curve-able translucent plastic

[kicknargel]

Hey folks. I'm building some translucent columns for my corporate rental inventory. For much of my translucent stuff I use Coroplast (corrugated plastic) but it won't make the bend without folding. I'm fitting the plastic into a 12" radius inside curve. I don't think any kind of fabric will work because it won't make an inside curve (it will tend to pull itself inward, out of round. I could probably use acrylic or polycarbonate, but am hoping to find something more affordable (I need 25 sheets).

Things I've looked at:

Diffusion gel: too flimsy
HIPS (high impact poly styrene, i.e. vacuform): too opaque
LDPE: too transparent
HDPE: haven't found an appropriate thickness

I just ordered a sample of Lee 400 (LeeLux) which is a thick diffusion. Maybe that's a winner, but I welcome other ideas.

[josh88]

I don't know if this is the best option for budget and ability but you might be able to do it with some clear acrylic and a heat gun. I had to make a clear column once and we had some of that sitting around so we cut the curve we wanted out of plywood. with a couple of those we made a little frame so it could lay down and we just hit the acrylic with enough heat to bend it over the mold. might be an option, and that's the only help I have since I've never worked with the stuff outside of that.

[Van]

My only two real 'go to' ideas for translucence are sanded plexi or applying drafting vellum to clear plexi. I hate white, milky plexi that they sell as translucent, looks horrible, IMHO. I'm not a big fan of Coro-plast either. I don't like the way the corrugation lines distrupt the light. In the past I've used a random orbit sander with 60 - 80 grit paper and just sanded the heck out of one of both sides of plexi. Works great. Our resident Scenic Designer taught me an 'Old School' technique of applying drafting vellum to the outside of windows on stage. it give a great quality and it's realtivly easy to accomplish with spray 77. you could also use rice paper or basting cloth for some intersting/different qualities of transmission.

[bdkdesigns]

I Never even thought of something as simple as vellum before! I too hate the white plexi and have always done the sanding route. That could have saved a lot of time on some projects.

[FatherMurphy]

Call an outdoor sign shop in your area, and see what they have as suggestions. There's lots of unusual plastics and vinyls that they'll be familiar with that nobody else will even deal with.

[Tex]

I'm doing something similar for Grease. I'm using panels for the recessed fluorescent fixtures they use in drop ceilings. We tested it and it took a very tight curve before cracking. About a 12" diameter if I had to guess. It has a textured pattern, but it's not really noticeable if you put the smooth side out.
Here's a picture of a very incomplete set...

[Van]

... I'm using panels for the recessed fluorescent fixtures they use in drop ceilings. We tested it and it took a very tight curve before cracking. ....

I'm amazed you got that much flex from them prior to cracking. Those diffusers are notoriously fragile and prone to breakage. Under the stress of tension I'm not sure how well they would hold up, long term. Since these are for rental stock I'm thinking something slightly more durable. On the other hand they are, relatively cheap.... Cool set btw.

[Tex]

I'm amazed you got that much flex from them prior to cracking. Those diffusers are notoriously fragile and prone to breakage. Under the stress of tension I'm not sure how well they would hold up, long term. Since these are for rental stock I'm thinking something slightly more durable. On the other hand they are, relatively cheap.... Cool set btw.

Thanks. It looks much better in the dark right now.
These panels were about twice the price of the brittle ones and about 100 times more flexible. I was able to cut them with tin snips without any cracking or shattering.

[Van]

AHA ! They're poly-carb then ! that's why !

[kicknargel]

Thanks, I'll look into those panels. If they're poly-carb they're probably pricey. Looks like they let plenty light through--do they also do a good job blending out the source (not too hot-spotty)?

[Tex]

Thanks, I'll look into those panels. If they're poly-carb they're probably pricey. Looks like they let plenty light through--do they also do a good job blending out the source (not too hot-spotty)?

They do a very nice job of blending out the source. The columns in the picture have an LED par top and bottom. The stairs have an LED strip under the first step pointed at a white luan reflector on the legs. The set is going to be a large jukebox (I know, cliche but the kids are excited about it). I think the light boxes will be a reasonable neon facsimile. We just have the 16'x10' arch left to do.
The panels are just shy of 2'x4' in both directions, but I believe you can order them in 6' and 8' lengths as well. They were about $9/ea. at Lowe's.

[kicknargel]

I feel a little stupid. None of us had tried bending the Coroplast against the grain. Seems to work. Great optical properties, and ~$10/sheet. And if we need to we can heat it a little in the vacuuform.

[Robert]

I used Lexan and painted the inside with clear flat sealer from Rosco. I used a spray gun and made several passes to get heavier ammounts of diffusion. I actually made a series panels with different ammounts of diffusion. I tried the heat gun, sanding and, and solvents but got the best results from spraying.

[65535]

Any thermoplastic can he heat formed, lightly heating the plastic can help you form it and it will set in the shape you leave it in. Sandblasting leaves a wonderful surface finish for diffusion.

Acrylic is very brittle, polycarbonate (trade name Lexan) can be used for a number of things and by using different thicknesses you can customize the way it behaves when bent.