Author Topic: Extruded vs. Expanded Polystyrene for Benchwork  (Read 5415 times)

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Matthew Roberts

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Extruded vs. Expanded Polystyrene for Benchwork
« on: August 03, 2008, 12:38:54 AM »
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What are the differences between extruded and and expanded polystyrene (blue/pink foam vs. white "styrofoam") in regards to benchwork.

Is one less messy, stronger, in any other way better?

I only ask this b/c I've been offered the chance to buy some 2" thick styrofoam for benchwork, and in Texas, at least around here, the thickest blue/pink foam one can find is 1-1.5"...

Walkercolt

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #1 on: August 03, 2008, 01:48:43 AM »
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Stick with the blue/pink extruded stuff. The white beaded stuff is increadbly messy to work with, alot harder to shape, and then you need to cover the beaded surface with something to fill the cracks in it before it is decent for secnicing. Tried it, didn't like it, won't do it again. It will work for "building hieght", if it's covered with blue/pink foam, I guess. :P

Matthew Roberts

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #2 on: August 03, 2008, 01:56:58 AM »
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Okay. I've only used extruded before, or just plywood, so I haven't been able to have that experience.

DKS

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #3 on: August 03, 2008, 06:26:48 AM »
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In addition to being much less messy, the extruded foam is, inch-for-inch, much more rigid and doesn't require as much support. The beaded foam is softer and can sag.

Note that the brand name Styrofoam is, strictly speaking, the blue/pink extruded polystyrene insulation. Unfortunately, like Kleenex, the name has become synonymous with any kind of foam plastic, and the white beaded varity is not really Styrofoam. So when someone tells you they have Styrofoam for sale, unless you can see it for yourself, make sure they describe the matieral for you.
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Zox

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #4 on: August 03, 2008, 08:14:37 AM »
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I actually like the beaded foam. I find it easy to shape by cutting or scraping, and have never felt a need to coat it with anything more than paint and ground cover.





But I seem to be the only one.  :(

I do admit, I wouldn't use it for structural purposes--I wouldn't use it for a module top without a supporting layer of plywood underneath. Then again, I wouldn't use the other stuff without support, either... :)
« Last Edit: August 03, 2008, 08:17:54 AM by Zox »
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dwyaneward

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #5 on: August 03, 2008, 09:51:30 AM »
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What are the differences between extruded and and expanded polystyrene (blue/pink foam vs. white "styrofoam") in regards to benchwork.

Is one less messy, stronger, in any other way better?

I only ask this b/c I've been offered the chance to buy some 2" thick styrofoam for benchwork, and in Texas, at least around here, the thickest blue/pink foam one can find is 1-1.5"...

Matthew,

Look for a vault builder in your area they handle thicker blue/pink foam. There one here in the DFW area off of 35E in Lewisville, TX if your interested in a trip, Here their website http://www.southwestvault.com/home.html a local MRR work a deal so we could buy individual sheets. Just mention your a MRR and you can get the same deal.

I am trying ceiling tiles over blue/pink foam. Here a link to (photo's) a guy (Jim Six) that is a big supporter of this http://s22.photobucket.com/albums/b337/jsix/?start=all

Dwyane Ward
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Matthew Roberts

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #6 on: August 03, 2008, 02:58:49 PM »
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David, thanks, just what I thought, in both respects. As to branding, that also applies to Plexiglas/Perspex....

Zox, again thanks, but your pictures remind me why I don't like it... too beady.

Dwayne, Great! I'll have to look into that. Looks great. Ceiling tiles sound interesting too...

NSES40DC

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #7 on: August 05, 2008, 12:30:43 PM »
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I think you can use the white beaded foam as mountain or tunnel shaping only. I wuoldn't use it for benchwork.

cv_acr

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #8 on: August 06, 2008, 10:09:57 AM »
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We use the regular white beaded foam at the club for scenery forms; benchwork is all plywood. The foam is cut, shaped, and finished with a plaster coating.


Ian MacMillan

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #9 on: August 06, 2008, 12:21:40 PM »
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Home Depot or Lowes should be able to get you the 2" thick stuff as they have it in their northern stores. Ask a rep and they can order it for you, with no shipping charge.  They may require a min order though.
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Matthew Roberts

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #10 on: August 06, 2008, 12:38:20 PM »
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Ian, that was the problem, their minimum order is some HUGE number that I don't need, and very expensive.

wcfn100

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #11 on: August 06, 2008, 02:17:54 PM »
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Ian, that was the problem, their minimum order is some HUGE number that I don't need, and very expensive.

Here in AZ it's hard to get at the big box stores.  Everyone will swear that they've seen it, but they never seem to have bought any and it's never there when I look.  I had to locate a smaller building supply company and I was able to get individual sheets of 1/2" and 2" in the blue foam. If you don't mind a few fork marks on the sides, I would imagine you could do the same.

Jason

fieromike

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #12 on: August 09, 2008, 11:06:05 AM »
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Another good reason to use extruded foam over the beaded stuff:  Take a small piece of each type outside and hold a lit match under them.  The extruded foam will kinda burn as long as the match is there, but will extinguish when the flame source is removed.  The beaded stuff will ignite and continue to burn until it is gone (along with anyting else in the area!).

Nelson

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #13 on: August 10, 2008, 06:40:59 PM »
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The extruded foam will kinda burn as long as the match is there, but will extinguish when the flame source is removed. 

No, it continues to burn, and it burns faster and faster the hotter it gets, and sends off flaming drips and spatters as it burns.




Hyperion

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Re: Extruded vs. Expanded Polystyrene for Benchwork
« Reply #14 on: August 10, 2008, 07:00:17 PM »
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You can get the extruded foam with or without a flame-retardant additive.
-Mark