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Hello Haunters,

Had a question regarding expanding foam and Monster Mud that I thought someone might be able to help me with.

I have never used Monster Mud, but I have used expanding foam. Last year I built my mutant spider bodies out of expanding foam, but I ran into 2 problems.

1. When left to dry, the foam expanded and then split. I assume this was due to the outer portion of the foam curing while the inner foam continued to expand, splitting the outer shell. I handled this by wrapping the body in black duct tape at the time.

2. The second problem was after I had left the spiders hung upper during the day, I noticed the inner foam had shrunk from the surrounding duct tape (probably due to the Miami heat [not the basketball team]).


So, I was wondering if anyone else has had trouble with shrinkage of expanding foam, as well as if Monster Mud would help in stopping the shrinkage.

Does Monster Mud have any adverse effects on expanding foam? Dissolving it or anything?

I am looking at using the foam to beef up my tombstones and then layering with MM for a seamless look.

Thanks in advance

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Cute spider.

I don't know the full answer to your question but if you look up Stiltbeast studio's on youtube he does a video on expanding foam and he showed how you could cure it faster by squirting with water.

My experience with moster mud is it is mostly used to stiffen cloth and stuff . Not really for bulking up things. But I am sure other people here can help you more than me. And I have used it on foam with no problem but my foam was dry.

Ellie
 

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I used pink foam board to 'beef up' my tombstones. I used liquid nails to adhere the 2 or 3 layers. I then used another Stiltbeast Studios video and used liquid nails on the sides to smooth it out. Then finished it with a layer of drylok.
Monster mud might work for the sides as well, I just haven't done it.
 

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The thing under the bed
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You can try to spray your expanding foam in layers. Let the first layer dry then spray on top of that. once you have the desired thickness you can then cut and shape the body. If you try to make a huge ball all at once the curing process will vary.
 

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Going bump in the night..
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I've used a version of monster mud on top of expanding foam, and for the most part, it's done rather well.
(my version is a mix of plaster of paris and latex paint)

Here's the caveat (for me, at least): A witches head I did like this a number of years ago has become somewhat fragile, as the foam has shrunk inside, and left the outer shell unsupported in some spots. I've had to make repairs, but this may be her last season due to unavoidable decay.
 

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If your foam base is solid, monster mud could help define the shape and keep it that way, but if the foam isn't built up on itself, then the extra weight of the monster mud could cause it to collapse. The monster mud shouldn't react with the foam - I see all kinds of tombstones made from polystyrene that are covered in MM. Will you be using polystyrene sheets to construct the headstones, then adding expanding foam on top? I'm not sure if you're talking about creating the shape entirely out of spray foam or not.
 

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I have used monster mud over expanded foam in the past. It seemed to work, but over time it ended up cracking and breaking. It did hold the shape for the season but after storing it from one year to the next is when it cracked and broke. I tried to use Durham's water putty to fix the breaking and cracking. That has seemed to have worked so far. But I haven't seen how it held up in storage yet. When I used monster mud over the expanding foam I put the monster mud directly on the foam with out using anything for support in the monster mud.
 

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One part polyurethane, Great stuff etc, needs moisture to cure.
Apply it in layers, mist each layer very lightly with water.
Nothing (!) will dissolve cured polyurethane! Many years of exposure to UV and weather will degrade it however.
Anything filled with a large amount of one part poly will eventually collapse or deform, unless it was filled on a very humid day or was misted with water while being filled.
 
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