Hello Mark,
Just wondering if you have ever tested the Premier Eco Print Shield Aqueous Based coatings. They of course come in Matte, Satin and Gloss varieties, but must be applied by brush, roller or HVLP sprayer.
Gary
Hi Gary, yes I should have mentioned the Eco Print Shield to be more clear in the discussion that Premier Print Shield is an entirely different beast altogether from the aqueous-based coatings designed primarily to be rolled or applied by HPLP spray guns onto inkjet canvas media. Eco Print Shield is indeed in this class of water-based acrylic emulsions and thus chemically similar to other popular aqueous-based acrylic coatings like Breathing Color Glamour II or ClearShield Type C LL coatings. These aqueous-based coatings are considered to be more environmentally friendly, and even with typical dilutions they generally create a much thicker coating than Premier Print Shield or its low viscosity solvent-based counterparts like Moab Desert Varnish and Hahnemuhle Protective Spray. So, on the upside, the aqueous based acrylic emulsion type coatings will make a thicker, more physically robust top coating that should protect the canvas image from handling abuse and airborne grease and grime much better than the thin coatings achieved with Premier Print Shield, etc.
Unfortunately, the testing I've done on some of these aqueous-based coated media suggests once again that there is no free lunch. I haven't done a lot of samples since I got little call over the years to test canvas media, but in the samples i did receive, I typically asked for and received a control sample printed with same printer/ink/media batch but left uncoated, and I then ran the coated samples side-by-side in test along with the uncoated control sample so that we could directly ascertain the influence of the coating on the lightfastness of the product. There are a few examples of these paired-comparison type tests for aqueous-based coatings in the AaI&A database. For example, Glamour II was tested as was the Clearshield Type C, but I don't have any tests for Premier EcoShield. ID#'s 298 and 299, as a specific example, are the head-to-head comparison of Breathing Color Chromata White Canvas printed on an Epson 9800 printer with Epson UCK3 OEM ink set, where ID#298 was HVLP spray located with Glamour II whereas ID #299 had no additional coating. The coated sample got an AaI&A rating of 36-67 Megalux hours while the uncoated sample did much better with a rating of 106-119 megalux hours. This was a surprising finding that I didn't expect, and it played out the same way in other similar tests.
While the solvent based Print Shield in essentially all cases I've tested does admirably improve the light fastness of the print while also improving or leaving unchanged the initial image quality when pigmented inks were used, the obvious trend for the aqueous-based coatings is that light fastness is actually reduced despite manufacturers' claims to the contrary, sometimes by a small amount but sometimes by quite a significant amount as in ID#298 versus ID#299 cited above. Again, I should caution that I don't have a huge population of tests to draw sweeping conclusions from, but a concerning trend is that aqueous-base coatings apparently have some chemical compatibility problems with pigmented inkjet inks (at least Epson Ultrachrome sets to be specific). What may be happening is that the alkaline chemistry (typically ammonia) needed to emulsify and disperse the acrylic polymers into a primarily water-based solution is in all likelihood also attacking the pigmented ink resin encapsulation polymers in an adverse way when the coating gets applied to the canvas surface. Once might be able to avoid the issue by laying down a pre-coat layer of a solvent spray like Print Shield, but that would be much more work and probably unsatisfactory on many levels to folks who make canvas inkjet prints
And this pre-coat suggestion would have to be tested to see if it in fact is able to adequately isolate the resin encapsulated pigments from the aqueous acrylic top coat during the application and dry-down period.
All this said, I realize that many canvas prints are intended for commercial and home decor markets where the need for long term light fastness is not so great and where only medium term print permanence (5-25 years on display) is probably all that is necessary given that people often redecorate before most prints are likely to fade. In this market, the ability to clean the print surface and avoid mechanically induced damage is probably the far greater concern for overall product integrity.
cheers,
Mark
http://www.aardenburg-imaging.com
