Digital BW, The Print

Coating Inkjet Prints

An idea that was introduced on the Piezo list by Bob Tyson was to 
varnish Piezo prints (or any inkjet print). Varnishing or otherwise 
coating an inkjet print can address several issues.

One of the most common dissatisfaction with B&W inkjet prints is that 
the Dmax (maximum density or deepest black) is not as black as a 
traditional silver gelatin print. This is due in large part to the 
fact that the most suitable papers for pigment inks have a matte 
finish. Coating an inkjet print significantly increases the Dmax and 
the overall contrast of the image.

Secondly the surface of inkjet prints is frequently rather fragile 
and easily damaged. A coating over the ink offers a great deal of 
mechanical protection.

Fading issues can also benefit from coating. The dyes used in inkjet 
inks are susceptible to fading from exposure to UV light. Many of the 
coatings available contain UV absorbers or inhibitors. If the coating 
does not, it is possible to add these substances. Even the pigmented 
inkjet inks benefit from UV protection since virtually all of them 
contain some dye to increase Dmax. 

Back when Bob Tyson brought up the idea of varnishing Piezo prints 
his idea was to use "alternative coatings," that is using coatings 
such as furniture finishes that were not intended to be used as art 
varnishes. This inspired me to visit the local art store to check out 
the selection of non-alternative or coatings intended for use on 
works of art. At the time I promised to give some of these a try when 
I had the time.

In the meantime Robert Morrison took up the task of trying artists 
varnishes on Piezo prints. Robert ultimately decided that the work he 
had done was of commercial value and is currently working with 
company to market a coating system specifically for inkjet prints. 
His system is currently under going trials and will not be available 
be a couple of months.

In any case, I decided to conduct my own trials in coating inkjet, 
specifically Piezo inkjet prints. Rather than waiting to the end of 
the tests and publishing a report I and will post updates as I go 
along. I am going to simply give you the information in roughly the 
order things occurred.

Some general thoughts on the subject.

As Bob Tyson aptly put it, "This isn't rocket science." nor is it a 
new science. Photographers have been varnishing their photos from 
just about day one but tapered off when the silver gelatin on clay 
coated papers took over the market. Both the air-dried and the 
ferrotyped finishes were popular and varnishing photos largely died 
out except for a small number including Paul Strand. (Bob, you have 
much more art and photo history than I, so if I err in this area or 
you have additional info please jump in.)

A lot of these varnished photos are still around and in good shape so 
I don't believe that archival issues should be too concerning. (I 
have some 30-year-old photos that were sprayed with Krylon that are 
still fine.) Given the advances in polymer technology, the materials 
available today should be superior to what was used on photographs 
100 years ago.

The traditional art varnishes are made from plant resins dissolved in 
solvents and oils. The most common ones are mastic, copal, and dammar 
for oil painting and, acrylic for acrylic paintings (although some 
artists use acrylic to varnish their oils).

I decided to not try the mastic, copal and dammar varnishes, as they 
are known to either start out yellow or turn yellow within 50 years. 
Dammar seems to be considered the best of the three starting clear 
but yellowing eventually. If you are wondering why oil painters 
knowingly use yellowing varnishes on their paintings the answer is 
that the varnish can be removed and a fresh coat applied. This isn't 
an option for Piezo prints.

I also decided to limit myself to brush application at this time. The 
canned sprays I have tried did not seem to have any effect on the 
appearance of the surface or the Dmax. I think they simply apply a 
coating that is too thin and dries to quickly to smooth out. Although 
they do provide some mechanical and UV protection.

First attempts:

Based on the posts to the Piezo list that Robert Morrison made I had 
gotten the two Golden acrylic varnishes he mentioned, the water 
soluble and the MSA solvent based both in gloss. I also got the 
DaVinci #50 varnish brushes he mentioned.

I found the water soluble Golden and the brushes at Dick Blick Art 
Materials (http://www.dickblick.com/)

The Golden solvent based varnish I bought locally at University Art 
Supplies. I did note that Rex Art (http://www.rexart.com) does carry 
the Golden solvent based.

Another excellent source for art supplies on line appears to be 
In2art. (http://www.in2art.com/index.shtml )

I also obtained a third coating based on a post by Marty Connelly(?) 
on the Piezo list who had mentioned using an aerosol product 
ClearJet . I checked out the web site and found that they sell this 
in quarts and gallons and also make a water based version called 
ClearSheild. These are vinyl coatings that are sold to sign makers as 
a coating for inkjet printed signs and banners used in outdoor 
displays. I chose the water based ClearSheild in gloss.

(NOTE: If you order some of these items over the Internet or by phone 
you will run into some shipping limitations. Hazardous materials are 
either not accepted for air shipment or only at a higher charge. Even 
ground shipments sometimes involve a "handling fee." This is not just 
the solvent-based products. An 8 oz. bottle of Golden water based 
varnish was considered hazardous.)

I made identical prints on Lumijet Classic Velour (aka Hahnemuhle 
German Etching, Lyson Standard Fine Art, ConeTech Orwell), ConeTech 
Wells River (aka Hahnemulhe William Turner 190 gsm), Kodak Ultima 
Satin and ConeTech Matte (aka Hahnemulhe Photo Matte). All on 8.5 X 
11 paper.

I needed something to tape the prints to so I took three empty 
cardboard boxes. Opened the top and bottom and cut one corner. I 
taped four sheets to the inside surface of the flattened box and laid 
it out on my deck (which would greatly benefit from some spilled 
varnish). My working quarters are rather small and while I could coat 
a print or two inside a large number would be impossible.

Trial #1

I started with the ClearSheild Gloss. The directions said to use it 
undiluted straight from the can. I applied two coats to a print on 
Wells River and 1, 2 and 3 coats to three prints on Lumijet Classic 
Velour. I let the prints dry about 1 hour between coats. While the 
prints were drying I picked up the flattened cardboard box and stood 
it on edge in its original box shape to help protect the coated 
prints from dust.

First mistake. Undiluted may be fine on the vinyl substrate the 
manufacturer had in mind but on paper not a good idea. The absorbent 
paper soaked up the thick, undiluted coating unevenly. This resulted 
in some slight mottling in smooth toned areas of the prints. This 
also resulted in an uneven gloss on the first coat.

Second mistake. While being careful about runs or puddles on the 
print area I didn't check the edges of the print or the backing 
cardboard so when I stood the cardboard on edge I got a few runs down 
a couple of the prints and some behind a print gluing it to the 
cardboard.

Impressions/Conclusions:

Wow! When you put that coating on and it is wet, it is like looking 
at a silver print in a tray of water! Dry down to reality. The 
ClearSheild Gloss gives a new definition to the word gloss. Man this 
stuff shines like an RC glossy. Like a lamination only brighter. 
Howeve, the total result is not smooth like a RC print. The paper has 
texture, there are signs of residual brush strokes and small bumps 
from tiny air bubbles that did not fully release from the coating 
before it dried.

On the 1 and 2 coat prints there is some variation in the gloss. It 
appears that if you do not get a nice smooth, even coat on the very 
first coat, the imperfections carry through into the next coat or two.

Dmax is greatly improved as expected. I think that ClearSheild Gloss 
is way too glossy for my tastes. With the super high gloss, light 
reflects from the many small surface bumps. It is hard to find a 
viewing angle that doesn't show some sparkle points. The Wells River, 
being a smoother paper was much better in this regard.

I did not observe any buckling in either the Wells River or the 
Lumijet Classic Velour. Both took on more curl but look like they 
would flatten out under a standard window mat. They are much flatter 
than an air-dried silver gelatin print. However, now that they are 
coated I doubt they could be dry mounted. Wet mounting should be 
feasible if required or desired.

Antonis Rico who saw Robert Morrison's efforts pointed out, these do 
not look like sliver prints. The finish looks very similar to the 
surface of a varnished oil painting on canvas, which shows the 
variation in paint thickness, brush strokes and the underlying canvas 
texture. This is not going to be to everyone's taste. I showed my 
wife a coated and uncoated print and her reaction was that she liked 
them both. I sort of shared that feeling but as a former silver 
printer that extra Dmax is attractive.

Trial #2

For this I used the Golden water-soluble acrylic varnish. Once again 
I used 1 print on Wells River (3 coats) and 3 prints on Lumijet 
Classic Velour (with 3, 4 and 5 coats). I diluted the varnish with 
water as directed on the bottle adding approximately 1 part water to 
2 parts varnish (Note: In the varnish world this is considered a 50% 
dilution). This was more than the 20 to 40% recommended but I assumed 
the recommendation was for a painted surface.

First Mistake: Similar to trial #1. The coating was still too thick 
and did not spread out nicely on the first coat. Coverage was better 
than with the undiluted ClearSheild but the first coat dried with an 
uneven gloss indicating uneven application. Second Mistake: Same as 
in trial #1. I did them at the same time and had not yet noticed the 
run problem. Impressions/Conclusions: The Golden is not as glossy as 
the ClearSheild and leveled better giving a nicer finish at 3 and 4 
coats. At 5 coats the gloss is starting to get close to the 
ClearSheild gloss level. Once again the Wells River with its smoother 
surface had fewer spectacular reflections. Small bumps from tiny 
unreleased air bubbles was a problem with the Golden too but not as 
bad as the ClearSheild. Again great Dmax improvement.

Trial #3

Just as an experiment I tried brushing an undiluted coat of 
ClearSheild on a print on Kodak Ultima Satin. As expected the print 
smeared but very slightly. I was surprised how little. Here the brush 
marks are very obvious. Looking past these flaws the thick coating 
really put the paper solidly into silver gelatin territory in my 
opinion. Although RC rather than fiber. If you like this paper, I 
would recommend pursuing this with a satin finish coating and an 
airbrush application perhaps. 

Trial #4 This was with the ClearSheild using a 1 to 2 dilution on a 
print on Wells River and one on ConeTech Matte. The first coat went 
more smoothly than trial #1 and the final result on the Wells River 
was better but still too glossy. The ConeTech Matte is too light and 
buckled up badly. Also the brush marks are more noticeable on the 
smoother surface. It would need to be mounted before coating.

Trial #5

This was with the solvent based Golden acrylic varnish MSA. There 
were literally no instructions on the can at all. Checking their 
website I found a wealth of information on their products and on 
varnishing in general. A must read if you are interested in this.

http://www.goldenpaints.com/ http://www.goldenpaints.com/varns.htm

One of the first things I found was that the odorless paint thinner I 
had been sold to dilute this varnish was not appropriate. In fact 
they only recommend thinner is extra distilled or refined turpentine 
to prevent let down shock (thickening or lumping). Unfortunately that 
is not readily available. I made one attempt to put a single 
undiluted coat on a print on Lumijet Classic Velour without much 
success.

After going through the material on Golden's website I reached some 
conclusions. The Golden MSA solvent varnish is probably really great. 
For starters, all the HALS and UV absorbers that Jon Cone has 
mentioned on the Piezo site already in the varnish. In general, 
solvent varnishes will level better and have fewer problems with 
foaming and bubble release. In addition solvent system polymers are 
generally stronger and more durable. The Golden MSA probably offers 
really great protection.

I also concluded that this really isn't a workable system for me and 
probably not for many other users. You need to have a very large 
working space and be willing to devote the time required. Golden 
recommends 4 brush coats or 8 spray coats for best protection. Since 
4 to 6 hours of drying time is required between coats and a final 
curing time of several days after the last coat before stacking, the 
process will really stretch out. Also, this is a solvent based 
coating that needs to be done and allowed to dry in a space separate 
from where you work or live and in a manner that does not present a 
fire or health hazard. In addition commercial use in may urban area 
will require air pollution permits and/or abatement.

I intend to pursue this on at least a couple of prints so that I have 
the comparison point. I am in sunny California and I can leave them 
outside over night. Other than that I will be pursuing only the water 
based materials that dry more quickly and will allow me to work 
inside once the rainy season arrives.

Some overall conclusions at this point:

It should be pointed out that the Piezo prints I coated were printed 
with using a water insoluble pigment ink set. If you want to coat or 
varnish a print that was made using a water soluble dye based ink set 
you will need to apply a spray coating such as Krylon to fix the inks 
in place and protect them from the water in these coatings.

While I need to work on my brush technique for that critical first 
coat, I suspect that brushed on coatings will always be somewhat 
uneven. This may be good or bad depending upon your artistic taste. 
We are used to seeing photographs that have very uniform surfaces. 
The brushed on coatings so far add a bit of a hands-on look. I think 
that some unevenness is probably okay and would be down played under 
glass.

Which reminds me that someone suggested that the coated prints could 
be framed and displayed without glass. I don't think that this would 
be a good idea as some of the coatings are not all that tough and 
your matting would not last.

One item I gleaned from the Golden information is that their 
varnishes are designed to be removable. In the painting conservation 
world the ability to remove an old coat of varnish along with 
accumulated dirt is essential. To make the varnishes removable they 
have essentially not designed them for maximum toughness. Something 
to keep in mind.

Another piece of information was that polyurethanes are the toughest 
polymers available but were not considered for painting varnishes 
because they do not pass the test of being removable. Also the more 
common aromatic polyurethanes yellow but the aliphatic ones do not.

Since there is no possibility of removing at least the first coat of 
varnish from a Piezo print as it sinks into the paper I will try a 
polyurethane in my next set of trials. I picked up a can of Varathane 
Diamond Wood Finish Exterior Semi gloss at Home Depot. I contacted 
Varathane and they confirmed that it was an aliphatic polyurethane 
and would not yellow. I chose the Exterior as it is advertised as 
having UV blockers and being more flexible during extreme temperature 
changes.

I am also thinking of a better way to get the first coat on the paper 
to even out the final result. The possibilities are silkscreen, 
airbrush or draw down rod. I have a bit of experience with silkscreen 
and it offers the chance to make a heavy first coat. Airbrush I have 
no experience with and might be hard to use at the dinning room 
table. Draw down rods I only know as something used to spread 
chemicals during platinum printing, something I have not tried.

So at this point the next set of trials will be the vinyl ClearSheild 
in semi-gloss, the acrylic Golden water based (maybe in semi-gloss) 
and the polyurethane Varathane in semi gloss. Currently waiting for a 
paper shipment and some free time.

All comments and suggestions welcome.

Martin Wesley