Comment
CHRIS MCKENZIE, technical director at TOLAG, which he relaunched earlier this year, takes a close look at surface treatment and ink adhesion of a beverage can, scratching the ink with car keys (fingernail will do, too), and gives his verdict.
A sticking point
For industry professionals, it comes with the territory As we walk through our local shops, those of us who are in the industry are drawn to the aluminium beverage selection and often get worried looks from shop workers and concerned shoppers. They’re probably thinking about why we’re holding that can for so long and why we’re reading all the small print. Why are we looking at the bottom of that can and scratching it with our car keys? “Quickly, call security and get them cable tied,” is probably what’s crossing their minds.
A close up of a piece of white material Yes, it sounds funny, but you all know it’s true. Talking to another industry supplier recently, I mention this anomaly and how strange it’s that on flights to Denver, Shanghai, Germany, etc., while exhibitions are on, we often see flight attendants grappling with a man in seat 12C who refuses to let her take the empty beer can for disposal.
One of the items most checked, using that car key again, is the adhesion of the ink to the can in general, and most importantly, the necked area as the most stringent test of ink laydown. This adhesion is affected by a plethora of problems with the most common being overtreatment with stage 4 in the washer causing phosphate buildup that the ink can’t lay down on. The presence of silicon contaminants can cause the ink to dewet from the substrate in many cases and not adhere in some.
Those breweries globally that didn’t embrace this for a multitude of reasons, but we’re to wonder if this is a question of not moving liability from the can supplier to the end user. This is a simple fix as well as eliminating some major acids that impact the downstream wastewater treatment, the elimination of this process makes the sustainability of the can superior.
More recently the birth of the craft beer market has been wondrous for the industry with problems occurring pre-Covid of low volume needs, a problem that came to a head during the pandemic with the market in standard beer and beverage making the largest jump in demand since the 1970s. Many craft brewers went to the wall because they couldn’t get packaging in any shape or form, and any tap drawn produce being flushed down the drain because of Covid restrictions.
apparent that the UV based inks would not pass the age-old adhesion tests, in fact not even the car key test
The use of modern digital UV cured inks are particularly troublesome with true adhesion not being capable to be directly applied to the substrate, a key is needed to hold the ink by altering the surface energy of the metal. To date this can only be done with a compatible base coat, which negates that shine through we’ve become so used to, and the fillers have embraced over the past three decades, notwithstanding the elimination of a major cost impact.
The test throughout the past decades, as dictated by the fillers, has become more and more stringent with cans being heated in a bath of chemically driven harshness designed to emulate the worst conditions in any water medium used in the brewers super-heated pasteurisation process. The US brewing industry from the start has been clever and ensured that the pH and contamination levels of the pasteurisation process is controlled and, as such, there was no need for treatment stage to be added giving lower cost per thousand impacts as well as superior adhesion capabilities.
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metalpackager.com It soon became
Digital printing appeared to be the saviour with can plants managing to supply virgin cans without labels, initially shrink wrapped at higher cost with now a possible low volume capability print. It soon became apparent that the UV based inks would not pass the age-old adhesion tests, in fact not even the car key test. More recently, we’ve seen failure with just a fingernail test.
The base coat mentioned earlier wasn’t the answer because modern can plants no longer have the process in their plants and those older plants that delved into their storage system and reactivated the trusty basecoater quickly found that 36 hours was
as long as this coating was acceptable before curing and having the same surface energy and thus problems as the substrate. Craft brewers seemed not to be daunted by this adhesion failure, neither were the excited beer drinkers who were only interested in what was in the can but did lovingly admire the striking graphics of the latest offering on the shelf.
This brings us to the question that’s often mooted by the average consumer: are these tests overkill and have we become slaves to an overzealous marketing team, control of pasteurisers, lack of concern about adhesion of inks unless they’re jumping off the can?
The choice of steel versus aluminium isn’t essential to the average consumer, just to the suppliers in the plane on the way to exhibitions. Let’s not adhere to too many tests and focus on costs, beauty and taste.
Chris McKenzie can be contacted at
chrismckenzie@tolag.com.au.
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