Help With A Crazy Idea For Slush Casting Urethane Plastic In The Actual Pepakura?


New Member
I have the crazy idea to slush cast the urethane plastic directly in the pepakura as apposed to rondoing inside it like a similar technique, as it may be an easier and sturdier alternative. No I'm NOT applying this directly to the paper, so don't worry. I'm giving you guys the basic rundown on it as I'll need as much input on this as I can get, and this isn't that common of a technique.

So this all starts with Blaxmyth 's modification to Hass Dardo 's reverse rondo technique [ Build the pep with the tabs on the outside, 2 layers of resin on the outside of the pep, at least 2 layers of wax on the inside of the pep as a mold release, slush cast 50/50 rondo mix inside the pep, fiberglass the rondo before drying completely rigidity, let it dry and peal off the pep after the rondo has shrunk from curing.]

So this is not such a common technique from what I've seen around here. I'm sure those of you who don't know of it may find it interesting, but I really believe that replacing the rondo/fiberglass with a slush cast urethane resin should work. In the same way a mother mold works, so does glassing the outside of the pep, and layering the wax on the inside of the pep works similar to a wax mold release. So then what's keeping me from just slush casting this thing?

Granted the pep I'll be casting is more complex than most, The N7 Helmet from Mass Effect, but even still, slush casting is slush casting. Now I'm no pro, as this is the first prop project I'm starting even after following this forum for a few years now, but that's why I'm here asking the pros.


So I'd like to discuss this, as I'm ready to move onto the next step after completing the pep, and I'm willing to buy a Smooth-On test kit and test this out, but if it's glaringly obvious this won't work at all or is too complex I won't go through with it. Again, I'm willing to give this a shot even if the results aren't that great, as you guys know there's always cleanup and touch up work after and pep work, and I feel this would be the best base to start with and minimize the mess work and fiberglass.

Let me know what you guys think, and thanks in advance.
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Sr Member
Looking forward to seeing the results! I don't have any experience with urethane, so can't really offer much help. Sounds like there is very little that can go wrong apart from the cost of the urethane. Good luck!

Mr Mold Maker

Master Member
Body work and sanding doesn't work quite as well with urethane resins, and they can tend to warp when exposed to heat, and shatter if dropped.

Fiberglass is good because it is relatively stable dimensionally, isn't as prone to warping (though it can and will warp on occasions!) And it just holds up to the abuse of finishing and molding a lot better.

This is obviously just my personal experience working with these materials, so your mileage may vary.. it's always worth a shot though, trial and error is how you progress in this game.


Well-Known Member
A few thoughts. The model (pep) will be very angular. When the helmet has been slushcast, it will require a lot of sanding. Body filler (rondo) can be sanded to a glass like finish if you spend enough time on it, but plastic? I would imagine it would ruin it. If you are prepared to spend a long time correcting this, then go for it. If time is a constraint, or the finish needs to be superior, I would advise against it.


Well-Known Member
Sorry,I posted the wrong videos. But somewheree in 405th forum, someone did this with ODST armor pieces a long time ago, it came out well


New Member
After doing the research I did come across a few people who have slush cast plastic in a pep before, granted the best thread I found didn't wax the inside making it harder to release, but it came out okay none the less. So it can be done yes, but like @blue2k said it seems that the rondo fiberglass system is more advantageous for additional work, while the slush cast plastic seems to be more suited for more simpler designs that require less fine work. It also seems like it would be best to fiberglass the insides if I decide to do this in the future.

So for this project it seems I'll be running with the reverse rondo system. I am happy to see this would work, I'll probably try it when I get around to making some ODST or Clone Commando armor in the future.

If anyone has anything more to share or present I'll be keeping an eye on the thread until it dies out.
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Sr Member
Looking forward to seeing some progress shots.

One thing I have found with the waxing the inside of the pep - two coats of wax is a minimum, plus make sure it is worked in well around the tabs. I place the tabs on the inside of the pep, as per normal building. Tried putting them on the outside, but it just feels weird... :unsure


New Member
Yeah, I put the tabs on the outside so it'll be easier to wax and even less filling across the whole piece. Sadly this is not something I'll be posting in the near future, as I've got something that needs more attention as of now. The reason I'm doing all of this now though is because I live in Illinois, and although I'm wanting to work on this through the winter, I need to get these steps out of the way now while the weather is still worm. I'll be working on this in my down time throughout the winter, so I probably won't start posting any of the progress work until January February. Don't get me wrong I'd love to start a thread and have people in on it, but I don't want to string people along for a year while I work on it slowly, so I won't start posting things until I've got a decent amount of work done to keep the thread from stalling out. I'm a real perfectionist, so this project won't be done until I deem it right. I'm not wanting for it to" be the best", as much as I just haven't found anyone who's done this helmet just right, there's always something off, and I'm doing this as a warm up for a subsequent project. So thanks again guys for all the help and input, I'm sure you'll see this pop up several months down the road and I'm looking forward to hearing what you guys think of it as I'm going along.
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