On the downside, UV is three to 10 times more expensive than aqueous coating, which is more expensive than varnish. Another downside is that UV may also crack more easily when scored or folded due to the thickness and hardness of the coating.
Now here is the big deal: specially formulated coatings are required for each different digital output device. Not only that, but formulations may change throughout the year. For offset, UV compatible inks must be used.
Remember, with a UV coater you are dealing with a chemical process rather than a digital process. That is the major problem, according to our field research. Add to that the fact that different digital devices use different formulations of toner/fuser oil. This can cause a chemical imbalance between the coating, the environment (temperature), and the paper (substrate).
How’s that? Well, take water. When the temperature is low, the water turns to ice (low viscosity) and flows like a glacier. When it warms up, it flows like…well…water. It’s the same with coatings. The runniness will have an impact on flow, and you will apply more or less to the sheet. So, we’re back to a condition similar to balancing ink and water and holding your mouth right, and that is what comprises the vast majority of all headaches with the UV process – not equipment operations.
Other common issues include “orange peeling” or flaking away of the coating from the substrate (paper); curling; coating soaking into non-printed areas of the sheet, leaving it dull; and more. All of these issues almost always have to do with a combination of the coating, the substrate, and the environment.
Therefore, a good provider of coating is extremely important to you – perhaps more so than the equipment itself. Work with your provider in developing formulas for your digital output device. Know that you may have to use different coatings for offset and digital. Know that there are many variables and that a coating that is suitable today could give you problems tomorrow.
Expect change. Remain flexible and understand that your coating provider may have to fiddle with the formula several times until they get it right, and then may have to do it again later.
Cost of Coating
One other thing you need to know: vendors disagree on the cost of their coating material. Prices were quoted to us from $0.004 to $0.03 per 12x18" per side – again, that’s four mills to three cents. And even the higher amount received objections from some field reports as being too low.
At issue appears to be whether or not wastage is considered in the per piece calculation. Field reports tell us that while the cost for material to cover a 12x18" can be very low, there is a fair amount of wastage in the process (in some equipment more than others). That seems to be because setup and tear-down is about 20 minutes each way (some say faster).
And because most don’t leave the coating in the equipment overnight, that can add to the cost of direct materials. This causes many small press and digital printers to gang their coating production and run it only on certain days of the week.
So, make sure you understand the true cost of coating as well as wastage prior to buying the equipment. And if you would like guidance on how to price off-line UV coating, go to www.crouser.com and get our special report. Those subscribing to the Crouser Guides to Small Press or Digital Printing receive the report without additional cost.
So, that’s what I know about off-line UV coating. Hope it helps.