Author Topic: Is EPS foam packing material ok to practice on for sealing, sanding & painting?  (Read 5390 times)

magentawave

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I have some EPS foam that came out of a microwave oven box. (Its those EPS foam pieces that are formed to protect the microwave in the box.) I was wondering if I practiced sealing that EPS with spackle, and then sanding the spackle, and then painting it with acrylic paint would be similar to doing the same with the 1 or 1 pound EPS that I'd use to shape a board with? If it's not the same, or at least similar, then I won't waste my time doing this.

Thanks
« Last Edit: August 02, 2015, 12:21:02 PM by magentawave »
Pluto Platter: 7-10 x 29.25 x 4.25 x 114.5 liters

Biggreen

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I don't see why it wouldn't work just fine. Give it a try. Too bad I'm not closer. I'd give you scraps I'm getting ready to take back to the foam people.

surfcowboy

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I practiced it all including routing on Home Depot insulation foam. Got me ready for a blank. Do it man.

getcarter

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Yep...that'll work...the only difference with that stuff is that the bead spacing is much tighter as it's probably the 2lb variety. Generally, as foam density increases you'll need less spackle and your paint job will be more uniform. it all works !

GC

magentawave

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Cool. Thanks everyone. I'm used to polyurethane foam but EPS is a different animal. I took a DA sander to it with 80 grip paper and it sanded very nicely. I want to experiment with colors so I'll probably get some spackle and paint today.

How think do you put on the spackle? Is it obvious when you look at the blank that you've covered the entire surface with spackle? I'm asking because I'm wondering if it's difficult to see the coverage since both spackle and foam are white.
Pluto Platter: 7-10 x 29.25 x 4.25 x 114.5 liters

jrandy

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MW-

https://www.youtube.com/watch?v=tHHGxMAnLOU

Short little video from Stretch's shop showing it going on thin...just enough to fill in cracks and missing beads, not intending to create a shell or surface, which would need to be sanded off anyways.

Make sure it's lightweight and white, some come w/ primer and grey coloring that is miserable looking on a white board. Thin w/ distilled water (tap water is crap water, learned that and other things about spackle on Sway's) and let'er rip.

I hope to be dipping and scraping soon myself. -J

PS If you're planning on painting the foam before glassing, save some paint in case you need to touch up a sander gouge on a rail...
http://pushheretosavealife.com/
Be safe, have fun. -J

magentawave

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That was good to see. Thanks.

A few more questions for you please.

1) In the video it looks like he flipped the blank over immediately after doing one side. Is that true or will I need to wait for the spackle to dry before flipping it over to seal the other side?

2) But you do need to sand lightly after the spackle dries, right? If so, what grit?

3) Are there any different rules to follow when sealing 1 pound EPS?
Pluto Platter: 7-10 x 29.25 x 4.25 x 114.5 liters

PonoBill

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I make all kinds of stuff with blue foam and packing foam. It's fine. As far as spakling goes, make sure it's thin enough and very dry before you sand. You want spackle that looks like heavy cream.  Sure, you can turn the board over before it's dry, if your spackle coat is thin enough. You aren't laying on fill like taping a wall joint, you're filling surface defects on a pretty smooth surface.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

magentawave

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Thanks. I assume you lightly sand the rough areas of dried spackle later, right? If so, what grit? And how do you keep from UNSEALING what you just sealed?

I make all kinds of stuff with blue foam and packing foam. It's fine. As far as spakling goes, make sure it's thin enough and very dry before you sand. You want spackle that looks like heavy cream.  Sure, you can turn the board over before it's dry, if your spackle coat is thin enough. You aren't laying on fill like taping a wall joint, you're filling surface defects on a pretty smooth surface.
Pluto Platter: 7-10 x 29.25 x 4.25 x 114.5 liters

jrandy

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MW-When the spackle is dry...really dry...it sands very easily. When it is part dry it can get stringy and pull away from the substrate.

I'd start your experiment with 80-150 screen before spackle and 150-220 after, using a little foam between your hand and the screen, like an old rubber mouse pad or some heavy duty carpet pad or upholstery foam.  Also take a look at what surf supply places are selling for foam sanding blocks to get some more ideas.

Sometimes I just grab the next screen or paper I can find and test it carefully on the board. If it works I keep going, if not I keep looking.

Your microwave EPS is probably molded and the beads may be fused smoothly at the surface. If you want to get a full appreciation for the nature of the beads, cut off a chunk with a hand saw and shape/sand it back smooth and then spackle it.

-J
http://pushheretosavealife.com/
Be safe, have fun. -J

magentawave

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Thanks again. Yes, the foam is molded so I'll cut off a chunk and experiment with planing and sanding it. I'm going to practice sealing it and coating with acrylic paint too.

Do the foam beads absorb resin and thus require sealing, or is it just the spaces between the foam beads that require sealing? Or is it both?
Pluto Platter: 7-10 x 29.25 x 4.25 x 114.5 liters

jrandy

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Hi MW-
As I see it,  spackle fills in the cracks and fills in missing beads and is then sanded off the faces of the beads.

Some pictures to illustrate. Samples are 1 PCF EPS treated with a green silkscreen ink to simulate spackle or resin.

The ink does not do much on the face of the beads, but does go into the crack, voids, etc.

Have fun with your trials and looking forward to seeing your build in the Shape Shack! -J

http://pushheretosavealife.com/
Be safe, have fun. -J

magentawave

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I get it now. Thanks!
Pluto Platter: 7-10 x 29.25 x 4.25 x 114.5 liters

 


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