[Spats]

Technical question on expanding foam, particularly Great Stuff--

Let's say you want something with a foam exterior but you don't want the lines a can of Great Stuff gives.
Can you smooth it with a plastic knife while it's still curing? What sort of textures can you achieve with wet Great Stuff? Can it be smeared around while wet?
Do you have to wait until it dries, then carve or sculpt it then with a sharp edge or a toothed blade?

I'm hoping for an irregular rocky surface, and this particular project needs to be completely hollow and riddled with cracks and holes, so I can't make paper mache or paper-and-tape rocks. I'll use paper mache clay if I must, but I'd rather avoid it.

 

[Bubbels]

When its wet it would be like trying to mold ecto plasm. You can carve it and sand it though. I havn't done any great detailed work with this, but my skulls I made in a mold always require some excess to be cut off.

 

[Mr_Chicken]

There is actually a phantom time just before it solidifies when you can (with gloves or a stick or something) pull and push it smooth. That's how I did the neck and shoulders of this guy: DSCN8746.JPG (image)

 

[Frankie's Girl]

There is actually a phantom time just before it solidifies when you can (with gloves or a stick or something) pull and push it smooth. That's how I did the neck and shoulders of this guy: DSCN8746.JPG (image)

Mr. C, your talent never ceases to amaze me.

I'm going to have to play around with the great stuff some more. I've used it recently for mortar fill on a styro well prop I'm building, and while it looks decent enough, I would have liked to get in there and smooth it a bit more instead of it being more on the blobby side.

 

[Lurks in the shadows]

Manipulating the foam during the "Phantom" time is tricky. Too soon and it sticks mercilessly, too late and chunks can rip out or it's just too rigid to reshape.

I use rubber gloves with a smear of vaseline all over them. Then I dip my fingers in water before shaping the foam. After the foam is cured, a little soap and water is needed to remove any vaseline residue so paint will adhere.

 

[Hauntaholic]

Hi everyone.
When I built my spider I "sprayed" great stuff into a stream of compressed air utilizing an air blow gun. Same concept as a web shooter. It deposits the great stuff in small splatter spots that then expanded and left a texture like a brain or a hedge apple. You can vary the amount of air pressure and the distances as well as the number of "coats" to achieve the desired effect.
Just be sure to mask off anything you do not want textured.

 

[Spats]

Lurks,

Is it possible you could give me a ballpark estimate on the time? Nothing exact, just a window to look for. Like I said, I'm going for a rocky texture, and I don't have an air compressor. If I have to, I suppose I could buy some canned air, but I'm interested in doing this without too much splatter.

 

[Mr_Chicken]

Try checking it every half hour. Give yourself a few test blobs to work with so you can try forming it periodically. I think it's somewhere between 1 hr and 2.5 hr.

 

[coffen cats]

What do you line your mold with to keep it fro sticking to it ?

 

[Lurks in the shadows]

Spats: As Mr. C says, the time varies. It'll depend greatly on how humid it is. Test blobs are a really good idea!