posted
I have 2 Sign foam signs (30" X 55") glued to a 3/4" plywood center, for strength (sign is between to brick pillars)the paint keeps blistering on the top, my guess is the screws into the plywood are drawing in moisture. I removed the sign last year and sealed everything with PB's Hardcoat, repainted & re-installed. Well the paint is blistering again, I'm thinking of maybe an epoxy coat on the top of the sign? Any suggestions would be greatly appreciated. Thanks
-------------------- Bruce Crawford Crawford Sign Co. 9217 Bechtel Road Elyria, Ohio Posts: 69 | From: Elyria, Ohio USA | Registered: Jan 1999
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This is just an educated guess, but I'm wondering if all the glueing, sealing and hardcoating is actually causing the problem by trapping moisture?
On various sandblasted projects I've done over the years, it has been advantageous to let things 'breathe'...
Sounds like somehow the plywood is absorbing moisture from somewhere. If it cannot evaporate, it will find other ways to get out, and/or it could cause the wood to swell.
posted
Not being mean but, why would anyone use something that will expand/contract, hold moisture, outgas, and potentially rot inside an HDU sign? I use only aluminum extrusions in my HDU signs and have never had a problem.
-------------------- Wayne Webb Webb Signworks Chipley, FL 850.638.9329 wayne@webbsignworks.com Posts: 7403 | From: Chipley,Florida,United States | Registered: Oct 1999
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posted
I must agree with Wayne Webb and I would like to hear the answer on why would anyone use something that will expand/contract, hold moisture, outgas, and potentially rot inside an HDU sign.
-------------------- HotLines Joey Madden - pinstriping since 1952 'Perfection, its what I look for and what I live for'
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Same here. Aluminum or steel. I like steel just a bit better because I'm not set up to weld aluminum.
Years ago, I took the advice of a Letterhead that said to use MDO plywood as a backer for HDU. I learned my lesson on that sign and went to aluminum or steel and haven't had any problems since.
-------------------- Dave Sherby "Sandman" SherWood Sign & Graphic Design Crystal Falls, MI 49920 906-875-6201 sherwoodsign@sbcglobal.net Posts: 5396 | From: Crystal Falls, MI USA | Registered: Apr 1999
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posted
I'd strip the edge, and brush in some West System (wet) 2 or three coats while it sinks in. Level it out with 407 or 410 fairing, sand smooth, and paint.
If you're fastening into the MDO, put some WS into the pilot hole.
I know that the SF guys don't recommend MDO as a backer - but I've been doing it for over 20 yrs without a problem. Just be sure to seal all exposed areas.
-------------------- Steve Purcell Purcell Woodcarving & Signmaking Cape Cod, MA
************************** Intelligent Design Is No Accident Posts: 900 | From: Cape Cod, MA | Registered: Oct 1999
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posted
For years we used MDO without any problems, but then began to see our signs warping and some hairline cracks in the edges of those that had MDO sandwiched between two layers of HDU.
We now use aluminum or DiBond. Some use steel because the guy that does our frames, brackets and such does not work in aluminum. Lots of primer and paint keeps everything from rusting.
I was probably that guy that gave the advice...and it was good advice at the time, but something must have changed in the MDO, adhesive, or paint....or a little of everything.
[ May 03, 2010, 01:41 PM: Message edited by: Raymond Chapman ]
-------------------- Chapman Sign Studio Temple, Texas chapmanstudio@sbcglobal.net Posts: 6306 | From: Temple, Texas, USA | Registered: Nov 1998
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posted
do not put something together that will rot with something that won't.
we use a webbing and gorilla glue to glue 2 peices together with and aluminum for edges were hardware will go through to prevent taring. i have found this the most superior way and it will not break. we did a sample at the shop then jumpped on it..no breaking!
-------------------- Dirk Rampling Far South Design South Pambula NSW Posts: 39 | From: South Pambula NSW Australia | Registered: Jun 2008
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PL Premium Urethane Construction Adhesive for urethane to urethane construction. Sometimes I'll finish assembly on support structure after all painting has been done. In that case I'll dribble some water and GG into the holes and allow for expansion to fill in the gaps before sealing with caulk. From this angle, you can see the 1/8 x 2" flat steel is unfinished and ready for the final assembly. I don't have pictures of the final assembly to post.
-------------------- Mike gatlinburg Sign Crafters Posts: 1051 | From: Gatlinburg, TN | Registered: Oct 2005
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Answer to Dick: West System Epoxy. Scuff up the DiBond and make sure all the dust is off the HDU. Apply epoxy to both side and assemble. We just put a bunch of gallon paint cans on top for clamps until the epoxy sets up.
-------------------- Chapman Sign Studio Temple, Texas chapmanstudio@sbcglobal.net Posts: 6306 | From: Temple, Texas, USA | Registered: Nov 1998
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-------------------- Dirk Rampling Far South Design South Pambula NSW Posts: 39 | From: South Pambula NSW Australia | Registered: Jun 2008
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As you know, Gorilla Glue expands making difficult to use on large flap panes. You'd need to apply considerable pressure to keep it flat.
I agree with Chappy about the use of epoxy. However there is precious little difference, if any, between West epoxy and other brands. Your local hardware is likely to have just what you need.
Of all the brands I've tested, MAS is the one I prefer because it's low VOC'swww.masepoxies.com/
[ May 06, 2010, 06:16 AM: Message edited by: Joe Crumley ]
-------------------- Joe Crumley Norman Sign Company 2200 Research Park Blvd. Norman, OK 73069 Posts: 1428 | From: 2200 Research Park Blvd. | Registered: Sep 2001
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