Hi Phil, A variety of factors can contribute to warping of foamcore panels, especially when freely hung as you describe. First and foremost, when you apply graphics to the foam core panel, do apply a 'balance sheet' on the reverse side? When you laminate or dry-mount digitally printed graphic material to only one side of a foam core panel you alter the expansion and contraction characteristics of the panel. The laminated side will expand and contract from thermal changes as well as humidity changes at a different rate than the back side in the absence of a balance sheet. In addition, different mounting methods such as spray mount, sheet adhesive, etc. can shrink and expand as they cure over time, the effect is what is often referred to as 'potato chipping,' for obvious reasons. It is always best to match the front and back in terms of material, weight of material, and method of lamination. If you apply a protective clear laminate over the graphics, apply it on the backside as well. Now you also have another factor that comes into play here - thermal dynamics. I have often seen panels suspended in historic houses or galleries from picture rail that are 'potato chipping,' even when they have a balance sheet as I just described. Why? Because of the temperature difference between the side facing the wall and the side facing the room. In some cases, like historic houses with plaster walls, this warping is exacerbated by humidity migrating from the plaster walls or masonry to the backside of the panel. Using balance sheets and clear overlay will help in this case because the clear sheet provides a 'barrier' of sorts and the expansion of the material may not be as severe as an unprotected panel. If you want to see a severe example take a sample panel and lean it up in a window and watch what happens. Another factor is the foam core itself. Different materials act in different ways. Basic, inexpensive foam core material is faced with paper and is prone to warping. Other types that are a little more expensive use more stable materials - for example "Gator Board" which uses a wood fiber based veneer or as you noted, synthetic products such as Sintra. Bear in mind that in addition to the escalating costs of these products, the handling, cutting, and hanging of them involve more effort. Sintra or its equals is significantly heavier than traditional foam core products. Here's a tip from the low cost toolbox that I've used in the past. Use a painted hollow panel that you either fabricate or adapt from a 1 3/8" thick hollow core door as the substrate and then laminate your graphics (using a stripable adhesive or, I have had them directly printed to adhesive vinyl film) to this more stable panel. You'll end up with a nice, frameless, contemporary graphic panel. When you are done with the exhibit you can remove the laminated graphic, paint if needed, and recycle the panel by applying new graphics. Good luck! Larry Fisher Museum Planner, Designer, Imagineer 6 Belvedere Drive Bristol, Rhode Island 02809 p:(401) 253-5335 e: [log in to unmask] On 1/26/2011 12:43 PM, Phil Raino wrote: > Hello all, > > Our library's exhibits invariably incorporate informational panels, > ranging in size fro 24" x 36" to 48" x 72", digitally printed and > mounted to foamcore. These mounted panels get hung within wall cases, > or via chain from a hanging rail on walls. I've run up against a > persistent problem with some batches of foamcore exhibiting notable > warping and bowing (depending on the season as well). If indeed > similar panels are being used by you all in your exhibits: By what > methods, or with which products, can these panels be kept rigid and > flat, minimizing or even eliminating the bowing? > > The most obvious answer is putting the panels within oversize picture > frames, but this results in... well, a distracting frame around the > panel's graphics. Experiments with adhering unglassed picture frames > to the backs of the foamcore panels have been less than successful. As > we've no fabrication facilities on the premises, I've not been able to > make wooden frames or supports. > > Is it simply a question of opting for the much-more-expensive Sintra > or another material that isn't as warp-prone? > > > Phil Raino > Exhibits Developer, Special Collections Research Center > The Estelle and Melvin Gelman Library > George Washington University > > ========================================================= Important > Subscriber Information: > > The Museum-L FAQ file is located at > http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed > information about the listserv commands by sending a one line e-mail > message to [log in to unmask] > <mailto:[log in to unmask]> . The body of the message should > read "help" (without the quotes). > > If you decide to leave Museum-L, please send a one line e-mail message > to [log in to unmask] <mailto:[log in to unmask]> > . The body of the message should read "Signoff Museum-L" (without the > quotes). > ========================================================= Important Subscriber Information: The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes). If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).