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We just finished some routered aluminum faces with clear "push thru" letters. The faces of the letters are covered with translucent Silver vinyl, with the edges remaining clear. There are thousands of dark spots visible in the glue layer when viewing the letters from the edges.
Materials used: 1-inch thick optically clear acrylic FCO letters bonded to a 3/16-inch sheet of 7328 White acrylic. Glue used was a 50/50 mix of Weld On 3 and Weld On 16. Letters were weighted after gluing.
Anybody had this happen before?
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Brad in Kansas City signbrad.com
-------------------- Brad Ferguson See More Signs 7931 Wornall Rd Kansas City, MO 64111 signbrad@yahoo.com 816-739-7316 Posts: 1230 | From: Kansas City, MO, USA | Registered: Nov 1998
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Looks like the adhesive melted onto the edge. You did cut it with a down bit right. Normal would be vertical chatter marks
-------------------- John Arnott El Cajon CA 619 596-9989 signgraphics1@aol.com http://www.signgraphics1.com Posts: 1443 | From: El Cajon CA usa | Registered: Dec 1998
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I was told these were not router cut, John. They came from Gemini, so I am assuming waterjet cut.
The spots are not on the edges but in the glue layer between the 1-inch clear letters and the 3/16-inch white backer.
They look like air pockets in the glue to me, but the employee claimed he had good capillary action between the two surfaces during the gluing process, though I did not watch the glue-up. Good capillary action should have rendered an even layer of solvent glue between the surfaces, nearly invisible, in my opinion.
Had the letters not been clear, this probably not would have been an issue. I don't know why 1-inch white acrylic was not chosen for the letters. I wasn't in on the planning of this one. It is a very expensive sign on which to be experimenting with untried methods.
-------------------- Brad Ferguson See More Signs 7931 Wornall Rd Kansas City, MO 64111 signbrad@yahoo.com 816-739-7316 Posts: 1230 | From: Kansas City, MO, USA | Registered: Nov 1998
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I'm having trouble understanding your photo, sorry.
Why did you mix the two glues?
I use straight methylene chloride to glue acrylic together if it is a wide area, close capiliary action fit. I use Weldon when there are gaps to be bridged or fillets to fill.
Have you tried to melt the bond apart (or break it somehow) and sand the faces smooth, and reglue them?
Why did you choose optically clear acrylic when it was going to have a vinyl face and a white back end?
If you mixed the 2 glues, I'm suspecting airbubbles were inadvertently stirred into the mix while they were being mixed. Somehow you then got 'solvent pop' happening in the tiny airpockets stirred in, after they'd had time to think about getting even with you!
[ September 24, 2015, 09:12 AM: Message edited by: Ian Stewart-Koster ]
-------------------- "Stewey" on chat
"...there are no limits when you aim for perfection..." Jonathan Livingston Seagull Posts: 7014 | From: Highgrove via Toowoomba, Queensland, Australia | Registered: Dec 2002
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My remedy suggestion is go and buy an aerosol can of white acrylic lacquer- automotive grade - put the letters face down, to protect the silver vinyl, and fog a mist-coat of white acrylic lacquer over the letter sides.
If you can keep it an even dusting, then when it's all switched on, it'll look barely any different from 'normal'.
-------------------- "Stewey" on chat
"...there are no limits when you aim for perfection..." Jonathan Livingston Seagull Posts: 7014 | From: Highgrove via Toowoomba, Queensland, Australia | Registered: Dec 2002
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quote:I'm having trouble understanding your photo, sorry. Why did you mix the two glues? I use straight methylene chloride to glue. I use Weldon when there are gaps to be bridged or fillets to fill.
Have you tried to melt the bond apart (or break it somehow) and sand the faces smooth, and reglue them?
Why did you choose optically clear acrylic when it was going to have a vinyl face and a white back end?
If you mixed the 2 glues, I'm suspecting airbubbles were inadvertently stirred into the mix while they were being mixed. Somehow you then got 'solvent pop' happening in the tiny airpockets stirred in, after they'd had time to think about getting even with you!
Ian,
The close up picture is confusing. I don't know why our fabricator mixed the two glues. I agree that only the water consistency Weld On #3, which is mostly methylene chloride, should have been used by itself. Mixing the thick #16 with the #3 probably negated any chance of good capillary action. I, too, suspected that stirring the two introduced bubbles.
Why were the letters ordered in clear? Very good question. I believe they should have been white. At the very least, the process should have been tested.
I was not really involved with this job till I was asked my opinion when it messed up. I am curious to see what they do to fix it.
-------------------- Brad Ferguson See More Signs 7931 Wornall Rd Kansas City, MO 64111 signbrad@yahoo.com 816-739-7316 Posts: 1230 | From: Kansas City, MO, USA | Registered: Nov 1998
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i agree with ian.. The mixed glue was too thick to allow for the complete capillary action.
I do not believe one can take the glued pieces apart. The solvent melts the plastic so they can combine into one.
I use pure methylene chloride to seal up plastic. IT is perfect for building aquariums because the seal is invisible.
-------------------- Leaper of Tall buildings.. If you find my posts divisive or otherwise snarky please ignore them. If you do not know how then PM me about it and I will demonstrate. Posts: 5273 | From: Im a nowhere man | Registered: Jul 2001
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In theory, the faces are stuck forever, but I have been able to separate two seemingly bonded faces, back to their most of their former alter-egos, on occasions, after a day of them sitting around...
You think the innermost parts which have been bonded are as set as the outermost parts, but often the glue might be still invisibly wet, and not yet firmly bonded in.
In other words, I have successfully undone a stuff-up, and fixed it, when it appeared all was lost... though theoretically I should not have been able to separate the faces. It was an interesting exercise, and I learned a lot - particularly not to assume all apparently well-bonded surfaces were actually so...
When you get some spare time, it is worth experimenting, to see just how good a bond you can get, and what it takes to split it. Use some MeCl to glue two bits of 10mm clear acrylic, and when you think it's set, attack the side of it with a hammer...
[ September 25, 2015, 02:07 AM: Message edited by: Ian Stewart-Koster ]
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"...there are no limits when you aim for perfection..." Jonathan Livingston Seagull Posts: 7014 | From: Highgrove via Toowoomba, Queensland, Australia | Registered: Dec 2002
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-------------------- Brad Ferguson See More Signs 7931 Wornall Rd Kansas City, MO 64111 signbrad@yahoo.com 816-739-7316 Posts: 1230 | From: Kansas City, MO, USA | Registered: Nov 1998
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