All the dealer/manufacturers of off-line UV coaters I talked with told me that 70-85% of the digital printers they know have UV coaters of some type. My survey, on the other hand, showed only 15% of us have that equipment and provide the service, while another 9% have someone else provide it for them (broker or sublet). So a full 76%, according to my panel, don’t have or provide the service. And that got me thinking…there are a lot of small-format offset and digital printers who don’t know that much about protective coatings. If you do, you’re excused until next month. Everyone else, please pay attention.
The purpose of a coating is to protect the printed piece from dirt, smudges, fingerprints, scratching, etc. Coating also provides scuff resistance. And, yes, it can improve the visual appeal of the piece by providing a glossier and smoother finish.
OK, enough of the Chamber of Commerce pitch: protective coating allows that postcard you did for your top account to arrive looking the way it looked when it was mailed. Printers who are aware that the postal service delivers a licking that keeps on ticking to printed pieces – and use that info to sell against unaware competitors – have an advantage.
Oh yes, the number two use of protective coatings is on business cards, for they are treated badly as well. Coming in third, about five lengths behind, are brochures and other types of sales literature.
The three common types of protective coating are varnish, aqueous coating, and UV coating.
• Varnishes were first in the industry as they are essentially inks without a pigment, or transparent ink. Their advantage is that varnishes are applied on a press, thus you can spot coat as easily as fully coating the sheet. The process is the same as printing spot color. You can also change the varnish from gloss to matte or dull, and thus change the mood of the piece.
The final advantage is that varnish is typically the least expensive of all the coatings available.
Drawbacks: varnish can be slow to dry unless you use a drier and, like ink, it is petroleum-based and could present some environmental issues, but it usually does not create issues in shops of our size.
• Aqueous Coating entered our world in the late 1970s. Aqueous is water-based, and thus does not cause emissions as varnish does. It does what varnishes do, but it’s also a polymer (basically, plastic), so some prefer this type of coating.
A quick dry formula was developed in the 1980s, so there’s no wait before bindery, and it does a couple things more. It reduces the need for powder on the press (I’ll get to the digital part in a minute). It also resists yellowing, which is common with varnished pieces that are stored for a while. Ghosting problems also tend to be eliminated and it complies with environmental laws.
Normally, aqueous is applied to the entire piece (flood) as opposed to spot coating. On the down side, aqueous often costs twice as much as varnish.
• UV Coating is by far the most common small shop application, and has the highest gloss and rub-resistance of all the options. It starts as a clear liquid that is cured (dried) instantly with an ultraviolet light. It comes in a wide range of sheens, although some find it too shiny for some uses.
UV also resists additional imprinting so postcards, for instance, are commonly either addressed before being coated or are coated on one side only so the address may be imprinted on the uncoated side. Similarly, it is common for business cards to be coated one side only so that consumers may write on the backs of them.
Most UV equipment we see would be operated off-line, which provides only a flood coating option. UV gives more protection and sheen than either varnish or aqueous and, since it is cured with light and not heat, no solvents are emitted. You can coat 80-pound text and heavier, although cover weights are preferred. UV can be used on smooth papers only.
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.