Digital BW, The Print

John,

>It looks like PremierArt Printshield is being proposed as a
>spray for papers like Epson Semi-Gloss to eliminate bronzing.
>Sounds good.  You get a glossy print with good dmax and no
>bronzing and a protective surface.

Yes, add to this a Wilhelm dark storage life of over 200 years, and it makes
an interesting package.

>But with EEM and the like, the Mayer rod with polyurethane seems
>to give the same results.  And even though it's a little more
>involved than the spray can, EEM is WAY cheaper than glossy papers.

EEM is acidic, having a dark storage life of 110 years, according to Wilhelm
-- and that is under ideal conditions.  When acidic materials have been
encapsulated, they have in some tests deteriorated 10 times as fast.  If the
acidic H+ ions are cannot escape, they will have nothing to do but attack
the un-buffered EEM paper.  So, to get an equivalent life, you'd have to go
with a buffered cotton paper.  The price comparison is then not as good.

>So why use the RC paper with Printsheild approach?

There are a number of reasons.  

One is the existence of the Wilhelm tests of the PremierArt spray.  I don't
have one for the polyurethane coating I was doing.  

I was not able to scale up the Mayer rod.  Some claim to have been
successful with 16x20, but I never saw one.  I would have gone to a thicker
glass and continued to try if I had not been intrigued by the barrier
papers.  So, one reason is that I think I'll be able to scale this process
up to any size.

I think the carbon pigment may be best protected if it is entirely
encapsulated.  In my high humidity fade tests, the polyurethane coated test
strip did worse than one that was not coated.  I think the reason is that
humidity was getting into the print from the back and then was not dried out
the way the non-coated test strip was.

I am most impressed with the solvent based coatings in terms of their
ability to surround the particles and protect them.  The solvent based
materials are in liquid form when they hit the pigments.  The liquid
surrounds the particle and then hardens.  The water borne materials just lay
on top.  It appears to be the difference between water-based paint and
oil-based.  The later soak in and stick better.  The solvent based sprays
are going to do a better job of encapsulating the pigment particles,
protecting them from the environment, and sticking them to the paper.  A
tech person with one of the acrylic companies also said that the
solvent-based UV protective sprays are much more effective at UV protection
than the water-borne materials.

With the 4000, we'll be able to go with either paper easily.  I'm not
abandoning the matte papers, but it is time to optimize the B&W systems for
both now.

The barrier (RC) papers may be the easiest, least capital-intensive way to
get very durable, high dynamic range display prints.  At least it is worth
exploring.

Paul
www.PaulRoark.com