Paul's Coating Procedure and Materials
2002-11-15 by Paul Roark
I've had several questions about what I'm doing with respect to coating
prints. So, below, is a brief description of my procedures and materials.
This is still experimental, and most of the credit must go to Robert
Morrison, who will have his own special-made coating material out soon.
Anyway, here is what I am doing as of today:
I have been experimenting with coatings to raise the dMax to over 2.0,
making the inkjet prints at least comparable to my silver prints. Also, I'm
interested in making the prints more durable. Frankly, my goal is to
produce a print that is so tough that it can be displayed without glazing.
Once the glass is gone, the dynamic range of the print can really shine. I
don't expect conservative gallery types to accept the idea very quickly, but
side-by-side with glazed B&W prints, the unglazed, coated inkjet prints look
really good.
Sprays cannot give the dMax increase that I am looking for. A thicker
coating is needed.
So far, I favor applying the coating with a #15 wire-wound ("Mayer") rod
(from Diversified Enterprises 800-833-4644). For 8x10" prints I've been
using a 16" (12" of winding) 1/2 inch thick rod that sells for $22 (but
there is a $25 minimum). It's the only process I've tried that can do a
perfect finish in one coat.
For coating material, some like the water-based acrylics for the first coat.
Golden and Liquitex both make good acrylics. The readily-available Liquitex
version at 3 parts Liquitex to 1 part water works well. Among the acrylics,
I favor something like the Liquitex because it has no UV inhibitors, which
can yellow the print too much.
I currently think polyurethane ("PUR") may be a better coating. It's
superior toughness and resistance to humidity and chemicals may have
advantages over the acrylics. The best practical answer I've found is the
water-based (easy, even if not at tough as the 2-solution,
industrial-strength, solvent-based ones), aliphatic (non-yellowing),
Hydrocote (800-229-4937) Polyshield Gloss. This is available in quart size
via mail order. The #15 rod applies it easily with no dilution. It dries
very quickly, but takes about 7 days to totally cure.
Eclipse Satine paper is the best one I've found for coating. It stays nice
and bright with a coating, and looks great with only a single application.
The finish ends up a pearl/luster that is very nice, although this is
subjective. For a flatter finish, Legion Photo Matte may be a good choice.
It also coats well with a single application.
EAM and PhotoRag take two coats with the #15 rod. I've ordered a couple of
other sizes and will experiment with them to see if I can find a one-coat
workflow that works with these papers.
To apply the coating with a rod, I tape the top 1/8 inch of the print to a
piece of glass using Scotch Removable tape. (The glass is for a smooth, flat
surface that I can razor off dried coating if necessary.) For some papers it
helps also to tape down the bottom corners. I've been using a couple sheets
of copy paper under the print.
About 7 cc (for an 8x10) of Polyshield pulled straight from the can with a
syringe fitted with an MIS bottom-fill attachment is used to lay a "bead" on
the tape and glass above the print. I pull some water into the syringe and
discharge it immediately a couple of times to stop the PUR from setting up
in the nozzle.
Just before pulling the rod across the print, I use a blower to be sure
there is no dust on it. Since the can of PUR is only open long enough to
pull out what I need, there should not be any significant amount of dust in
the coating material (I hope -- so far, so good).
After the "bead" (or small, long pool) of coating is on the tape and glass
above the print, I pull the rod through the bead and down across the print.
The weight of the rod supplies most of the downward force needed. I don't
roll the rod, but rather drag it smoothly and not too slowly, keeping the
speed of the pull as constant as possible. After I've pulled the excess
coating away from the bottom of the print, I immediately rinse off the rod.
I definitely don't want the PUR to set-up on the rod.
I quickly remove the tape from the print. If the PUR starts to set-up
before the tape is pulled off, it will pull off part of the print paper with
it.
I usually put the 8x10 print on a dry paper towel as soon as possible. The
screw-driver that I used to open the can makes a handy tool to run under the
print edges to separate them from the paper and glass under the print.
A damp sponge soaks up the excess coating material and will clean the glass
easily after you're done.
Once the glass is clean and dry, I usually pull the print on its paper towel
back onto the glass and dry it a bit with a hair drier. By this time it is
also dry enough to just hang up to dry.
Between the tape, handling and other problems, I lose a little less than 1/4
inch of each print edge, but that still leaves a good 8x10 print area. When
cutting the coated prints, I find a hand-held, rotary cutter on a cutting
mat does a superior job.
I'm still experimenting with this, so my materials and methods may change.
Paul
http://www.PaulRoark.com