Digital BW, The Print

Paul,

Look at the figure on page 9 in this article on my website (the link is public).

http://www.aardenburg-imaging.com/cgi-bin/mrk/_4569ZGxkLzBeMjAwMDAwMDAwMTIzNDU2Nzg5LyoxMzM=

It shows a real world example of the Epson R1800 GLOP in retarding gas fade of the OBAs in an inkjet paper. There are also several side-by-side spray versus uncoated sample test now in progress in the AaI&A database. You can search/sort the coating/laminate column to find some coated samples, then check for corresponding AaI sample numbers that have the same beginning code sequence in order to find the uncoated comparison samples. Also, Batch J that just recently started test,  I believe has some second pass MIS Glop coated samples with some Piezography inks.  May not be on high level OBA media. Hover, some coating tests are already confirming improvements even to the pigmented ink light fastness.  

My general conclusion from all the research I've seen is that unless one laminates or uses very heavy "varnishes" the coating thicknesses are too thin to appreciably block UV. The primary benefit of these thin spray coatings like Premier Print Shield, although often attributed to UV blocking effects, is actually due to the coating's retardation of the oxidation. In other words, sealing the micropores is helping to impede the oxidation effects and those effects can be caused both by gas fading and by light induced photo oxidation reactions. That said, the sealing is far from complete.  Again, the polymer coatings are too thin to be a perfect oxygen barrier.  Considerable permeability remains, yet it is reduced somewhat and thus the testing reveals a lightfastness benefit to many post coatings.

I do have some concerns about the aqueous based acrylic polymer coatings. These formulas typically smell of ammonia to me so the acrylic emulsions aren't just comprised of water and polymer.  I've seen some serious compatibility issues with canvas inkjet materials coated with HVLP spray guns and roller coatings sent to me by conservators, printmakers, etc., who witnessed real failures of these coated inkjet canvases in the field. But it's not a universal problem, so I don't want to leave anyone with the impression the water based varnishes are categorically bad. They often work exceptionally well by imparting decorative properties as well as increased durability, but there's a wildcard in there somewhere.  Much more research is needed with these types of coatings and various inkjet media.

kind regards,
Mark
http://www.aardenburg-imaging.com




--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul" <roark.paul@...> wrote:
>
> "Mark" <mark@> wrote:
> 
> > I believe there are several factors that influence OBA burnout ...
> > 
> > 2)... When located in top microporous coatings, the OBAs are extremely sensitive to oxidation (just like other dyes)...
> 
> Mark, do you have any tests or information that indicates whether the use of MIS or other "glop" (glossy optimizer) seals the paper well enough to influence this oxidation rate?
> 
> With respect to the sprays there has been some speculation that part of the benefit comes from sealing the micro porous coatings, which presumably slows the oxidation rate.
> 
> Paul
> www.PaulRoark.com
>