup of pressure due to carbonation.
Cold End Coating
For all other types of glass, manufacturers use a cold end coat to protect items from scratching and scuffing during shipping. This type of coating is either a spray or a vapor that is applied after the annealing process. There are multiple types of cold end coatings including water soluble, water insoluble, polyethylene or fatty acid types.
Before UV printing on glass, the surface must be properly pre-treated. Although glass is ideal for printing, partly due to its high surface free energy, it is susceptible to absorbing debris or other coatings which may inhibit adhesion. Common pre-treatment methods and products include:
These methods, used individually or in combination, are designed to improve ink adhesion and enhance print quality.
Inkcups also offers their own 3-part pre-treatment solution called MagiCoat®. MagiCoat® acts as the anchor after flame-treating. The water-based primer spray adds a new coating to the glass which promotes adhesion between the ink and glass. Unlike other methods on the market, MagiCoat® is completely safe to use and has been FDA approved. Learn more about the differences between a few pretreatment methods for glass.
Once the glass has been made and coated, many glassware companies will seek to decorate these items. The four most popular methods for decorating glass are using printed decals, pad printing, screen printing and UV printing.
Depending on the purpose of decorating glass and the volume of products, the method that is right for you will vary. Decals are popular for their easy application – the process is as simple as sticking the design onto the glass and applying pressure. Although most decals are manually applied, advances in technology such as heat transfer labeling machines have automated the process. This ensures the decals are uniform and adhered properly. Downsides to decal use include:
Pad printing allows you to choose up to 6 colors to print with. Depending on the artwork you wish to transfer, this may be limiting. However, many logos and designs use fewer colors, sometimes even just 1 or 2. The method you choose must align with your production and design goals.Other key benefits and considerations include:
Pad printing works best for low-mid sized volume production and promotional products with simple designs, such as logos that do not require a full wrap.
Screen printing can print up to 10 colors. Again, this may be limiting, but it depends on the production goals of the manufacturer. This process is the most time-consuming of the methods in terms of printing, but also when it comes to setting-up and cleaning the parts involved. To begin screen printing, you need inks, a squeegee, multiple screens, and an emulsion stencil. Screen printing is best for large designs without intricate detail, whereas pad printing works best for detailed designs on smaller products. However, there are options to buy finer screens with a higher mesh count for more detailed designs. Not only does screen printing require the most consumables, it also requires the most space. There must be enough room to properly wash the screen with water and screen wash solution, as well as the squeegee and stencils. Unlike pad printing, screen printing can achieve a 360-degree print, however, it will produce a seam.
Digital or inkjet printing utilizes UV ink to print full color onto cylindrical and tapered items. Once a graphic is created using the respective software, the UV printer will transfer a high resolution, picture-perfect image onto almost any surface at the click of a button. In this process, the machine jets the ink to the glass.
The benefits of digital UV printing include:
For companies looking to produce multi-color designs for large volume industrial use, inkjet printing is the optimal method of glass decoration.
After a graphic has been UV digitally printed onto the glass, some adhesion testing may be necessary. In order to assure that the ink has properly adhered to the glass, the edges are completely smooth, and the surface stays fully intact, these industry standard tests can be used:
To learn more and see them in action, check out our adhesion testing on glass blog post, and listen to our experts discuss ink adhesion testing methods for digital printing..
Glassware continues to be the material of choice, especially with the rise of plastic pollutants. Its inherent versatility makes it the perfect substrate to decorate and to personalize. Although it does provide a clear surface, it is important to note that printing directly onto glassware items will require pre-treatment as noted above.
Each decorating method has its own pros and cons, but these are specific to what each company would like to accomplish. In any case, when choosing which decorating method is right for your needs, always remember to note printing capabilities (number of colors, speed, etc.), the cost per print, and the pre-treatment methods needed.
For further questions, the Inkcups Team is always available to help.
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