Bubble Bubble Toil and Trouble

Broken Circle / Bubble Memory No. 3

Who hasn't had bubble problems when mounting pictures?

That old gremlin paid us a visit again this afternoon at Vashon Island Imaging. A beautiful waterfall panorama by Kirk Beeler (see second picture below) was ruined by bubbles during dry mounting onto a prefab frame. More than disappointed, I was flabbergasted when I took it out of the dry mounting press and saw the problem (shown below).

Not a pretty picture... trapped bubbles of gas have prevented lamination of the giclée with the surface if the mounting board. Ironic that a waterfall picture's demise should be the water cycle itself, eh? Life's little practical jokes.

Flabbergasted is a ten-dollar word that you don't get a chance to use that often. This time the word was more expensive than that.

We dry mount all the time on all kinds of materials. Our trusty mechanical Seal® presses have served well. One has been in my service more than 40 years... now that's quality. So it's not like I never did dry mounting before.

Today's problem recalled a similar incident last summer when one of our clients bumped into the same issue mounting onto MDF (Medium Density Fiberboard). She was not her normal 'bubbly' self after that. It's no fun when a 72-inch giclée gets trashed, for any reason.

Bubbles are made of trapped gas. The question is... where did the gas come from? In our case today, the frame board became the most likely suspect immediately. We had previous experience with all the other materials involved in the mounting. Epson® Premium Luster Paper and Bienfang® Color Mount® Dry Mounting Adhesive. That dry-mount tissue's melt point is 190° F (88° C).

Every new material brings with it problems... er, challenges. They are another reason why the phrase 'cost of doing business' was coined. Dare I admit that part of the challenge can be operator error? I should have had my headlights on when I saw the new kind of frame.

Actually, it wasn't a frame at all. It was an American Easel Wood Painting Panel . Our client brought it to us after sourcing from www.dickblick.com. It's a beautiful and affordable product made of 1/8-inch birch... so called 'Baltic Birch'. That's the light colored wood associated with Swedish architecture and furniture... beautiful stuff.

Baltic Birch is the same material we use to make our Spinning Calendars (www.spinningcalendars.com). For that project I had done enough research to know that this material comes primarily from Eastern European sources and has no consistent quality. There is a rating system of sorts but how can you know?

At issue are visible and invisible faults in Baltic Birch products. The visible ones are knots and other normal wood defects. What you can't see is what is in the middle of this thin, three-layer plywood, used frequently as veneer. What was used to glue the nice wood together? See where this is going?

Even though I know that, I didn't follow the basic rules of dry mounting. Pilots have checklists for this sort of thing. Here's my try at one for giclée people. (Now if I can just remember to use it religiously....)

Checklist for Dry Mounting

1.) Warm up press to operating temperature recommended
2.) Pre-dry materials in the press to reduce moisture
3.) Use release paper
4.) Apply enough pressure
5.) Cook long enough for all materials reach temperature
6.) Cool under weight (avoids separation and curling)
7.) Avoid flexing until totally cool

Press Warm Up

Vacuum presses are usually set 10 degrees lower. Is the thermostat and temperature gauge working properly? Does the vacuum suck?

Pre-Dry Materials

You've been to the tropics, right? So you know what happens to a nicely pressed suit. It becomes a victim of the water cycle.

Everything that isn't oil or resin based is part of the water cycle. Water passes through many of the materials used to mount and frame giclées. Wood and paper products absorb water from the air, or release the water they contain back into the air (drying) depending on factors like temperature, humidity and altitude. You've heard of the 'dew point'? This is like that.

Waterfall by Kirk Beeler

There are many ways to get water out of materials. The primary ones are vacuum, heat, pressure, and air circulation (breathing). The hard part is, knowing if you succeeded. Bubbles are a sure sign that you didn't.

My rule of thumb is that if the materials in the press are as hot as the press that is enough. That said, it might take some time for complete escapement of water from thick materials.

Curiously, and possibly coincidentally, the problems with MDF referred to above occurred when using 5/8-inch (16 mm) thick boards ...and the bubbles in our print were over the frame, which is more than an inch (25mm) thick. Furthermore, our client had painted that part, effectively sealing out any water escapement through the back of the piece.

Notice that the bubbles occur right over the thicker frame parts beneath the 1/8-inch surface plywood.

There is every possibility that I didn't cook the frame long enough... but it will take another try for that theory to be tested. My suspicion is that it takes a good long time for the water to escape from thick materials like MDF and 1X2 anything.

The reverse side shows the black-painted frame that supports a 1/8-inch (3mm) thick surface of Baltic Birch plywood. Notice how a support made of gray mounting board and two strips of 1X2 cedar have been inserted to keep the thin plywood surface from bellying under the pressure of the dry press. That is exactly what happened on the first try. Grrrrrr.

Release Paper

Kraft paper has always been my most used release paper... normal Kraft paper, not the exotic colored kinds sold under that name. We're talking about plain paper with no additives... like brown-paper bags. That kind of paper has the right qualities for a release paper. It is heavy enough, breaths, and is cheap to replace when you eventually screw up.

Paper towels are another favorite, especially when working with Epson® Premium Luster Paper. The surface of that paper is less durable and more sensitive than you think, being particularly subject to abrasion and 'micro' abrasion. That's because this paper has a harder surface than matte papers, so the ink sits on top instead of absorbing into the paper.

Even after a week of drying Luster prints are still -- and will always be -- sensitive to scuffs, finger printing and general marring... unless coated or covered.

Giclée prints need several days (minimum) to dry. We originally started using paper towels when stacking Luster paper giclées for drying. Epson® recommends 'plain' paper ...but what is that? Anyway, you wouldn't use copy paper to mop-up spilled coffee, eh? So when it comes to absorbing things I leave it to 'The Quicker Picker-Upper'’.

Evaporation and Percolation

Water in the inks evaporates while the glycerin content percolates into the ground on the substrate. It's the percolation that takes time. To be technically correct, the evaporating water carries off a certain amount of the glycerin. I have heard this referred to as 'expungation' but that isn't an actual word.

If you frame a giclée in glass or Plexiglas® before the percolation and evaporation are complete, the expunged glycerin is electrostatically drawn to the cover glass or plex and makes the picture look dusty...from the inside. You have to take the whole thing apart to clean the glass.

To avoid those problems we make it a practice to dry Luster prints before mounting or framing or anything. But did I do that this time? No, because it was a rush job. Hence the expression, 'haste makes waste'.

Take A Breather

'Breathing' is important for release material. Remember the gas? Papers that breathe readily absorb and release water... it's the 'water exchange cycle'. Artificial materials are watertight, however. They can trap gas because water vapor can't pass through.

Artificial materials like silicon and Teflon® are another matter altogether. Various sorts of release paper and release board made of these materials are available, although pricey. These are necessary if the print you are mounting melts under the dry press heat. Laser printing toners come to mind. If you use Kraft paper the laser print toners will melt into it creating a permanent bond between them that is as good or better than the dry mount tissue. Not exactly what you want in a release paper.

The absolute best release paper I have ever encountered is that shiny brown paper that comes in packs of Epson® Premium Luster Paper. Epson should sell rolls of that stuff because nothing will stick to it, not even laser printer toner. I would order a roll here and now if I could. (If you have any you aren't using, send them to me!).

Pressure Cooker

Using a mechanical press, a certain degree of force is needed to create sufficient pressure for good bonding. The force of steam is incredible. Steam used to drive locomotives for goodness sake. If any steam is present, it takes a lot of pressure to it from lifting the giclée away from the mounting substrate.

If you have a new press it may have enough ooomph. After time that dissipates, requiring an assist, or an assistant. We use a 25-pound (11.3 kg) sandbag and hang it from the press handle with a hook and some rope. Pretty basic, but it works and provides consistent pressure every time. It's easy to swap weights, too, if more or less is needed.

Raising the base under the mounting 'sandwich' is another way to increase pressure, especially when you reach the limit of the handle's travel arc, as happens in older presses. We have some pre-cut pieces of 1/4 inch (6mm) Masonite® that we use as shims when extra pressure is needed. Together, the sandbag and shims do the trick and really put some squeeze into things.

If you are using a vacuum press about all you can do is make sure the sucker is working right.

Cook It Long Enough

Use the same rule of thumb as above... when the materials in the 'sandwich' you are cooking come up to the same temperature as the press, that is enough. Err on the longer side. Following are the guidelines provide by Bienfang®.for mounting a 16 X 20...

● 1/4-inch (6mm) Foam Board 2 minutes
● 50-80 Pt. Card Board 3 minutes
● 1/8-1/4 inch (3-6mm) Masonite® 4 minutes

You can see from those guidelines that a substrate's density and thickness both play roles in the timing. Denser and thicker substrates need more time.

Now, remember the MDF problem? That stuff weighs a lot, an indication of its extreme density. I wouldn't be surprised if 20 minutes or more weren't needed for that to set properly. A piece that is 1-inch (25mm) thick might require a half hour to come up to press temperature.

Cool Under Pressure

No, don't put a weight in the middle and call it done. The weight needs to be distributed evenly over the entire surface of the mounted giclée. That is the job of a cover sheet.

Cover Sheets

Cover sheets should be rigid, have some weight, and transmit heat to cool the hot-mounted giclée efficiently while keeping it flat. The perfect cover sheet would be 1/4-inch (6mm) plate steel or aluminum. A much less expensive solution is pegboard... Masonite with holes in it. That and a couple of sandbags is all you need.

If I am only mounting one piece, I just switch off the dry press and let the giclée stay in there while the press cools. That's the safest way of all because you avoid the risk of delamination, resulting from flexing.

Flexing Isn't 'Cool'

The temperature activated adhesive in dry mount tissue isn't set until it has cooled. After it has set, that is that. There's no re-melt option because dry mount tissue only works once. That explains why no amount of putting it back in the press will solve certain adhesion problems, especially those caused by bubbles or 'layers' of trapped gas.

Flexing isn't ever very cool though, even if the print is. Mounted giclées should never be flexed because any flexing starts the process of delaminating. Huh?

To understand what happens try this simple experiment. Get three like sized sheets of paper, copy paper for example. Arrange them neatly into a stack and staple them together at one end. Now, roll them up. On the other end they seem to have become three different lengths although they are actually equal. That is because the innermost layer is arcing tighter and smaller diameter than the other two, and the outermost larger.

If the layers are glued together to keep them from shifting, they resist bending (hence, plywood). If forced to bend by flexing the layers must by the laws of nature either de-laminate or disintegrate.

Underlays Prevent Flexing

To avoid these problems simple place everything on an underlay sheet sufficiently rigid to provide support during handling... like a flat baking sheet or just a piece of cardboard. Note that varying the thickness of this support can have an effect on the total squeeze pressure exerted when the press is closed.

Why Stick With Dry Mount?

You might ask, 'if dry mounting is so finicky, why not just use glue?'

That is a fair question requiring answers too long and detailed for a blog, even an epic-length one like this... which is why my book Giclée Prepress - The Art of Giclée is available at www.gicleeprepress.com. That said...

We are experimenting at this very time with alternative ways of synthetic 'paper' like Epson®'s Premium Luster. As noted in earlier blogs and my book, 3M® Repositionable Mounting Tissue works well but is too expensive, at $1.50 per square foot (0.093 m2). Spray is easy to use but produces enormous amounts of sticky 'dust' that gets everywhere. Do it outside? Are you kidding? Anyway, the jury is out on long-term adhesion of spray mount products.

Keep your eyes 'glued' to this blog for more news on this 'sticky' issue.