Do you have a favorite glass or cup you always reach for in the cabinet? Have you ever considered how many washes it has been through? Yet despite having it for years, the design remains just as it did the day you brought it home. Now consider a glass or cup you brought home from an event and ran through the dishwasher once and the design melted off.
What caused the second piece of drinkware to have such a short lifespan, and what contributed to the first piece lasting so long? Flame treatment for adhesion can make all the difference when it comes to a long and vibrant lifespan of digitally printed ink.
Two Main Reasons for Flame Treatment
Flame treatment for adhesion serves two purposes: it prepares the substrate surface so ink bonds properly, and it removes contaminants that would otherwise weaken that bond.
Flame treatment is necessary for adhesion, durability, and abrasion resistance. Just because you can physically print on any drinkware of choice doesn’t mean the ink will stick. Therefore, you take a glass that ink doesn’t stick to, flame treat it, and now ink will adhere when printed on.
Flame treatment also serves another important purpose: during the flame treatment process, oils, dust and other contaminants found on the surface of the substrate are burned off, allowing for a cleaner seal.
What is Flame Treatment?
Flame treatment for adhesion is the process of taking a gas flame to the surface of a substrate to change the surface tension. Some types of glass, plastic, and polymers consist of long non-polar molecules. By quickly taking a gas flame to the surface of these materials, one can break down molecular chains and add polar functional groups.
For example, popular substrates such as polypropylene and polyethylene have low surface tension, so a flame treatment can alter and increase the surface tension. Flame treatment is one of several pretreatment methods for glass that Inkcups supports, alongside others like primer wipes and MagiCoat™ pretreatment.
The Flame Itself
The flame must be blue to begin the flame treatment. It has two parts; the primary, which is the light blue inner cone, and the secondary, which is the dark blue outer cone. The blue color of the flame means that the ratio of fuel to air is gas lean, which in turn is oxidizing. The surface tension of your substrate will only be correctly manipulated if the flame is oxidizing.
The flame is applied to the surface of the substrate quickly, evenly, and in motion thus preventing the substrate itself from melting.
Inkcups Flame Treatment Solutions
The dedicated flame treatment machine provided by Inkcups is the MagiCoat Pre-Treatment System.
This system begins with a flame treatment process, plus the addition of the fine mist spraying system for spray-on primers. An operator individually loads each piece of drinkware onto eight palettes. Each palette rotates 360-degrees at each stop, one of which is at the flame, another of which is at the MagiCoat primer station.
Upon completion of the full rotation around the MagiCoat machine, an operator must then manually remove each piece of drinkware. The MagiCoat system is specifically for glass drinkware, thus the need for manual retrieval due to the breakable nature of the substrate.
Do all Substrates need to be Flame-Treated?
Not all substrates will need to be flame-treated. This decision comes down to a few factors:
One common misconception when it comes to UV printing is that there is a universal ink for all substrates. This is completely false. Not one ink can stick to all substrates. For a closer look at how ink choice, primer, and pretreatment work together, see our guide to improving UV ink adhesion.
Depending on the inkjet primer, some will assist with adhesion without the need for applying flame. For example, the XF Primer for Powder Coated Vessels adheres to powder coated substrates without flame. This primer was designed for this product and therefore does not need additional help to get ink to stick.
Adhesion Requirements
Adhesion requirements are set by how the finished piece will be used, tested, and washed. There are also instances where adhesion requirements negate the need for flame-treatment or will encourage flame-treatment. Some items that are more for promotion rather than retail may have different requirements, and for glass drinkware, those requirements are typically confirmed with the ASTM adhesion tests for glass.
Are you ready to add a flame treatment process to your business? Contact the sales representative in your area today.
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