Tutorial: Using Casting Resin For Your Pep Build

Ruze789

Well-Known Member
Using casting resin - liquid plastic - to harden your helmet or armor project:
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Apologies for the wordiness of this tutorial, but I'm hoping that more text now means less answering the same questions over and over later.

Many thanks to spartan051 who answered all of my questions before I started doing this.
After I saw his SC300 MC helmet I was inspired to try this out, and he was a big help.
Here's his build thread: Spartan051's SC300 Mk VI & Recon WIP thread
And here's psberetta's thread: psberetta's Casting Resin Rogue helmet thread

For related videos, especially if you have no knowledge of resin, you should certainly check out:
Smooth-On Youtube Channel
Smooth-On Smooth-Cast 300 Video
Adam's Casting Video

Before I start:
I know, I know what’s coming, that’s not Halo!! I’ve been asked by a couple people to write up a tutorial on using casting resin, and this is the project I used this method on. When I end up doing this with a Halo-related project I will swap out the pictures; until then it’s Star Wars. This is Boushh, Leia’s disguise from ROTJ for anyone who might not know.

Preparation/ Before you resin:
-- Assemble your pepakura file. You’ll need supports, too. If the pep file you built didn’t have any, then come up with some – cardboard, cardstock, whatever you can use to keep your build as straight and square as you can.
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-- Make sure to close off as many gaps as possible in folds – small holes are fine, but any noticeable spaces should be covered. I used clear scotch tape on the outside and it worked out pretty well for me. Just make sure to get the tape as flush and smooth as possible, otherwise the resin will leak a little – it’s still not a big deal, it can be sanded right off.

-- Any open areas, such as a visor or holes for vents, need to either have a temporary piece put in place that will get resined and cut out afterwards, or build a lip around the edge. If you don’t do one of these things your resin will just pour right out the opening.

-- Make sure to set up everything you’ll need beforehand. It will make everything go much smoother for you.

-- Here’s what I used:
Portable table
Plastic to cover your table (it might be a good idea to lay plastic/ newspaper down under the table and in your work area, this can get pretty messy)
Smaller plastic containers or disposable cups to measure the resin in
Plastic container (or several) to mix the resin in
Paint stirrer or similar item for mixing resin
Casting Resin – I used the trial (16 oz bottle sizes) size of Smooth-On Smooth-Cast 300.
Latex gloves

-- I used clear plastic disposable cups for measuring. The easiest way to mark them (if you use disposable cups) will be to get a measuring cup that uses liquid measurements, add water to the measuring cup in each amount you’re looking for, pour that into your disposable cup, and mark it. Make sure to label each measurement if you make several marks. I marked mine at 2 oz and 4 oz.

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Now on to the fun stuff, Resining:
-- You’ll want to start with small batches of resin; if you pour too much in at a time you’ll run the risk of warping your cardstock in ways that are not at all pleasant to fix. I started with 2 oz measurements.

-- Pour 2 oz of Part A into one of your measuring cups, and 2 oz of Part B into your other cup. Now pour them together into the larger mixing container and stirrrrrrrrr. Make sure it is evenly mixed or you may run into curing problems.

-- Pour the resin into your helmet/ armor piece. Only on the inside, the outside does not need it. The first coat of resin in your helmet needs to be spread fairly thin, this will allow it to soak into the cardstock and begin to harden your helmet before you add the thicker coats. Slush the resin around, making sure you don’t let it sit in one spot for too long. You will know as soon as it starts to kick, it will move around much less and turn white/ opaque.

-- Repeat the 2 oz + 2 oz parts until you’re happy with your first thin coat. Don’t wait too long between coats - though I didn’t have this problem I’ve seen it said that if you allow too long between them the coats won’t stick together properly and your piece will delaminate… The layers of resin cure as totally separate layers instead of one cohesive cast. You shouldn’t have a problem with it as long as you aren’t off taking long breaks between coats. Just don’t go taking a lunch break when you’re halfway done with this.

-- After the first thinner hardening coat is done, you can step up the measurements if you wish and start mixing 4 oz of each part at a time. I never went any higher than that, this is only paper you’re pouring the resin in to. The first coat is a little stiff by now but not fully hard, pouring too much in at once could still warp your project.

-- Repeat as needed or until you run out of resin. The thickness is up to you, whatever you’re comfortable with. You’ll want to shoot for 1/8 to ¼ inch thickness all around for a decently sturdy helmet. I came up just a little bit short on mine so I had some pretty weak areas, mainly around the lower edge/ rim.

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-- Now find a nice safe place to let your helmet/ piece cure. Not sure the cure time exactly, but I let mine sit overnight.
 
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Ruze789

Well-Known Member
(Continued)

That's it for the resining! On to the other stuff:

-- My helmet ended up a little weak in a couple of areas since I ran out of resin, so it required additional reinforcement. I went with normal fiberglass resin with fiberglass cloth, one or two layers around the inside bottom edge of the helmet. The tutorial for working with fiberglass resin is in the pepakura section if you need it. http://405th.com/forums/index.php?showtopic=2234

-- Now, the paper and smoothing part. I started to run far behind on this project, so I didn't get to do half of what I wanted to. I started by sanding the hard, sharp folds of the cardstock with my Dremel. If your resin is thick enough, you can sand all the way through the paper and start to sand the resin. This will later cut down on the bondo work required.
**A note: sanding casting poly resin does create harmful dust. Remember to wear a mask!
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-- It might be in your best interest to remove all cardstock from your project now. I'm not sure the best way to do it since I didn't get a chance to, perhaps someone can chime in. It can be sanded off, and I've seen it mentioned that you could soak it in water to loosen up the paper - but I haven't tried either way so I can't say what works.
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-- Apply bondo or your smoother of choice, with my time running out I went with wall joint compound / spackle. I hate working with that stuff and this will likely be the last time.

-- Add smoother, smooth, sand, repeat until happy - or till you run out of time.
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-- Paint, add greeblies, visor - finish as required.
Please excuse the unfinished-ness of this one, Halloween came up quick!
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If there are any questions, please post them in here - there are quite a few people who can answer casting resin questions.
 

JangoFett140

Active Member
great tut!! i think ill try this if the price is right!!
thanks for taking the time for this!!

Edit:How much did you use? if you said sorry i missed it.
 

ilikecats

Member
Congratulations on a fine tutorial, I hope this gets stickied soon.

On a side note, any explanation of why the casting resin is a volumetric 1:1 ratio? This is just for general knowledge of course, but I just like to know these stuff.

Also, any tips on working with Weapons?

This is obviously only for my own interests, and does not hinder the comprehensiveness of this nice tut.\

So nice work!
 

JediStumpy

Well-Known Member
Awesome! Great pics too!! I think this method is great! Might be a little less forgiving but seems easier. Plus you know that the plastic (resin) is just of strong and tough as FB.

QUESTION: Why do you have the remove the cardstock? (all of it?) I understand that the card stock is still the outside layer after you SO300 resin the inside but couldn't you just use FB resin to "paint"the outside like when you would use the FB method? That way you seal the paper. Now I guess that if you were to drop it, heaven forbid, you might crack the fb resin of the outside,( and bondo) that that might be a downside. So is it possible (I haven't looked at the Smooth On webiste in a while), that there is a thinker (or thinking agent) so you could possible brush on a thin layer or two to "seal" the paper?

I guess this wasn't a question, but more of a discussion topic for this method.
(sorry if it sounds like I'm bashing the method, but I truly am not. I really think this is a great idea!)

2nd Question: Was the trail size of SM300 enough resin to complete the process or is more needed?
 

Ruze789

Well-Known Member
Thanks guys! I meant to write this up quite some time ago but just never managed to free up any time till now. Hope it helps answer some questions.

JangoFett140 said:
Edit:How much did you use? if you said sorry i missed it.
16 oz. bottlesof each Part A and Part B, 32 oz total

ILikeCats said:
On a side note, any explanation of why the casting resin is a volumetric 1:1 ratio? This is just for general knowledge of course, but I just like to know these stuff.
Also, any tips on working with Weapons?
I'm not sure what goes into it, but it seems like most casting resins I read about are formulated to be 1:1 and is usually a selling point they'll stick into product descriptions. It is much nicer and easier to mix 1:1 rather than 20:1 or something similar.
As for weapons, I haven't tried yet so I don't have any advice, but I suppose you could cut a hole into a pep weapon, pour some casting resin in and slush it. You'd just have no way of knowing if you are spreading evenly.

cgspartan said:
very interesting method. Almost like using your pep piece as a one-time disposable mold.
Yes that's the idea of it. I like the way it worked out and will be doing it again.

JediStumpy said:
Awesome! Great pics too!! I think this method is great! Might be a little less forgiving but seems easier. Plus you know that the plastic (resin) is just of strong and tough as FB.

QUESTION: Why do you have the remove the cardstock? (all of it?) I understand that the card stock is still the outside layer after you SO300 resin the inside but couldn't you just use FB resin to "paint"the outside like when you would use the FB method? That way you seal the paper. Now I guess that if you were to drop it, heaven forbid, you might crack the fb resin of the outside,( and bondo) that that might be a downside. So is it possible (I haven't looked at the Smooth On webiste in a while), that there is a thinker (or thinking agent) so you could possible brush on a thin layer or two to "seal" the paper?

2nd Question: Was the trail size of SM300 enough resin to complete the process or is more needed?
Thanks!
If you want to, you could leave the cardstock. The trouble with it might be that when you only sand away some of the cardstock the sanded areas have a terrible texture that don't go away unless you add more smoother over it. The transition from cardstock to plastic looks bad, I tried to take a couple macro shots of it above. You may end up using bondo in areas that shouldn't need it, just because you need to cover up the sanded cardstock. Or you could use FB resin on the outside and finish it just as you would finish a regular Fiberglassed helmet.
It may be possible to use a thin layer of SC or other poly resin to coat the outside, after you've slushed the inside. I have seen one or two propmakers who said they like to use small batches of poly resin on the outside for smoothing, plus it leaves a nice glossy finish.

And to your second Q: It was not quite enough for my helmet. I would have been happy with another 4 oz of each part (8 oz total) but ran out. I will definitely get at least the 1 gallon kit for my next project(s).
 
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Spartan 051

Well-Known Member
I would have to disagree with you on removing cardstock.

Ive never removed the cardstock and went straight to sanding and smooth stage. I personally like having the card stock on the helm. Like with my Mark VI i used the lines ans a guide were to smooth/sand

Mark VI with cardstock still on:
IMG_2726.jpg
 

S1l3nt V1p3r

Sr Member
I believe the removal of the card stock is optional, and a choice every caster can make. What ever your decision is, the outcome is still the way you want it to be.

But this is a great tutorial/How-to Thread. ^^ IF I can get a hold of SC300 here in Norway, I'll try this method on my ODST Helmet. (Ooops, did I just say that out loud? :rolleyes )
 

Ruze789

Well-Known Member
Spartan 051 said:
I would have to disagree with you on removing cardstock.
Ive never removed the cardstock and went straight to sanding and smooth stage. I personally like having the card stock on the helm. Like with my Mark VI i used the lines ans a guide were to smooth/sand
That's a good point, I'll edit to reflect that.
For my project, it might have been easier to remove all cardstock than try to get rid of the terrible texture difference.
Since my next helmets will most likely have no time constraints I'm hoping to be able to try a few different things on them; leaving the cardstock on, taking it off, using small amounts of SC on the outside. This one just ran out of time for smoothing.
 
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Remraf

Active Member
Would this method work on pieces that have been coated with fiberglass resin on the inside and outside? What about pieces that already have fiberglass on them? The reason I ask is because I have two pieces that already have a resin coating, and a helmet that is partially fiberglassed.
 

Sisko4

Well-Known Member
I must say that this Method of Hardening is a clean and easy Way when you only can work inside!

Today i´ve used it too and mixed the first Layers with some Fiberglasflour, then i added some Fiberglassmats and it worked very good! At last i filled the inside with pure Plastic Resin for a smooth Surface on the inner Side and brushed the outer Side too, it looks perfekt after sanding!

No Toxic Smell like the normal Polyesterresin, plus the Surface dont stick a long Time after hardening!

Short sayed its like building a OneTimeToUse-Mold^^

Would this method work on pieces that have been coated with fiberglass resin on the inside and outside? What about pieces that already have fiberglass on them? The reason I ask is because I have two pieces that already have a resin coating, and a helmet that is partially fiberglassed.
I think that should be no Problem! I´ve done this too in Summer on a Helmet for the inner Surface, veryyy smooth after a very little sanding!
 
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GeneralMayhem

Active Member
I've been using the same method for my armor parts. I've found that a light application of Vaseline allows the paper to be pulled off quite easily. Also, I found that a thin pour of 2 part urethane foam after the layer of resin is an effective low cost reinforcement while adding a negligible amount of weight to the form, making it easier to handle/detail without fear of crushing it.
 
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