Digital BW, The Print

Robert,

Thank you for the fade test results. I will throw some comments and 
questions into your message below.

--- In DigitalBlackandWhiteThePrint@y..., Robert Morrison 
<rmorrison@p...> wrote:
> 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.

A mechanical question for you. Did you use a drying rack for the 
prints after you coated them? Finding a space to spread out 30 sheets 
would be an obstacle for most. How did you hold the paper down while 
you coated it or did you just manually hold it in place? Did you coat 
the entire sheet edge to edge or just the image area?

I have found it desirable to leave the prints flat for a while after 
each coat to eliminate the chance of runs or sags in the event I 
missed any excess build up.

> 
> Here are the basic conclusions:
> 
> 1. 6 week fading can be reduced by at least 50% by sealing and top 
coating
> prints.

Did the prints fade evenly across the tonal range? Or did the high 
lights fade more quickly than mid-tones?

Did you observe any color shift in the inks or the paper base? Since 
the Eclipse Velvet and Orwell both appear to have brighteners (the 
Eclipse appears to have quite a bit) did you note any yellowing of 
the base? Was there any degradation in the brighteners' ability to 
fluoresce? Did it vary between the coated and uncoated prints?

What about yellowing of the coatings? I know that there is some 
initial yellowing of the prints by the coatings, some coatings more 
than others, did this stay constant during the fade test?

> 
> 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.

That is very interesting and good news at the same time. Some of the 
combinations I tried did not benefit in appearance from multiple 
coats.
> 
> 3.  Spirit top coats did not produce better fade results than water-
based
> top coats.

Also good news as the solvent based varnishes are much more difficult 
and unpleasant to work with.

> 
> 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.

Did your coatings cover a range of different UV-inhibitors? Did some 
inhibitors out perform others?

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

Can you quantify how much fade you did see?

> 
> 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.

Heavier and a medium smooth texture. I found Museo to be the champ 
for taking a nice coating and not overly revealing brush strokes. I 
managed to coat some EAM but it was difficult. Have you tried coating 
any dry mounted prints?

> 
> 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.

My attempts to print with Piezo on the Eclipse Satine and Velvet were 
very poor with extremely weak and veiled blacks. Coating some of 
these same prints utterly changed them from unacceptable to very 
good. The MIS inks seem to be much better suited to these papers.
> 
> 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.

Oops. There's the answer to my drying rack questions. Any 
recommendations as to make, model and source? I would guess that the 
tacky prints were the Golden acrylics. The polyurethane and vinyl 
coatings I tried did not seem to have this problem. I did notice that 
all of the coated prints seem to be retaining the odor of the coating 
for a very long time.

I am concerned that Golden's approach of making an easily removed 
painting varnish is not applicable to coating paper prints, and may 
have properties that are undesirable for this application. Since it 
seems unlikely that the varnish could safely be removed from a paper 
print, taking a more permanent approach would suggest that the 
aliphatic polyurethanes would offer much greater strength and 
mechanical protection over the acrylics. I also found the Varathane 
Diamond product much easier and cheaper to work with.

Thanks,

Martin Wesley