optically clear adhesive scenarios:

[Dave Garrett]

Hello All, I have a customer who would like flourescent green acrylic adhered to a clear acrylic backer that will be part of a sign. There is a design element behind the acrylic that should show through the 2 acrylic layers. (it's astroturf. not my idea!)
Here's my question:
What is the least detectable, most optically clear adhesive option that you have used with success? We don't want to go the hardware route fyi.
My sci-grip weld-on #4 is so far is not getting the job done. Is there any sheet/roll material to apply before cutting that is optically undetectable?
Also, when using weld-on 4 do you use any pressure/weight/clampage of any kind?
would love to see what you guys have to say!

[John Lifer]

Just played with 3M 468 tape and it is clear, but you will see bubbles as bad as any weldon... Nothing is going to be perfect. Can you make a border around these two parts and glue there? Do a search, this has been brought up before.

[Mike Null]

I use weld on and can get perfect joints. It is difficult and my success rate is probably about 50%. The larger the area the less chance of a perfect result. Do not apply any pressure when bonding the two pieces. Do not starve the joint.

[Kev Williams]

I'm not sure how large an area you're doing or if tape is a must or what, but---

Loctite Go2 glue may work-
454130
--Best description I have is, it's like thinned clear silicone, even has a silicone smell to it. It's about the consistency of contact cement but without the 'melted cheese' effect. Maybe a bit thinner... It's sets in about an hour IIRC, but needs a 24 hour cure. I've used to glue glass awards and pieces of plex together, it's absolutely clear and never a bubble. It's holds very strong, but if you NEED to pull it apart, you can with some effort; like silicone, it remains flexible.