Anyone ever used Great Stuff foam?...

[Aeon]

I'm looking to use Great Stuff to fill a few molds I made. I wanted to reinforce the interior (as they are hollow) with Great Stuff foam to make a buck for vacuum forming. Has anyone ever tried this?

I'm trying to avoid having the foam over-expand and cause my hollow molds to erupt and break.

Any tips on accelerating curing times would be helpful too. I read on GS's official site that mists of water helps the curing process.

Thanks in advance guys!

 

[Firefoxm31]

Howdy,
well I used it tonight for an adhesive for my styrofoam laminating proceedure for my halloween costume for me and my wife. We're going to our annual Disney Holloween party as a Disney Haunted Mansion "Doom Buggy", lol... it's about 3/4 the size or the real one. They are expecting me to outdo my costume from a couple years back when I came as a Jungle boat
so anyway, I'll have an answer as to how tough this stuff is tomorrow.
Best,
Will

 

[exoray]

I'm trying to avoid having the foam over-expand and cause my hollow molds to erupt and break.

This will be your biggest issue, I highly recommend doing it in thin layers and (for a lack of a better word) multiple locations of blobs, rather then trying to do it all in one large fill...

The stuff expands in all directions and easily triples in size...

Say you filled a cardboard box, don't assume it will just expand up and out of the box... It will actually expand into the sides and bottom of the box as it drys and possibly deform any locations that can't take the pressure of the expansion... Your box would probably have no flat surfaces but rather bulging sides and a bottom...

 

[Robot Monster]

I have seen version of other foam products that are a non-expanding foam. It might be helpful where overfill is a problem. I think DAP makes it, comes in a blue can the last time I looked.

 

[Aeon]

I used Foam-It by Smooth On in the past for casting molds and it worked great. I know that it just fills up and out of whatever shaped boxes I made with it and didn't over-expand like it does with Great Stuff.

I was thinking of using bungie cords or rubber bands to hold my pieces in shape to avoid deformation, but it's going to be unusually hard to do that considering that the shapes I made aren't exactly conventional shapes (bc they're body armor)... I gave the thought of lining the inside surface area of the hollow molds using duct tape first to somewhat contain the foam to a certain extent and then attempt to go around the surface area from the outside perimeter towards the center with little layers at a time as Exoray suggested.

What do you guys think?

 

[stormtrooperguy]

great stuff has 2 varieties, at least in my area. a red can, and a blue one. the blue one is about $2 more than the other. it is designed to not push out on the sides as it cures. it's meant to fill gaps around windows, so it won't bow the window and keep it from closing right.

this is the stuff i've used and have been pretty happy with it.

 

[Aeon]

Thanks TK!!

 

[exoray]

great stuff has 2 varieties, at least in my area. a red can, and a blue one. the blue one is about $2 more than the other. it is designed to not push out on the sides as it cures. it's meant to fill gaps around windows, so it won't bow the window and keep it from closing right.

this is the stuff i've used and have been pretty happy with it.

From my experience the blue stuff never gets hard (rigid) it stays more foamy like couch cushion foam, without the the rebound... So I don't think it will be of much use for creating a vacuum form buck...

 

[LordFett]

great stuff has 2 varieties, at least in my area. a red can, and a blue one.

3 kinds actually. There is a black can too. We carry all 3 at my Home Depot. I've only used the expanding stuff and am not familar with the other two at all.

 

[Firefoxm31]

ok great stuff foam is too soft to use for a core for a buck for vacuforming it's more like a nerf foot ball.worked great as a glue though

Will

 

[Aeon]

I had some other alternatives in mind for packing some rigidness into the molds. I was thinking of just cramming in some clay that's tightly packed. I'll let you guys know what I end up doing and post some photos.

Thanks guys!

 

[exoray]

I had some other alternatives in mind for packing some rigidness into the molds. I was thinking of just cramming in some clay that's tightly packed. I'll let you guys know what I end up doing and post some photos.

Thanks guys!

Why not just fill the shells with Plaster of Paris? It's cheap and plenty hard...

 

[Aeon]

Why not just fill the shells with Plaster of Paris? It's cheap and plenty hard...

Well the molds are being done out of mat boarding. The material tends to absorb all the moisture from the plaster while its curing... so I usually end up with a wet, rotting mold. I tested a few different ideas a while back. I've also used Foam-It in the past for vac form bucks and they work great. I know the Great Stuff formula is similar to the Foam It product, except that the Great Stuff deforms the molds.

I would sculpt the armor in clay and cast fiberglass molds, but I'm currently working out of a small apartment, so the ventilation is a no-no for me at the moment.

Thanks for the input guys. I appreciate it.

 

[Drago Lordist]

fairly be ye warned!!!!

WEAR GLOVES
the one time I used the stuff I didnt and the cap broke off towards the end getting all over my hands. I had glued my hands together as I tried to pull my other one off the bottle. were it not for my instructor having come across the same problem before I probably would have gone to the hospital to find a way to get the stuff off my hands and to get my hands apart for that matter. WEAR GLOVES!!

 

[ytt1300]

i've used it to fill an already vacformed part, and it works great to lend rigidity, the trick with this kind of foam is to control the pressure it is going to expand under, if you fill a bowl with it, it's gonna expand in the direction of least resistance [up and out of the bowl], if you are limiting a direction of resistance [a bowl with a lid and small hole in the lid], it's gonna bow out, unless it is being held in a more rigid container. the only way you could get the great stuff foam to be hard enough to vac form over, would be to create a rigid negative shape, then leave a very small relief area, that way the pressure within the enclosure is greater, and makes for harder foam, but to make the enclosure robust enough, may be as much work as making a buck from scratch for vac forming... I've now switched from the great stuff foam, and am using a product from tap plastics [which may be an overpriced, re-branded smooth-on product] called X-30, it expands THIRTY times the original volume of liquid, and, as I stated earlier, if i put it into a rigid container, I can get very hard foam, that is carvable, or vac formable

[and as stated before, wear gloves! also you can clean up UNCURED foam with acetone, after shooting some great stuff, I take off the "trigger and tube" and drop it in some acetone, to keep it clear of hardened foam]

 

[DragonLady]

I have personally used Great Stuff foam for my props. I spray the foam with water before it starts to cure. It expands less,cures faster & less holes if you plan on cuting any it off. So far I have made 2 different Monster Hunter weapons using this method.

 

[danbakeronline]

I've seen Great Stuff foam used in a couple ways, good and bad. I personally have carved out of it, with mild success. You still have to do a LOT of puttying and cleanup for it to look anywhere decent.

The worst I've seen was on a friend's R5 unit. He used it to back up the styrene in the dome. Great Stuff is an architectural foam, so it's designed to skin itself hard, then use that hard shell to force its way into the cracks in your foundation. That's exactly what it did to that poor R5 dome too. It split apart every single seam, bubbled out like it was alive, then hardened. Nothing would go back together correctly after that, and he had to start over.

If I were you, I'd back it up with a non-architectural foam. There are two main types of foam: rigid and flexible. You can make that choice for yourself depending on what you want the finished product to feel like or withstand.