Digital BW, The Print

Just a quick entry to update you on the results of a 6 week fade test using
a variety of alternative coatings on piezoBW prints.

Although I can't release the specific formulations that I am using I wanted
to share some general principles that should apply to the testing that
others on the list are doing.

I prepared 21-step wedge prints on Eclipse Velvet (350gm) and Orwell
(310gm).  These papers were chosen because they are much easier to coat than
lighter weight papers.  The prints were prepared using a 1160 with CIS.
Based on extensive pretesting (more than 50 different coatings combinations
on a dozen different papers) I selected several coating systems for testing.
All of these systems involve applying one to two coats of a seal coat
followed by from one to three coats of a top coat.  The seal coat is used to
thoroughly wet out the pigment and paper and seal it so that the top coat
sits on top and maximizes the gloss (dmax) increase.  All coatings were
applied with a good quality Oil painting varnish brush.  Coating
approximately 30 letter sized sheets of prints was done in an evening
(intermittent activity over 4 hours)...this included all coats.  Spirit
based prints take several days to dry while water based prints are dry the
next morning.  Fades were conducted in an unobstructed south facing bay
window in Southern California.

Here are the basic conclusions:

1. 6 week fading can be reduced by at least 50% by sealing and top coating
prints.

2. More is not better.  A single seal coat (on Eclipse) and two seal coats
(on Orwell) followed by a single top coat showed just as much improvement as
the seal coat followed by 3 top coats.

3.  Spirit top coats did not produce better fade results than water-based
top coats.

4. Although all of my systems contained at least one product with
UV-inhibitors, more layers of UV-inhibitors did not produce better fade
results.

5.  There were not differences in fade between Orwell and Eclipse prints in
both the uncoated and coated conditions.

6.  While most inkjet papers can be coated (as long as the final prints are
waterproof), heavier papers are much easier to coat than lighter papers.
Less absorbent papers like Eclipse are easier to coat than more absorbent
papers like Orwell.

7.  Some papers benefit more from coatings than others and the profile of
coated papers can differ from uncoated papers.  In general Eclipse prints
looked better coated while Orwell prints looked better uncoated.  This may
correlate with initial Dmax--however, this is a complex issue and is open to
investigation.

8.  Tack is an important issue.  While all faded prints were thoroughly dry
after six weeks in the sun, some prints that were stored in the dark in an
envelope were still tacky.  This is a critical formulation issue and there
were coatings that gave satisfactory results.  It may be a good idea to
briefly dry prints that are coated with a heat gun or at least leave them on
a drying rack for several days before they are stacked.

Hope that helps,

Robert


----------------------
Robert Morrison
rmorrison@...

310-397-2704

4131 Bledsoe Ave.
Los Angeles, CA 90066