I tried filling some gaps on my polar bear with gray foam clay and now it has gray/black streaks running down from the areas where I put the foam clay. I'll try and get a pic of it this week and post it next weekend. The foam clay wasn't staying in the gaps so I gave up and tried to dig it all out but it appears that I didn't get it all, that's where the streaks are coming from.

So from my experience it's not holding up too well. I suppose one could say that it hasn't cured in the 9 months that it's been in there because it's stuck in a crack and couldn't dry? But I think I'm being awfully generous with that. Mind you, I've only had the prop outside for two weeks now.

 

Hmm. That's disappointing. I was hoping to use it to sculpt a face for an animatronic so it would be as light as possible and might hold up better than a latex mask down here in GA. Thanks for the info!

 

Here’s that pic I said I’d take. But I suspect that if you coat the foam clay with plasti-dip & then paint it might be alright.

 

I have used wood epoxy foam on the siding of my house. Dealing with dry rot on my porch, which it was designed for. It has worked out well. Of course in Florida's 99% humidity I let it dry for a couple of days and not hours before I paint it. No problems with weather. I also use it on my outdoor props and sculptures. I use for fine detail work on my foam sculptures. Once again I let it dry for 2 days before I paint it. I have never had the problems you are describing. Not sure what would cause that. Bad putty? I have run into that problem of normal epoxy not drying, but not wood epoxy. Foam Clay, is that foam wood epoxy by another name? Anyway if its something different try foam wood epoxy its available of Amazon, I think you'll like it.

 

Foam clay is a type of moldable EVA foam that can be cut, sanded, and drilled after it dries. It is very lightweight and flexible and is used in costuming and props a lot, which is why I thought it might be a good fit for an animated prop so it wouldn't cause too much strain on the motor used. But it is water-based, so I was afraid it might not hold up well. It still might, if it's coated in something protective like Plasti-Dip before painting.

But all that to say, I will look into foam wood epoxy! Even if it isn't a good fit for this project, there are always others.