Tape on acrylic

[Rick Maitland]

Hello all,
I am getting ready to do a large 34 x 18 all acrylic sign hung inside a customers garage. The sign will be 2 layers. The bottom layer will be 1 solid piece of 1/4". The top layer will be many 1/8" thick pieces. My question is would it be OK to use double-sided tape for bonding, and if so then which type might you recommend? The tape will have to put up with very hot temps. Most of the top layer is going to be mirrored and when using the acrylic glue I get a "cracked spider web" look when it dies. My guess is that the glue is eating through the mirror layer. We have samples coming from 3M but I wonder if any of you have given this a shot. I will post pic.'s when I get it done.
Thanks

[Mike Null]

If you give 3M the requirements they'll guide you to a tape.

[Dave Fifield]

The cracked spider web finish comes from the fact that you are using too much acrylic glue - the spidering happens as the excess glue evaporates. Make sure the pieces to be joined fit perfectly, then, butt them up to each other using a jig to hold them in place, then run the acrylic cement into the joint, being careful to a) do it fast and b) use it very sparingly.

Dave Fifield

[Keith Outten]

Get a tube of Loctite adhesive or you can use silicone adhesive either one should do the trick and prevent damaging the mirror backing.

I recently bought a caulk tube of Loctite adhesive to bond Corian moulding to ceramic tile, it is bonded forever. The Loctite adhesive is thinner than silicone and might be easier to keep the coating consistant. I would use a brush to apply it, in fact I have a simular project in my shop right now.

.

[Joe Pelonio]

You can't use acrylic cement on mirror. Silicone and other adhesives might work but there's a cement made for this that will not chemically react to the mirror back or the acrylic. Liquid nails makes a mirror adhesive, also Bostik and others. You should find it at better plastic suppliers and glass shops.

If you do prefer DS tape look at a sign supply for what they call "Banner tape". It's clear, very thin but easy to apply and strong, and can take the heat of full summer sun. I keep rolls of it here all the time for mounting engraved signs, laminating plastics together and sometimes even for banner edges.

[Rick Maitland]

Thank you all for the help. Last night I started out by bonding 2 scrap pieces of acrylic together using the tape sample that 3M gave us. I could NOT pull it apart. I applied the tape to the back and gave it a go. With 1/4 " mirror my settings were 100P 3S 35W and I still could not get all the way through the back side of all areas of the tape. 2nd go at it I tryed cutting with the tape side up..... BIG mistake. After running it at that same speed and power 4 times I still was not through and I had a big gooy mess. I ruined a 12x24 sheet of mirror :( . I also cleaned the top 2 mirrors and the lens but that did not help. I am going to check the bottom 2 today. My thoughts are that maybe the adhesive in the tape is heating up and running down into the cut? I am also now concerned with having the lens in there upside down. Does this make a diffrence? I remember my Rep. telling me something about being able to see your reflection in the lens, but was that looking at the top of the lens holder or at the bottom :o. If I can get through these problems then I think I will finally have something worth posting pic's of. Wish me luck!!

[Rodne Gold]

Why are you trying to cut thru the tape with a laser?
Surely you cut both layers seperately and then apply the tape and bond the 2?
If positioning of one cut layer on the other is a problem , just outline where the top layer is supposed to go with a vector line and run it at very low power , you will get a positioning hairline.

[Rick Maitland]

Why are you trying to cut thru the tape with a laser?
Surely you cut both layers seperately and then apply the tape and bond the 2?
If positioning of one cut layer on the other is a problem , just outline where the top layer is supposed to go with a vector line and run it at very low power , you will get a positioning hairline.

I am appling the tape first because the top mirror layer has many curves ( flame design ) and would be to hard to cut the tape by hand after the acrylic was cut. Do you know of a better way of doing this? This will be my first time to use tape, or should I even be using tape at all?

[Joe Pelonio]

I wouldn't try to cut through the tape at the same time either. All you have to do is cut the mirror, then cut do a -1/16" countour on the artwork and cut the tape by itself. Masking tape the edges onto some card stock if you have to to keep it flat.

[Rodne Gold]

If you use the 3m VHB tape , you wont need a lot of it and you can easily cut small pieces , The tape is called ISOTAK here in south africa and we buy it in 1/2" wide rolls , a little goes a LONG way. Its almost like a clear jelly with a brown backing.