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keep foam from flaking - but BORING

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Bob Cole
keep foam from flaking - but BORING
on Apr 21, 2014 at 6:09:53 pm

This could win the award for Most Boring Post but here goes anyway:

I'm using an old Halliburton case to consolidate all my 4" filters and matte box. It's been a long time since I've used a case that has the pick-n-pluck foam, and I especially don't want it to start flaking and shedding around my filters (even though they all have their own sleeves).

Does anyone know of a good way to make protective foam a little harder, a little less likely to flake, on the inside edges?

As I warned, pretty boring!

Thanks.

Bob C


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Jason Jenkins
Re: keep foam from flaking - but BORING
on Apr 21, 2014 at 6:59:09 pm

I haven't tried it, but I wonder if Plasti Dip spray would work well for that application.

Jason Jenkins
Flowmotion Media
Video production... with style!

Check out my Mormon.org profile.


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Mark Suszko
Re: keep foam from flaking - but BORING
on Apr 21, 2014 at 7:17:47 pm
Last Edited By Mark Suszko on Apr 21, 2014 at 7:19:40 pm

Well, I think this might work: Water-based polyurethane, I'm partial to Minwax.

We use it in the RC model airplane hobby, to toughen-up EPS (Expanded Poly Styrene), as well as other types of foam, like expanded polypropylene, so it will take any kind of paint without melting..., adding fiberglass cloth, and some talcum powder as a filler for the weave between coats of the Minwax, we can even create lightweight, rock-hard contoured finishes that look like metal... but even without adding fiberglass cloth or talcum powder, I believe the WBPU will also add a bit of wear-resistance to other foams, like instrument case lining. I would brush it on a sample, or the back side of the foam, as a test, using disposable brushes from the dollar store. Brushes clean up with plain water, if you don't let them dry out first.

ATTENTION: Be sure it is the WATER-based polyurethane, nothing else will do. A half-pint can is around six bucks, you might find it in a spray as well.



There's also a method to create new custom form-fitting shipping case liners, using that "great stuff" expanding foam in a can. You lay a sheet of heavy "visqueen" plastic in the case, spray in the expanding foam, drop a second layer of the plastic sheet on top, then lay your (protected in saran wrap, just in case) components into this "nest" and let the expanding foam rise and contour around the objects until it hardens. Beware, Great Stuff and all expanding polyurethanes are The Very Devil in terms of stickiness, and you'll need acetone at the ready to clean up spills before they harden and become impossible to remove. However, if it doesn't leak out onto anything during expansion, the double-layer plastic sheet sandwich creates a conformal liner that is removable at any time, and also trimmable with a blade. Some high-end computer gear is shipped, packed in this way, which is how I discovered the technique. If you are paranoid about getting stuff stuck to the gear, weighted cardboard or wooden forms/ templates of it are almost as good, during the forming process. Don't over-apply the foam from the can because it DOES expand quite a LOT... :-) You might want to do a small test first using a shoebox, sheets of plastic tarp, and some unimportant, inert object with a funky shape.


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Bob Cole
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 1:24:28 pm

Good suggestions. Thank you. I wonder whether Great Stuff is too rigid to be a good cushion.

I also wrote to Pelican, who replied "Due to the nature of the polyester foam it will pill over time with the placing and removal of objects. We have suggested that after the foam is actually cut to your specification you place a thin sheet of gauze over the area that can be glued down with a spray adhesive." (By "gauze" they mean fabric, not bandages.)

I think I'm remembering why I don't like foam!

Bob C


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Todd Terry
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 2:31:23 pm

I've been trying for YEARS to figure out how to cut my own custom foam, but have yet to have total success with that (at least results that are both functional and look pretty).

When buying some upholstery foam a few years ago I remember seeing the guy at the store cut it with a jigsaw...clean as a whistle. I don't know what kind of blade he had (it was also very long), but haven't been able to replicate the cleanness of his cut.

The last time I was at good 'ol Harbor Freight Tools buying some widget for a shoot I noticed they sell a hot knife... I might give that a try the next time I'm in need.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Mark Suszko
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 2:41:52 pm
Last Edited By Mark Suszko on Apr 22, 2014 at 2:44:55 pm

I own that hot knife from Harbor Freight; it's too heavy-duty - more for cutting things like linoleum tile and plastic sheet.

What you want, Todd, is a hot-wire foam cutter. They come in wand style, (available from craft stores like Michaels or Hobby-Lobby, and the American Science and Surplus Center) - and the bow style, available in the railroad scenery department of a high end hobby shop.

You can make your own hot wire foam cutter, using a taut strand of nickel-chromium "nichrome" wire, attached to something like a hacksaw handle, and for the DC power supply, a car battery charger, model train transformer, or wall wart and adjustable resistor for the heat control. I own three of these as part of my RC airplane hobby, I make a lot of my own planes out of foam. My heavy-duty cutter looks like a band saw, and is powered by a surplus variac. But for cutting foam for your instrument cases, the wand-type will be fine. Nichrome wire used to be available at RadioShack; I think you can still score some at tower hobbies online. Try something like this, it's all put together for you:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKT85


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Todd Terry
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 3:07:49 pm

Good to know about the Harbor Freight knife, Mark. I didn't even look at it, just noticed the sign on the shelf that I passed.

You can also find quite a few nichrome wire cutters on eBay (or you could in the past), and I've seen DIY plans through the years... but never got quite that industrious (or bored).

Also, it seems to me that their function limits their usability. Don't they, by design, have to be a wire stretched between two other things? Forgive my ignorance if that's not the case. If so, that really limits the usefulness... at least for things I need to cut. Say you want to cut a smallish round circle in the center of a piece of foam for a lens... well, you have to get the wire inside the circle first. So, lets say you can cut a rough hole first, disassemble the knife, and put it back together with the wire through the hole. Then you have to have a frame for the wire with a "throat" deep enough to reach. Gotta be a better way.

What would be ideal is just a handle with a single rigid hotwire sticking straight out from it... but I know it doesn't work that way.

Hmmmm...

I've also thought it might work to soak foam in water and freeze it... you could get a good clean cut with a fine-tooth saw blade (or a knife) if the foam was frozen. But then you have a sopping wet piece of foam, and foam takes forever to dry.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Mark Suszko
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 4:04:38 pm

The wand style foam cutter is a single thin rod like a fencing foil... or, imagine a soldering iron, but with a thin, foot-long rigid wire tip. With that, you can do slow inside cuts without the tedious diss-assembly and re-assembly of a bow. I've gone thru two of these type cutters: they are cheap and fragile: i loaned the first one out to my kid for school, and his friends bent and broke the thing in a day. You'd be more careful, so it would work better for you. Work slow, don't force it, or you'll bend and break the heating element.

http://www.ebay.com/itm/like/191133334060?lpid=82



If I have to do inside-cutting, coping-saw style, I make a pilot hole with a plain old used low-power soldering iron reserved for the purpose, then put the bow to use... the end has a quick-release kind of system so it's really not a huge deal.


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Mark Suszko
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 4:08:43 pm

BTW, costume makers who use thick foam rubber sheets often say that a used electric carving knife from the thrift store does a great job for the initial rough cutting.


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Todd Terry
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 4:12:07 pm

YEP I 've tried an electric carving knife, too... pretty jagged results.

I might have to pick up one of the single-rod wand-style knives sometime. With any luck I might be able to make it last 50% longer than a school kid. Nah, probably not.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Bob Cole
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 4:16:23 pm

Mark, does the hot knife help to solidify the foam and prevent pilling?


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Mark Suszko
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 4:29:27 pm

No, the knife or hot wire only makes clean cuts; it doesn't seal anything. To solidify the foam or stop pilling, try the water based polyurethane varnish I suggested, or a spray can of artist's clear fixative, but be careful of the fixative having volatiles that can melt the foam... apply it in very light mist coats, letting each coat dry before continuing. You might even try Elmer's white glue, thinned with water and brushed on.


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Mark Suszko
Re: keep foam from flaking - but BORING
on Apr 22, 2014 at 4:24:36 pm

Local craft stores tend to stock 'em near the floral arrangement sections. They come in AC wall-wart versions, and a few times I've seen hand bows driven by two "D" batteries in the handle, but they look flimsy.

American Science and Surplus has the wand cutters in a recent catalog. If you're unfamiliar with AMSCI, they are also known as the "mad scientist store", with a lot of industrial and scientific /educational surplus items great for use in movie props, costuming, or "Maker" projects. They are what the old Edmund Scientific catalog used to be like.

page 52, item 93201


http://www.sciplus.com/Catalogs/2014-May/#52

You're welcome:-)


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