Canvas coating pinholes and surfactants...

[philbaum]

There's the occasional report on this forum about canvas coating pinholes, and when i started experiencing the problem, i searched on here and read the threads.  Coating pinholes, in my case, look like someone sprinkled white salt over you picture.  Over black, they look like small whitish points about 1/8 to 1/4 inch apart with little craters in the coating above these points.  If you look at the coated picture with pinholes, at a side angle with a light glaring at it, it looks rough and pitted - nothing i would want to buy in any case.

coating pinholes is not my term, but what you will find the most results with if you search lula for it.

So my story is this:  For 16 months I've been printing my pictures on Premier Art satin canvas with photo black and selling them - over 80 of them in the last year.  Then i bought an Epson 3880 and switched to matte canvas and matte black ink.  Immediately i ran into what i call "pinhole hell".  No i'm a small volume printer so use a roller, Delft water based polyurethane, and that worked fine till the pinholes developed.  I started checking room temps and they were fine.  I thought perhaps the unapplied polyurethane can had frozen and been damaged so bought new cans, but had the same problems.  In checking the responses to old threads on here, the recommendations were either to do thinning with water, switch to Glamour II if rolling, or use a sprayer.

About this time, i checked with my brother who was using the same coating, the same Kodak satin canvas and not having the problem at all.  In later questioning, it turns out he was using photo black with his canvas vice the matte black i was using.  

I finally decided to order a new coating, ArchiveCoat from this company:  https://www.canvasandpaperwarehouse.com/ProductDetails.asp?ProductCode=PermaliteSatin#.UwZBsPldWSq

In discussing my problem with "James" on the phone, he said that my problem called for additional "surfactant" and i could do this by adding 3 drops/gallon of ordinary kitchen detergent to the varnish i was using.  This was just a comment and not an official recommendation but it was extremely helpful to me in figuring out what happend to my printing results.  He told me that using photo black vice matte black could be the difference between no pinholes and pinhole hell that i've been experiencing lately.  So i'm going to do a test today and add a coupla drops of detergent to a quart can of my old varnish and see what happens to a test strip of canvas.

Even without the testing, I'm leaning towards his explanation because it never seemed to me that the coating i was using was covering the picture that well with the matte canvas and matte black.

By the way, this is a definition of surfactant i found on the internet:
Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants

 If i had known about this earlier, it would have helped me get through this problem.  IMO

[bill t.]

Looking forward to your report!

I have wondered if a few drops of Kodak Photoflo would be useful addition for those water based varnishes where there is a tendency to puddle on smooth media.  A kind of cheap leveling agent.  Was the slipperishly sensational surfactant for negatives.  Would want to keep a close eye out for subtle ink pickup on the roller.

[huguito]

Hi Phil

Can you remember what was your choice of Deft varnish or laquer that you where using? 
Is it very clear or does it create a strong color cast?
I am looking for something very glossy to finish up a large canvas piece

Hugo

[bill t.]

Timeless Gloss is very glossy indeed!  Practice makes perfect, try some junk canvas first.  One rolled coat or two sprayed coats and your close to maxing out the available glossiness.

MinWax Polycrylic Gloss is also extremely high gloss, transparent, and neutral colored.  But it dries brittle which may or may not preclude stretching.  Best to use Polycrylic for mounted canvases only.  Handles much better if you dilute with about 10% water, and can be sprayed at that dilution even though the literature says not.  Wear a mask with an organic filter, it's nasty stuff in the air.  Timeless is actually cheaper and has better storage qualities.  But you can buy Polycrylic down at the megastore.

Those mounted glossy canvases are pretty impressive if you can get the surface right.  Can compete in color and contrast with facemount and other wiz-bang processes, while looking a whole lot classier.  But never stretch a glossy canvas, looks like cheap crud because of multi angled reflections.

[philbaum]

Hugo,
Deft "Water Based Polyurethane, Clear Gloss. "all weather UV protection" - so its the exterior version.  We have tried the interior version, but the exterior version is a few dollars more and seems to have better adherence.  We do get a small amount of finish cracking on the folded canvas on the corners.  I'm not getting cracking on the bar edges if the edges are properly radius-ed.  We get clear finishes with this product.  I had at one time tried another polyurethane, solvent based, and it left a yellowish cast on the canvas. 

The company that i referenced is selling their 'ArchivalCoat" which James, store rep, says he uses and it works very well.  price is $68/gallon which, with shipping, is about the same price as the polurethane that i had been using.  It arrives on Monday, so i'll see how that works.

[huguito]

Hi Bill
Thanks for the info
I like timeless but is a bit expensive, I don't sell my prints so I try to pinch a penny when I can
I will pick some Minwax and try it

Hugo

[huguito]

Using any of the polyurethane varnishes sugested, In the case of mounting a canvas to a board, like gator foam.

Would you glue the canvas to the board and then apply the varnish?

I am thinking if the water in the varnish could weaken the adhesive between the canvas and the board?

Would be better to coat the canvas and then mount to the board after is finished and let to rest for a day or so fully cured?

One or two heavy coats or several thin coats?

Thanks

Hugo

[bill t.]

Coat first.  For Polycrylic mount the print within a day or two of coating while it is still flexible.  Minimum times between coating and mounting are about 4 hours for either Timeless or Polycrylic.

For both Timeless or Polycrylic I get the best results with about 10 to 20% dilution with water, depending on ambient humidity and temperature.  The hotter and drier it is, the more I dilute.  I feel the dilution allows the varnish to lay on surface completely wet for enough time to level and smooth out nicely, whereas with the undiluted paints the solution can land on the surface in a slightly tacky state which reduces gloss and evenness by quite a bit.  For any given condition Timeless needs more dilution than Polycrylic to avoid a "dusty" surface feel.

Polycrylic produces a much smoother, more leveled coating that basically preserves the texture of the media, whereas Timeless tends to exaggerate the texture a bit. So Glossy Timeless is a little more satin-like than Polycrylic on the same textured media.  For either spraying or rolling you need about 15 to 20 grams total application per square foot for a well-leveled, glossy finish.  You can get that with one rolled-on coat, or about 2 sprayed-on coats.  Trying to apply single, sprayed-on single coats heavier than about 10 grams per square foot usually results in runs, especially off of masking tape or clamps or whatever you use to hold up the print.  I usually spray 44" x 90" sheets of media taped up on a vertical backing.  Two coats that empty the gun by about 240 grams each is about right.  I almost always weigh the gun before and after each pass as a quality control measure, which keeps things consistent over the long term.

In some states you can only buy Polycrylic in quart cans at about $23 each.  Locally I can buy gallons at $48.  So depending on where you live Timeless may or may not be a better deal.  Partially full cans of Polycrylic tend to form skins and suspended globs much faster than Timeless.  So unless you coat at least every other day Timeless will give you better shelf life for opened cans.  Lots of other ins and outs with those varnishes, but those are the main ones.  With water based varnishes you need to clean the gun after every use, much more so than with solvent varnishes.  You also need to filter the paint as it goes into the spray cup, and if possible use a stem filter for underslung cups.

And FWIW Polycrylic has no anti-UV qualitites, and in fact may contain a tiny amount of OBA's.

[philbaum]

Well i did a little test.  I had a matte black image occupying about 1/2 the area of a 13x19 sheet of matte photo paper.  poured out a small amount of varnish from one of the suspect quarts, added one drop of liquid soap (these are large drops :-)) to the small pool of varnish and mixed it in good.  This is probably equivalent to 8 drops of soap per quart, way above the 3 drops/gal recommended by my store rep. James.

Took a brush and spread the varnish, It spread like melted butter - way smooth.  No sign of pinholes at all.  Now need to repeat the test on a sample of canvas.

[jferrari]

Well i poured out a small amount of varnish from one of the suspect quarts, added one drop of liquid soap (these are large drops :-))

<Sarcastic> --- Hope you're using the special name brand, archival-quality, acid free, liquid kitchen detergent soap product substance. Seriously, what will your response be when your customer says "Say, this print smells different than your competitors, so lemony fresh!" I think you might want to use Timeless, Glamour II or another product specifically designed for our industry.

[philbaum]

I think you might want to calm down a little bit.  I'm not doing this to sell my test prints to customers, but to find out a little bit more information about why some products work and other products don't.  IF you're not interested, why are you spending your time reading this?

When i mentioned my observations to a factor rep for the link i provided, he knew exactly what i was talking about.  But i've read several threads in printing forums where people had seen the phenomena, but spent endless posts speculating what to do about it.  What a waste of time when the answer is out there.

[huguito]

I think that not every image, in every case, needs to be printed to last 500 years in immaculate condition.
I am trying to see, at this point, how certain images I have, look on different substrates and finishes.
That's the main reason to find up the cheapest ways to get the look I am imagining without spending crazy money buying archival supplies that may end up unused if the final look is not what I want.
Keep in mind that this is just a hobby/obsession for me, I don't sell my prints, so money spent doesn't come back to my pocket after selling.
And thanks very much to everyone of you for sharing your experiences and knowledge, it is incredible helpful

Hugo

[huguito]

Reporting on a test of the results after applying all the info from this post

I cover a print I made in Canon Matte canvas, its an image with highligts, big very dark areas, and some strong colors.

Got a quart of polycrilic in home depot, add 10% of distilled water and just a tiny touch of dish soap, a little itty bitty fraction of a drop.

I am not sure if this thing its archival, or if it will yellow or crack overtime.

But is very even coverage, no marks, no pins or holes, and a very beautiful shine, looks a lot like prints I made in the canvas that breathing color calls silverada

I will mount it and then leave it under direct sunlight for a couple of days to see how it turns out

Thanks very much

Hugo

[bill t.]

One test is worth 100 posts.  Isn't it amazing what high gloss does for canvas.  Done as well as it can be done, it can outshine facemount glossies on the same wall while looking sooo much less plastique!

[philbaum]

Been way too busy to do much more on this subject.  Joined a gallery, put up a club show for March, been on call for playhouse pics, etc.

But i did do two prints and one test today.  The test was using this product called "ArchivalCoat" from Permalite.com.  Made specifically for coating inkjet photographs.  Tried it on a 11" long test print on matte canvas with matte black ink.  Applied it at the exact temperature of 72 deg specified by the manufacturer, they didn't require thinning so i did't do that.  Says its good for spraying or rolling.  I didn't want to go to the trouble of cleaning out a roller for such a small amount so used a foam brush. 

Results were that i had significant pin holes and also brush strokes.  I think the brush strokes would be gone if i had used a roller, but consider the pin holes would still be there.

Then just now, used a quart of polyurethane satin to coat a 3 foot long print done on satin canvas and with photoblack.  This was done with a quart that i previously had marked BAD because it had produced pinholes on matte canvas with matte black.  Well with photoblack and satin canvas - NO PINHOLES.  This is the second print i have made without pinholes, but using 2 different quarts of polyurethane previously marked as bad because they produce pinholes in matte conditions.  No liquid soap was used on these last tests.

Clearly the finishes i used, both polyurethane and the ArchivalCoat (product made specifically for inkjet photographs) produced pinholes due to either matte black and/or matte canvas.  The interesting test, which i'll do next is to see if pinholes are produced when photoblack is used on matte canvas.  I think when coatings are used with spray equipment, as numerous posters report, there is no problem with pinholes - i think.  I have a compressor but i hate to get into the spraying for the amount of work i do. 

[bill t.]

Every coating I have rolled or sprayed has worked much better when diluted somewhat with water.  Much better application, much better leveling, much subtler dried surface qualities.  Usually the difference between "straight" and diluted 10% to 15% with water is night and day as far as appearance goes.

I can only guess that the undiluted concentrations may give better results when stretching, perhaps a thicker coat has less tendency to crack.  So any testing of dilution should include an evaluation of how stretching characteristics might have been compromised.  Since I always mount canvas I can give no feedback on that, except that dilution in no way seems to compromise canvas mounted to Gator.

[philbaum]

Thanks Bill, I was wondering about thinning myself.  Another thing to test.  I don't particularly care what works, just so I know what the boundaries are to produce a consistent result. 

[bill t.]

The boundaries are probably pretty wide.

I don't experiment much with spraying, as I like the look I have now.  But I often roll coatings onto test strips and there I try lotsa stuff.  Dilutions of say Timeless and Polycrylic down to about 50% produce interesting results.  Gloss in particular starts to become more matte-like at high dilution, but with less hazing of dark areas than with "normal" matte coating concentrations.  Thin coatings of gloss have always shown less gloss, and useful results continue to be available with multiple thin coats.

And BTW, people having trouble with ink lifting during rolling will be glad to know that is greatly reduced with highly thinned varnishes.  Water is less a solvent that concentrated varnishes.

[philbaum]

Wow Bill t, you've tried lots of things.  Way to go.  One of my uncles was a chemist who assisted in the development of epoxy.  He'd be very amused to find that i was messing around with varnishes.  (Here's to you Stephan)

Anyway, I wanted to say that coatings are blends of various chemicals and solvents to achieve some specified performance levels. Is any of this stuff "sacred"?  Not in my opinion.  There are probably a lot of overlaps with how various ingredients, such as surfactants, the amount of thinning, etc., affects the coating performance.  I still have a few pieces from 2 years ago that i stretched and coated with polyurethane (in the reverse order :-)) that still look good.  On the other hand, as reported above, i have a test strip coated with a brand new product intended for inkjet printed photographs, thats 2 days old and still has pinholes in it :-(.

I suspect that the high prices associated with some products reflect the smallness of the art canvas market more than than the price of any of the ingredients.