EPS Question

Posted: Mon Aug 28, 2006 10:57 am

Can someone give me acoustical coefficients of 1 lb and 2 lb polystyrene EPS foam?

I've got some other question about coating ESP with a couple of kinds of material.

I've used several materials over EPS, regular cement, a plaster compound called "One Coat" and another material called "MarbleTite"

When using white cement you can color it so it never needs painting and MarbleTite comes in many different colors.
Mable Tite is what it sounds like, marble dust and particles mixed with a cement compound.

I'm experimenting with an Architectural Foam company on some diffuser ideas.
They can cut anything foam in any shape with cad cutters.
You'll see some of their work when I post the finished pics of my room.

Uncoated can you give me some coefficients for EPS.
Thanks,
Larry

By the way I did a search on EPS and looked at Bobs coefficients page and don't see this info.

Posted: Tue Aug 29, 2006 12:06 pm

That's because Encapsulated Poly-Styrene foam is closed cell, and completely worthless for anything I can think of related to studio building; very low mass, so worthless for isolation, and you can't blow through it so it's worthless for absorption.

About the only use I could think of is cutting it into strips and building a very lightweight diffusor... Steve

Posted: Tue Aug 29, 2006 12:21 pm

I am using it for diffusion.
If I coat it it will take on a different property.

Maybe I could make something like sound blocks.

I see a lot of different acoustical products made from EPS. Or at least I thought it was EPS.

If it has no absorption properties does that mean the weight will make no noticeable difference in the product?
Thanks Steve,
Larry

Posted: Tue Aug 29, 2006 12:24 pm

omegaarts wrote:

By the way I did a search on EPS and looked at Bobs coefficients page and don't see this info.

That's because Bob has the annoying habbit to enter only sensible data on his page.

Thumbs Up

See Steve's reply ...

Edited: message crossed ...

For diffusers or Helmholtz or whatever, it's good to use the higher densities for mechanical strength.
I once cut Helmholtz ceiling tiles from them (via a specialized factory of course) to be used in very moisty circumstances (hall cleaning bottles in brewery = very high RH). I did it with 30 kg/m3 which is a rather dense quality for polystyrene (with enhanced fire properties).

Posted: Tue Aug 29, 2006 12:55 pm

why do I get the feeling you guys aren't real thrilled about EPS?

Thanks for the info.
Larry

Posted: Tue Aug 29, 2006 3:46 pm

Larry,

Take it outside and set a match to it. If you're happy with the results, continue. If not, either spray with some sort of fire-retardant material, or reconsider.

I once tried the flame test on "weedblock" which I thought was a fabric but turned out to be a finely perforated plastic. It ignited so fast and started melting flaming droplets, that it didn't take me long to reconsider.

All the best.

Lee

Posted: Sun Sep 10, 2006 9:44 pm

I had two 6' x 6' Sky line type diffusers made out of 2lb polystyrene.
This company makes sets for video and stage as well as water proof columns and shapes for outdoors. They have some kind of fire retardant and two coats of latex paint to match the room.
It's all CAD machines and lathes.

They sent two guys out and installed them for me too.

Total cost $638 including tax and installation.

Is that crazy or what?

The owner happens to be a guitar player and wanted to help out.
LH Razz

Posted: Sun Sep 10, 2006 10:07 pm

Larry, sounds interesting. Can you post a photo?

What are the dimensions of each of the columns and what's the max height?

What series did you use to come up with the pattern/s of columns?

What

Posted: Mon Sep 11, 2006 12:34 pm

I have like a half dozen 4' x 8' boards of that Pink OwensCorning EPS board that is 1.5" thick, and I don't know the density. I have been thinking recently about cutting them into strips and trying to make a Skyline-type diffuser out of it all. I can probably figure out how to stick them all together and maybe coat them with some fire retardant and reflective stuff, but I'm a little stuck trying to think of the best way to cut them. Will a table saw or band saw be too rough with it? Any other thoughts on doing this?

Posted: Mon Sep 11, 2006 2:26 pm

A table saw isn't bad, but the best way is with a cutter designed for the job. I forget what it's called but it's basically a thin, hot wire.

Posted: Mon Sep 11, 2006 2:49 pm

Yeah, that would be cool....a hot thin wire...Maybe I can rig something up. Twisted Evil

I guess even if I do cut it a little rough, maybe I can coat it with something that will hide the imperfections.

Posted: Tue Sep 12, 2006 6:58 pm

This is what works, if you can afford (or copy) it... Steve

http://www.demandproducts.com/hotknife.html

Posted: Sun Sep 17, 2006 6:50 pm

I tried using a hot knife and built a hot wire band saw. I was totally frustrated trying to keep it all working. When you are making presice cuts like in a skyline it's almost impossible to get it looking decent.
A real CAD hot-wire cutter adjust the temperature according to the line you are cutting. For instance, when you cut a 90 degree angle if the temperature doesn't adjust you'll cut right through the 90 and have to back up.
In a pro cutter the wire never touches the foam only the heat from the wire, which means if it doesn't adjust the temperature when you cut an angle the heat will burn past the angle.

I tried cutting with a real band saw and real fine jigsaw blade and believe me it's a total disaster If you don't care what it looks like it can be done to serve the purpose.
The diffusers I had made look better than than any skyline types I've ever seen.
I promise I'll post some pictures but I've been going day and night the last couple of weeks.

Hope this gives some insights too my experience home made hot wire cutters.

They are built on prime 157.
LH

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