Edge-lighting a piece of glass that has sand carved graphics can look pretty cool. We have recently tried the same technique for acrylic with disappointing results. When edge-lit, noticeable flaws appear in the acrylic — little hot spots that appear to be tiny pits or bubbles. We have tried three different sheets of half-inch clear acrylic with similar results. One sheet even exhibited what appeared to be wide roller marks, from the production process, I assume. Has anyone successfully edge-lighted half-inch acrylic?
Brad in Kansas City
Posted by Ian Stewart-Koster (Member # 3500) on :
I've fiddled a little, and looked at lots, and haven't see what I'd call a fault in any. One not-so-obvious trick is to seal or cover the three edges not lit, with white vinyl, so they help to bounce the light around inside, more. The lit edge needs to be polished to transparency, or flame polished. The other three edges stay frosty white, plus extra white vinyl.
Posted by MozeCollins (Member # 51014) on :
It sounds like you might have used extruded acrylic rather than cast.
Posted by Bill Davidson (Member # 531) on :
We had a sheet of clear Only used for edge lit, the expensive stuff. Costs less to make one than make one over and over.
Posted by Brad Ferguson (Member # 33) on :
Thanks for the replies.
I think we have sheets that are extruded, rather than cast, acrylic, as Mose suspected. The barely visible footprint from wide rollers is the giveaway. Our supplier was clueless about the manufacturing processes for acrylic. They thought acrylic was acrylic.
Cast acrylic is literally cast as a molten liquid, about the consistency of syrup, into molds, in one of two ways. "Cell cast" is made in sheets in a mold made of two sheets of glass with gaskets at the edges. "Continuous cast," a less costly production method, is done when the molten mixture is cast between two continuous sheets of polished metal in much longer runs as it goes through a series of heaters for curing. Again, gaskets seal the edges. Additionally, cast acrylic is polished. Cast acrylic is known for optical clarity. It is also more heat resistant, which is why cast acrylic cuts so much cleaner when machined, whereas extruded acrylic tends to melt behind a sabre saw blade.
Extruded acrylic is a less costly process and provides, no doubt, the larger share of acrylics used in the sign industry.
Acrylite FF is an example of an extruded acrylic. Acrylite GP is cast.
Airplane and helicopter canopies are made from cast acrylic because of its optical clarity. Plastic sign faces are mostly extruded acrylics.
Brad in Kansas City
Posted by MozeCollins (Member # 51014) on :
Do I win any burnt ends from Arthur Bryant's? Posted by Gary Boros (Member # 8487) on :
So Brad, have you had the opportunity to try your edgelit sign with the cast acrylic? I've been wanting to try an edgelit myself but haven't had a chance to do so. Are we saying here now that only cast acrylic is suitable for edgelit signs?
Posted by Brad Ferguson (Member # 33) on :
Moze, Obviously, you've eaten barbecue in Kansas City. Arthur Bryant's sounds real good right now. But at the risk of being pilloried by my cowtown neighbors, I think I like Memphis barbecue better. When I lived in Arkansas, I always noticed that when crossing the bridge from West Memphis, Ark., into Memphis, the oncoming drivers all had grins on their faces. I eventually realized it was because of Memphis barbecue. I wish barbecue weren't so expensive. But then I would just eat more.
Gary, I was not really involved with this job, but I found out today that since my boss did not resolve the problem at the time, even after talking with our acrylic suppliers (Regal Plastic and Laird Plastics both sent reps to our shop to look at problem), he simply nixed the idea of using acrylic altogether and bought 1/2-inch plate glass instead. It is now a VERY heavy edge-lit sign, and we didn't even try using cast acrylic. So, in answer to your question, I don't know if cast acrylic is suitable for edge-lighting or not, but extruded acrylic is definitely not.
Brad
Posted by MozeCollins (Member # 51014) on :
Yes sir, Brad. Have been there multiple times and enjoyed a slew of bbq from a few of the places up there. But I definitely agree...Memphis bbq is pretty great.
Gary, if you're doing edge lighting, you want cast. Extruded won't transmit light as well and the lighting will show more 'flaws' in the material.
Posted by Curtis hammond (Member # 2170) on :
paper liner usually means cast. Plastic liner usually means extruded,
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